* [PATCH v6 01/10] x86/acpi: Add helper functions to setup and access the wakeup mailbox
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri,
Rafael J. Wysocki, Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
In preparation to move the functionality to wake secondary CPUs up from the
ACPI code, add two helper functions.
The function acpi_setup_mp_wakeup_mailbox() stores the physical address of
the mailbox and updates the wakeup_secondary_cpu_64() APIC callback.
There is a slight change in behavior: now the APIC callback is updated
before configuring CPU hotplug offline behavior. This is fine as the APIC
callback continues to be updated unconditionally, regardless of the
restriction on CPU offlining.
The function acpi_madt_multiproc_wakeup_mailbox() returns a pointer to the
mailbox. Use this helper function only in the portions of the code for
which the variable acpi_mp_wake_mailbox will be out of scope once it is
relocated out of the ACPI directory.
The wakeup mailbox is only supported for CONFIG_X86_64 and needed only with
CONFIG_SMP=y.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Fixed grammar error in the subject of the patch. (Rafael)
- Added Acked-by tag from Rafael. Thanks!
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- None
Changes since v3:
- Squashed the two first patches of the series into one, both introduce
helper functions. (Rafael)
- Renamed setup_mp_wakeup_mailbox() as acpi_setup_mp_wakeup_mailbox().
(Rafael)
- Dropped the function prototype for !CONFIG_X86_64. (Rafael)
Changes since v2:
- Introduced this patch.
Changes since v1:
- N/A
---
arch/x86/include/asm/smp.h | 3 +++
arch/x86/kernel/acpi/madt_wakeup.c | 20 +++++++++++++++-----
2 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 22bfebe6776d..47ac4381a805 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -149,6 +149,9 @@ static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
return per_cpu(cpu_l2c_shared_map, cpu);
}
+void acpi_setup_mp_wakeup_mailbox(u64 addr);
+struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void);
+
#else /* !CONFIG_SMP */
#define wbinvd_on_cpu(cpu) wbinvd()
static inline void wbinvd_on_all_cpus(void)
diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
index 6d7603511f52..c3ac5ecf3e7d 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -37,6 +37,7 @@ static void acpi_mp_play_dead(void)
static void acpi_mp_cpu_die(unsigned int cpu)
{
+ struct acpi_madt_multiproc_wakeup_mailbox *mailbox = acpi_get_mp_wakeup_mailbox();
u32 apicid = per_cpu(x86_cpu_to_apicid, cpu);
unsigned long timeout;
@@ -46,13 +47,13 @@ static void acpi_mp_cpu_die(unsigned int cpu)
*
* BIOS has to clear 'command' field of the mailbox.
*/
- acpi_mp_wake_mailbox->apic_id = apicid;
- smp_store_release(&acpi_mp_wake_mailbox->command,
+ mailbox->apic_id = apicid;
+ smp_store_release(&mailbox->command,
ACPI_MP_WAKE_COMMAND_TEST);
/* Don't wait longer than a second. */
timeout = USEC_PER_SEC;
- while (READ_ONCE(acpi_mp_wake_mailbox->command) && --timeout)
+ while (READ_ONCE(mailbox->command) && --timeout)
udelay(1);
if (!timeout)
@@ -227,7 +228,7 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
acpi_table_print_madt_entry(&header->common);
- acpi_mp_wake_mailbox_paddr = mp_wake->mailbox_address;
+ acpi_setup_mp_wakeup_mailbox(mp_wake->mailbox_address);
if (mp_wake->version >= ACPI_MADT_MP_WAKEUP_VERSION_V1 &&
mp_wake->header.length >= ACPI_MADT_MP_WAKEUP_SIZE_V1) {
@@ -243,7 +244,16 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
acpi_mp_disable_offlining(mp_wake);
}
+ return 0;
+}
+
+void __init acpi_setup_mp_wakeup_mailbox(u64 mailbox_paddr)
+{
+ acpi_mp_wake_mailbox_paddr = mailbox_paddr;
apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
+}
- return 0;
+struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
+{
+ return acpi_mp_wake_mailbox;
}
--
2.43.0
^ permalink raw reply related
* [PATCH v6 02/10] x86/acpi: Move acpi_wakeup_cpu() and helpers to smpwakeup.c
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri,
Rafael J. Wysocki, Yunhong Jiang, Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
The bootstrap processor uses acpi_wakeup_cpu() to indicate to firmware that
it wants to boot a secondary CPU using a mailbox as described in the
Multiprocessor Wakeup Structure of the ACPI specification.
The platform firmware may implement the mailbox as described in the ACPI
specification but enumerate it using a DeviceTree graph. An example of
this is the OpenHCL paravisor.
Move the code used to setup and use the mailbox for CPU wakeup out of the
ACPI directory into a new smpwakeup.c file that can be used by both ACPI
and DeviceTree.
No functional changes are intended.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Co-developed-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Minor change to the changelog. (Rafael)
- Added Acked-by tag from Rafael. Thanks!
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- Removed dependency on CONFIG_OF. It will be added in a later patch.
(Rafael)
- Rebased on v6.16-rc3.
Changes since v3:
- Create a new file smpwakeup.c instead of relocating it to smpboot.c.
(Rafael)
Changes since v2:
- Only move to smpboot.c the portions of the code that configure and
use the mailbox. This also resolved the compile warnings about unused
functions that Michael Kelley reported.
- Edited the commit message for clarity.
Changes since v1:
- None.
---
arch/x86/Kconfig | 7 ++++
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/acpi/madt_wakeup.c | 76 ----------------------------------
arch/x86/kernel/smpwakeup.c | 83 ++++++++++++++++++++++++++++++++++++++
4 files changed, 91 insertions(+), 76 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index fa3b616af03a..f57192a34a87 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1108,6 +1108,13 @@ config X86_LOCAL_APIC
depends on X86_64 || SMP || X86_UP_APIC || PCI_MSI
select IRQ_DOMAIN_HIERARCHY
+config X86_MAILBOX_WAKEUP
+ def_bool y
+ depends on ACPI_MADT_WAKEUP
+ depends on X86_64
+ depends on SMP
+ depends on X86_LOCAL_APIC
+
config ACPI_MADT_WAKEUP
def_bool y
depends on X86_64
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index bc184dd38d99..a9a1fbc798fb 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -94,6 +94,7 @@ apm-y := apm_32.o
obj-$(CONFIG_APM) += apm.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_SMP) += smpboot.o
+obj-$(CONFIG_X86_MAILBOX_WAKEUP) += smpwakeup.o
obj-$(CONFIG_X86_TSC) += tsc_sync.o
obj-$(CONFIG_SMP) += setup_percpu.o
obj-$(CONFIG_X86_MPPARSE) += mpparse.o
diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
index c3ac5ecf3e7d..a7e0158269b0 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -2,12 +2,10 @@
#include <linux/acpi.h>
#include <linux/cpu.h>
#include <linux/delay.h>
-#include <linux/io.h>
#include <linux/kexec.h>
#include <linux/memblock.h>
#include <linux/pgtable.h>
#include <linux/sched/hotplug.h>
-#include <asm/apic.h>
#include <asm/barrier.h>
#include <asm/init.h>
#include <asm/intel_pt.h>
@@ -15,12 +13,6 @@
#include <asm/processor.h>
#include <asm/reboot.h>
-/* Physical address of the Multiprocessor Wakeup Structure mailbox */
-static u64 acpi_mp_wake_mailbox_paddr __ro_after_init;
-
-/* Virtual address of the Multiprocessor Wakeup Structure mailbox */
-static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox;
-
static u64 acpi_mp_pgd __ro_after_init;
static u64 acpi_mp_reset_vector_paddr __ro_after_init;
@@ -127,63 +119,6 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
return 0;
}
-static int acpi_wakeup_cpu(u32 apicid, unsigned long start_ip, unsigned int cpu)
-{
- if (!acpi_mp_wake_mailbox_paddr) {
- pr_warn_once("No MADT mailbox: cannot bringup secondary CPUs. Booting with kexec?\n");
- return -EOPNOTSUPP;
- }
-
- /*
- * Remap mailbox memory only for the first call to acpi_wakeup_cpu().
- *
- * Wakeup of secondary CPUs is fully serialized in the core code.
- * No need to protect acpi_mp_wake_mailbox from concurrent accesses.
- */
- if (!acpi_mp_wake_mailbox) {
- acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr,
- sizeof(*acpi_mp_wake_mailbox),
- MEMREMAP_WB);
- }
-
- /*
- * Mailbox memory is shared between the firmware and OS. Firmware will
- * listen on mailbox command address, and once it receives the wakeup
- * command, the CPU associated with the given apicid will be booted.
- *
- * The value of 'apic_id' and 'wakeup_vector' must be visible to the
- * firmware before the wakeup command is visible. smp_store_release()
- * ensures ordering and visibility.
- */
- acpi_mp_wake_mailbox->apic_id = apicid;
- acpi_mp_wake_mailbox->wakeup_vector = start_ip;
- smp_store_release(&acpi_mp_wake_mailbox->command,
- ACPI_MP_WAKE_COMMAND_WAKEUP);
-
- /*
- * Wait for the CPU to wake up.
- *
- * The CPU being woken up is essentially in a spin loop waiting to be
- * woken up. It should not take long for it wake up and acknowledge by
- * zeroing out ->command.
- *
- * ACPI specification doesn't provide any guidance on how long kernel
- * has to wait for a wake up acknowledgment. It also doesn't provide
- * a way to cancel a wake up request if it takes too long.
- *
- * In TDX environment, the VMM has control over how long it takes to
- * wake up secondary. It can postpone scheduling secondary vCPU
- * indefinitely. Giving up on wake up request and reporting error opens
- * possible attack vector for VMM: it can wake up a secondary CPU when
- * kernel doesn't expect it. Wait until positive result of the wake up
- * request.
- */
- while (READ_ONCE(acpi_mp_wake_mailbox->command))
- cpu_relax();
-
- return 0;
-}
-
static void acpi_mp_disable_offlining(struct acpi_madt_multiproc_wakeup *mp_wake)
{
cpu_hotplug_disable_offlining();
@@ -246,14 +181,3 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
return 0;
}
-
-void __init acpi_setup_mp_wakeup_mailbox(u64 mailbox_paddr)
-{
- acpi_mp_wake_mailbox_paddr = mailbox_paddr;
- apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
-}
-
-struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
-{
- return acpi_mp_wake_mailbox;
-}
diff --git a/arch/x86/kernel/smpwakeup.c b/arch/x86/kernel/smpwakeup.c
new file mode 100644
index 000000000000..5089bcda615d
--- /dev/null
+++ b/arch/x86/kernel/smpwakeup.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/acpi.h>
+#include <linux/io.h>
+#include <linux/printk.h>
+#include <linux/types.h>
+#include <asm/apic.h>
+#include <asm/barrier.h>
+#include <asm/processor.h>
+
+/* Physical address of the Multiprocessor Wakeup Structure mailbox */
+static u64 acpi_mp_wake_mailbox_paddr __ro_after_init;
+
+/* Virtual address of the Multiprocessor Wakeup Structure mailbox */
+static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox;
+
+static int acpi_wakeup_cpu(u32 apicid, unsigned long start_ip, unsigned int cpu)
+{
+ if (!acpi_mp_wake_mailbox_paddr) {
+ pr_warn_once("No MADT mailbox: cannot bringup secondary CPUs. Booting with kexec?\n");
+ return -EOPNOTSUPP;
+ }
+
+ /*
+ * Remap mailbox memory only for the first call to acpi_wakeup_cpu().
+ *
+ * Wakeup of secondary CPUs is fully serialized in the core code.
+ * No need to protect acpi_mp_wake_mailbox from concurrent accesses.
+ */
+ if (!acpi_mp_wake_mailbox) {
+ acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr,
+ sizeof(*acpi_mp_wake_mailbox),
+ MEMREMAP_WB);
+ }
+
+ /*
+ * Mailbox memory is shared between the firmware and OS. Firmware will
+ * listen on mailbox command address, and once it receives the wakeup
+ * command, the CPU associated with the given apicid will be booted.
+ *
+ * The value of 'apic_id' and 'wakeup_vector' must be visible to the
+ * firmware before the wakeup command is visible. smp_store_release()
+ * ensures ordering and visibility.
+ */
+ acpi_mp_wake_mailbox->apic_id = apicid;
+ acpi_mp_wake_mailbox->wakeup_vector = start_ip;
+ smp_store_release(&acpi_mp_wake_mailbox->command,
+ ACPI_MP_WAKE_COMMAND_WAKEUP);
+
+ /*
+ * Wait for the CPU to wake up.
+ *
+ * The CPU being woken up is essentially in a spin loop waiting to be
+ * woken up. It should not take long for it wake up and acknowledge by
+ * zeroing out ->command.
+ *
+ * ACPI specification doesn't provide any guidance on how long kernel
+ * has to wait for a wake up acknowledgment. It also doesn't provide
+ * a way to cancel a wake up request if it takes too long.
+ *
+ * In TDX environment, the VMM has control over how long it takes to
+ * wake up secondary. It can postpone scheduling secondary vCPU
+ * indefinitely. Giving up on wake up request and reporting error opens
+ * possible attack vector for VMM: it can wake up a secondary CPU when
+ * kernel doesn't expect it. Wait until positive result of the wake up
+ * request.
+ */
+ while (READ_ONCE(acpi_mp_wake_mailbox->command))
+ cpu_relax();
+
+ return 0;
+}
+
+void __init acpi_setup_mp_wakeup_mailbox(u64 mailbox_paddr)
+{
+ acpi_mp_wake_mailbox_paddr = mailbox_paddr;
+ apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
+}
+
+struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
+{
+ return acpi_mp_wake_mailbox;
+}
--
2.43.0
^ permalink raw reply related
* [PATCH v6 03/10] dt-bindings: reserved-memory: Wakeup Mailbox for Intel processors
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri,
Rafael J. Wysocki, Yunhong Jiang, Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
Add DeviceTree bindings to enumerate the wakeup mailbox used in platform
firmware for Intel processors.
x86 platforms commonly boot secondary CPUs using an INIT assert, de-assert
followed by Start-Up IPI messages. The wakeup mailbox can be used when this
mechanism is unavailable.
The wakeup mailbox offers more control to the operating system to boot
secondary CPUs than a spin-table. It allows the reuse of the same wakeup
vector for all CPUs while maintaining control over which CPUs to boot and
when. While it is possible to achieve the same level of control using a
spin-table, it would require specifying a separate `cpu-release-addr` for
each secondary CPU.
The operation and structure of the mailbox are described in the
Multiprocessor Wakeup Structure defined in the ACPI specification. Note
that this structure does not specify how to publish the mailbox to the
operating system (ACPI-based platform firmware uses a separate table). No
ACPI table is needed in DeviceTree-based firmware to enumerate the mailbox.
Nodes that want to refer to the reserved memory usually define
a `memory-region` property. /cpus/cpu* nodes would want to refer to the
mailbox, but they do not have such property defined in the DeviceTree
specification. Moreover, it would imply that there is a memory region per
CPU. Instead, add a `compatible` property that the operating system can use
to discover the mailbox.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Co-developed-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Reworded the changelog for clarity.
- Added Acked-by tag from Rafael. Thanks!
- Added Reviewed-by tag from Rob. Thanks!
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- Specified the version and section of the ACPI spec in which the
wakeup mailbox is defined. (Rafael)
- Fixed a warning from yamllint about line lengths of URLs.
Changes since v3:
- Removed redefinitions of the mailbox and instead referred to ACPI
specification as per discussion on LKML.
- Clarified that DeviceTree-based firmware do not require the use of
ACPI tables to enumerate the mailbox. (Rob)
- Described the need of using a `compatible` property.
- Dropped the `alignment` property. (Krzysztof, Rafael)
- Used a real address for the mailbox node. (Krzysztof)
Changes since v2:
- Implemented the mailbox as a reserved-memory node. Add to it a
`compatible` property. (Krzysztof)
- Explained the relationship between the mailbox and the `enable-mehod`
property of the CPU nodes.
- Expanded the documentation of the binding.
Changes since v1:
- Added more details to the description of the binding.
- Added requirement a new requirement for cpu@N nodes to add an
`enable-method`.
---
.../reserved-memory/intel,wakeup-mailbox.yaml | 50 ++++++++++++++++++++++
1 file changed, 50 insertions(+)
diff --git a/Documentation/devicetree/bindings/reserved-memory/intel,wakeup-mailbox.yaml b/Documentation/devicetree/bindings/reserved-memory/intel,wakeup-mailbox.yaml
new file mode 100644
index 000000000000..a80d3bac44c2
--- /dev/null
+++ b/Documentation/devicetree/bindings/reserved-memory/intel,wakeup-mailbox.yaml
@@ -0,0 +1,50 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/reserved-memory/intel,wakeup-mailbox.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Wakeup Mailbox for Intel processors
+
+description: |
+ The Wakeup Mailbox provides a mechanism for the operating system to wake up
+ secondary CPUs on Intel processors. It is an alternative to the INIT-!INIT-
+ SIPI sequence used on most x86 systems.
+
+ The structure and operation of the mailbox is described in the Multiprocessor
+ Wakeup Structure of the ACPI specification version 6.6 section 5.2.12.19 [1].
+
+ The implementation of the mailbox in platform firmware is described in the
+ Intel TDX Virtual Firmware Design Guide section 4.3.5 [2].
+
+ 1: https://uefi.org/specs/ACPI/6.6/05_ACPI_Software_Programming_Model.html#multiprocessor-wakeup-structure
+ 2: https://www.intel.com/content/www/us/en/content-details/733585/intel-tdx-virtual-firmware-design-guide.html
+
+
+maintainers:
+ - Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
+
+allOf:
+ - $ref: reserved-memory.yaml
+
+properties:
+ compatible:
+ const: intel,wakeup-mailbox
+
+required:
+ - compatible
+ - reg
+
+unevaluatedProperties: false
+
+examples:
+ - |
+ reserved-memory {
+ #address-cells = <2>;
+ #size-cells = <1>;
+
+ wakeup-mailbox@ffff0000 {
+ compatible = "intel,wakeup-mailbox";
+ reg = <0x0 0xffff0000 0x1000>;
+ };
+ };
--
2.43.0
^ permalink raw reply related
* [PATCH v6 04/10] x86/dt: Parse the Wakeup Mailbox for Intel processors
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri, Yunhong Jiang,
Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
The Wakeup Mailbox is a mechanism to boot secondary CPUs on systems that do
not want or cannot use the INIT + StartUp IPI messages.
The platform firmware is expected to implement the mailbox as described in
the Multiprocessor Wakeup Structure of the ACPI specification. It is also
expected to publish the mailbox to the operating system as described in the
corresponding DeviceTree schema that accompanies the documentation of the
Linux kernel.
Reuse the existing functionality to set the memory location of the mailbox
and update the wakeup_secondary_cpu_64() APIC callback. Make this
functionality available to DeviceTree-based systems by making CONFIG_X86_
MAILBOX_WAKEUP depend on either CONFIG_OF or CONFIG_ACPI_MADT_WAKEUP.
do_boot_cpu() uses wakeup_secondary_cpu_64() when set. It will be set if a
wakeup mailbox is enumerated via an ACPI table or a DeviceTree node. For
cases in which this behavior is not desired, this APIC callback can be
updated later during boot using platform-specific hooks.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Co-developed-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- Made CONFIG_X86_MAILBOX_WAKEUP depend on CONFIG_OF or CONFIG_ACPI_
MADT_WAKEUP.
Changes since v3:
- Look for the wakeup mailbox unconditionally, regardless of whether
cpu@N nodes have an `enable-method` property.
- Add a reference to the ACPI specification. (Rafael)
Changes since v2:
- Added extra sanity checks when parsing the mailbox node.
- Probe the mailbox using its `compatible` property
- Setup the Wakeup Mailbox if the `enable-method` is found in the CPU
nodes.
- Cleaned up unneeded ifdeffery.
- Clarified the mechanisms used to override the wakeup_secondary_64()
callback to not use the mailbox when not desired. (Michael)
- Edited the commit message for clarity.
Changes since v1:
- Disabled CPU offlining.
- Modified dtb_parse_mp_wake() to return the address of the mailbox.
---
arch/x86/Kconfig | 2 +-
arch/x86/kernel/devicetree.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 48 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f57192a34a87..5a9d0b2d5174 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1110,7 +1110,7 @@ config X86_LOCAL_APIC
config X86_MAILBOX_WAKEUP
def_bool y
- depends on ACPI_MADT_WAKEUP
+ depends on OF || ACPI_MADT_WAKEUP
depends on X86_64
depends on SMP
depends on X86_LOCAL_APIC
diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
index dd8748c45529..494a560614a8 100644
--- a/arch/x86/kernel/devicetree.c
+++ b/arch/x86/kernel/devicetree.c
@@ -17,6 +17,7 @@
#include <linux/pci.h>
#include <linux/of_pci.h>
#include <linux/initrd.h>
+#include <linux/smp.h>
#include <asm/irqdomain.h>
#include <asm/hpet.h>
@@ -125,6 +126,51 @@ static void __init dtb_setup_hpet(void)
#endif
}
+#if defined(CONFIG_X86_64) && defined(CONFIG_SMP)
+
+#define WAKEUP_MAILBOX_SIZE 0x1000
+#define WAKEUP_MAILBOX_ALIGN 0x1000
+
+/** dtb_wakeup_mailbox_setup() - Parse the wakeup mailbox from the device tree
+ *
+ * Look for the presence of a wakeup mailbox in the DeviceTree. The mailbox is
+ * expected to follow the structure and operation described in the Multiprocessor
+ * Wakeup Structure of the ACPI specification.
+ */
+static void __init dtb_wakeup_mailbox_setup(void)
+{
+ struct device_node *node;
+ struct resource res;
+
+ node = of_find_compatible_node(NULL, NULL, "intel,wakeup-mailbox");
+ if (!node)
+ return;
+
+ if (of_address_to_resource(node, 0, &res))
+ goto done;
+
+ /* The mailbox is a 4KB-aligned region.*/
+ if (res.start & (WAKEUP_MAILBOX_ALIGN - 1))
+ goto done;
+
+ /* The mailbox has a size of 4KB. */
+ if (res.end - res.start + 1 != WAKEUP_MAILBOX_SIZE)
+ goto done;
+
+ /* Not supported when the mailbox is used. */
+ cpu_hotplug_disable_offlining();
+
+ acpi_setup_mp_wakeup_mailbox(res.start);
+done:
+ of_node_put(node);
+}
+#else /* !CONFIG_X86_64 || !CONFIG_SMP */
+static inline int dtb_wakeup_mailbox_setup(void)
+{
+ return -EOPNOTSUPP;
+}
+#endif /* CONFIG_X86_64 && CONFIG_SMP */
+
#ifdef CONFIG_X86_LOCAL_APIC
static void __init dtb_cpu_setup(void)
@@ -287,6 +333,7 @@ static void __init x86_dtb_parse_smp_config(void)
dtb_setup_hpet();
dtb_apic_setup();
+ dtb_wakeup_mailbox_setup();
}
void __init x86_flattree_get_config(void)
--
2.43.0
^ permalink raw reply related
* [PATCH v6 05/10] x86/hyperv/vtl: Set real_mode_header in hv_vtl_init_platform()
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri, Yunhong Jiang,
Thomas Gleixner, Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
From: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Hyper-V VTL clears x86_platform.realmode_{init(), reserve()} in
hv_vtl_init_platform() whereas it sets real_mode_header later in
hv_vtl_early_init(). There is no need to deal with the settings of real
mode memory in two places. Also, both functions are called much earlier
than x86_platform.realmode_init() (via an early_initcall), where the
real_mode_header is needed.
Set real_mode_header in hv_vtl_init_platform() to keep all code dealing
with memory for the real mode trampoline in one place. Besides making the
code more readable, it prepares it for a subsequent changeset in which the
behavior needs to change to support Hyper-V VTL guests in TDX a
environment.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Corrected reference to hv_vtl_init_platform() in the changelog.
(Dexuan)
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- None
Changes since v3:
- Added Reviewed-by tag from Michael. Thanks!
Changes since v2:
- Edited the commit message for clarity.
Changes since v1:
- Introduced this patch.
---
arch/x86/hyperv/hv_vtl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 042e8712d8de..e10b63b7a49f 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -65,6 +65,7 @@ void __init hv_vtl_init_platform(void)
x86_platform.realmode_reserve = x86_init_noop;
x86_platform.realmode_init = x86_init_noop;
+ real_mode_header = &hv_vtl_real_mode_header;
x86_init.irqs.pre_vector_init = x86_init_noop;
x86_init.timers.timer_init = x86_init_noop;
x86_init.resources.probe_roms = x86_init_noop;
@@ -244,7 +245,6 @@ int __init hv_vtl_early_init(void)
panic("XSAVE has to be disabled as it is not supported by this module.\n"
"Please add 'noxsave' to the kernel command line.\n");
- real_mode_header = &hv_vtl_real_mode_header;
apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
return 0;
--
2.43.0
^ permalink raw reply related
* [PATCH v6 06/10] x86/realmode: Make the location of the trampoline configurable
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri, Yunhong Jiang,
Thomas Gleixner, Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
From: Yunhong Jiang <yunhong.jiang@linux.intel.com>
x86 CPUs boot in real mode. This mode uses a 1MB address space. The
trampoline must reside below this 1MB memory boundary.
There are platforms in which the firmware boots the secondary CPUs,
switches them to long mode and transfers control to the kernel. An example
of such a mechanism is the ACPI Multiprocessor Wakeup Structure.
In this scenario there is no restriction on locating the trampoline under
1MB memory. Moreover, certain platforms (for example, Hyper-V VTL guests)
may not have memory available for allocation below 1MB.
Add a new member to struct x86_init_resources to specify the upper bound
for the location of the trampoline memory. Preserve the default upper bound
of 1MB to conserve the current behavior.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- None
Changes since v3:
- Added Reviewed-by tag from Michael. Thanks!
Changes since v2:
- Edited the commit message for clarity.
- Minor tweaks to comments.
- Removed the option to not reserve the first 1MB of memory as it is
not needed.
Changes since v1:
- Added this patch using code that Thomas suggested:
https://lore.kernel.org/lkml/87a5ho2q6x.ffs@tglx/
---
arch/x86/include/asm/x86_init.h | 3 +++
arch/x86/kernel/x86_init.c | 3 +++
arch/x86/realmode/init.c | 7 +++----
3 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 36698cc9fb44..e770ce507a87 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -31,12 +31,15 @@ struct x86_init_mpparse {
* platform
* @memory_setup: platform specific memory setup
* @dmi_setup: platform specific DMI setup
+ * @realmode_limit: platform specific address limit for the real mode trampoline
+ * (default 1M)
*/
struct x86_init_resources {
void (*probe_roms)(void);
void (*reserve_resources)(void);
char *(*memory_setup)(void);
void (*dmi_setup)(void);
+ unsigned long realmode_limit;
};
/**
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index 0a2bbd674a6d..a25fd7282811 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -9,6 +9,7 @@
#include <linux/export.h>
#include <linux/pci.h>
#include <linux/acpi.h>
+#include <linux/sizes.h>
#include <asm/acpi.h>
#include <asm/bios_ebda.h>
@@ -69,6 +70,8 @@ struct x86_init_ops x86_init __initdata = {
.reserve_resources = reserve_standard_io_resources,
.memory_setup = e820__memory_setup_default,
.dmi_setup = dmi_setup,
+ /* Has to be under 1M so we can execute real-mode AP code. */
+ .realmode_limit = SZ_1M,
},
.mpparse = {
diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
index 88be32026768..694d80a5c68e 100644
--- a/arch/x86/realmode/init.c
+++ b/arch/x86/realmode/init.c
@@ -46,7 +46,7 @@ void load_trampoline_pgtable(void)
void __init reserve_real_mode(void)
{
- phys_addr_t mem;
+ phys_addr_t mem, limit = x86_init.resources.realmode_limit;
size_t size = real_mode_size_needed();
if (!size)
@@ -54,10 +54,9 @@ void __init reserve_real_mode(void)
WARN_ON(slab_is_available());
- /* Has to be under 1M so we can execute real-mode AP code. */
- mem = memblock_phys_alloc_range(size, PAGE_SIZE, 0, 1<<20);
+ mem = memblock_phys_alloc_range(size, PAGE_SIZE, 0, limit);
if (!mem)
- pr_info("No sub-1M memory is available for the trampoline\n");
+ pr_info("No memory below %pa for the real-mode trampoline\n", &limit);
else
set_real_mode_mem(mem);
--
2.43.0
^ permalink raw reply related
* [PATCH v6 07/10] x86/hyperv/vtl: Setup the 64-bit trampoline for TDX guests
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri, Yunhong Jiang,
Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
From: Yunhong Jiang <yunhong.jiang@linux.intel.com>
The hypervisor is an untrusted entity for TDX guests. It cannot be used
to boot secondary CPUs - neither via hypercalls nor the INIT assert,
de-assert, plus Start-Up IPI messages.
Instead, the platform virtual firmware boots the secondary CPUs and
puts them in a state to transfer control to the kernel. This mechanism uses
the wakeup mailbox described in the Multiprocessor Wakeup Structure of the
ACPI specification. The entry point to the kernel is trampoline_start64.
Allocate and setup the trampoline using the default x86_platform callbacks.
The platform firmware configures the secondary CPUs in long mode. It is no
longer necessary to locate the trampoline under 1MB memory. After handoff
from firmware, the trampoline code switches briefly to 32-bit addressing
mode, which has an addressing limit of 4GB. Set the upper bound of the
trampoline memory accordingly.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- None
Changes since v3:
- Added Reviewed-by tag from Michael. Thanks!
Changes since v2:
- Added a note regarding there is no need to check for a present
paravisor.
- Edited commit message for clarity.
Changes since v1:
- Dropped the function hv_reserve_real_mode(). Instead, used the new
members realmode_limit and reserve_bios members of x86_init to
set the upper bound of the trampoline memory. (Thomas)
---
arch/x86/hyperv/hv_vtl.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index e10b63b7a49f..ca0d23206e67 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -63,9 +63,14 @@ void __init hv_vtl_init_platform(void)
*/
pr_info("Linux runs in Hyper-V Virtual Trust Level %d\n", ms_hyperv.vtl);
- x86_platform.realmode_reserve = x86_init_noop;
- x86_platform.realmode_init = x86_init_noop;
- real_mode_header = &hv_vtl_real_mode_header;
+ /* There is no paravisor present if we are here. */
+ if (hv_isolation_type_tdx()) {
+ x86_init.resources.realmode_limit = SZ_4G;
+ } else {
+ x86_platform.realmode_reserve = x86_init_noop;
+ x86_platform.realmode_init = x86_init_noop;
+ real_mode_header = &hv_vtl_real_mode_header;
+ }
x86_init.irqs.pre_vector_init = x86_init_noop;
x86_init.timers.timer_init = x86_init_noop;
x86_init.resources.probe_roms = x86_init_noop;
--
2.43.0
^ permalink raw reply related
* [PATCH v6 08/10] x86/smpwakeup: Add a helper get the address of the wakeup mailbox
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri, Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
A Hyper-V VTL level 2 guest in a TDX environment needs to map the physical
page of the ACPI Multiprocessor Wakeup Structure as private (encrypted). It
needs to know the physical address of this structure. Add a helper function
to retrieve the address.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Suggested-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- None
Changes since v3:
- Renamed function to acpi_get_mp_wakeup_mailbox_paddr().
- Added Reviewed-by tag from Michael. Thanks!
Changes since v2:
- Introduced this patch
Changes since v1:
- N/A
---
arch/x86/include/asm/smp.h | 1 +
arch/x86/kernel/smpwakeup.c | 5 +++++
2 files changed, 6 insertions(+)
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 47ac4381a805..71de1963f984 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -151,6 +151,7 @@ static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
void acpi_setup_mp_wakeup_mailbox(u64 addr);
struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void);
+u64 acpi_get_mp_wakeup_mailbox_paddr(void);
#else /* !CONFIG_SMP */
#define wbinvd_on_cpu(cpu) wbinvd()
diff --git a/arch/x86/kernel/smpwakeup.c b/arch/x86/kernel/smpwakeup.c
index 5089bcda615d..f730a66b6fc8 100644
--- a/arch/x86/kernel/smpwakeup.c
+++ b/arch/x86/kernel/smpwakeup.c
@@ -81,3 +81,8 @@ struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
{
return acpi_mp_wake_mailbox;
}
+
+u64 acpi_get_mp_wakeup_mailbox_paddr(void)
+{
+ return acpi_mp_wake_mailbox_paddr;
+}
--
2.43.0
^ permalink raw reply related
* [PATCH v6 09/10] x86/hyperv/vtl: Mark the wakeup mailbox page as private
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri, Yunhong Jiang,
Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
From: Yunhong Jiang <yunhong.jiang@linux.intel.com>
The current code maps MMIO devices as shared (decrypted) by default in a
confidential computing VM.
In a TDX environment, secondary CPUs are booted using the Multiprocessor
Wakeup Structure defined in the ACPI specification. The virtual firmware
and the operating system function in the guest context, without
intervention from the VMM. Map the physical memory of the mailbox as
private. Use the is_private_mmio() callback.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Fixed a compile error with !CONFIG_X86_MAILBOX_WAKEUP.
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- None
Changes since v3:
- Updated to use the renamed function acpi_get_mp_wakeup_mailbox_paddr().
- Added Reviewed-by tag from Michael. Thanks!
Changes since v2:
- Use the new helper function get_mp_wakeup_mailbox_paddr().
- Edited the commit message for clarity.
Changes since v1:
- Added the helper function within_page() to improve readability
- Override the is_private_mmio() callback when detecting a TDX
environment. The address of the mailbox is checked in
hv_is_private_mmio_tdx().
---
arch/x86/hyperv/hv_vtl.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index ca0d23206e67..4a15de4d5ec2 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -54,6 +54,22 @@ static void __noreturn hv_vtl_restart(char __maybe_unused *cmd)
hv_vtl_emergency_restart();
}
+static inline bool within_page(u64 addr, u64 start)
+{
+ return addr >= start && addr < (start + PAGE_SIZE);
+}
+
+static bool hv_vtl_is_private_mmio_tdx(u64 addr)
+{
+ if (IS_ENABLED(CONFIG_X86_MAILBOX_WAKEUP)) {
+ u64 mb_addr = acpi_get_mp_wakeup_mailbox_paddr();
+
+ return mb_addr && within_page(addr, mb_addr);
+ }
+
+ return false;
+}
+
void __init hv_vtl_init_platform(void)
{
/*
@@ -66,6 +82,8 @@ void __init hv_vtl_init_platform(void)
/* There is no paravisor present if we are here. */
if (hv_isolation_type_tdx()) {
x86_init.resources.realmode_limit = SZ_4G;
+ x86_platform.hyper.is_private_mmio = hv_vtl_is_private_mmio_tdx;
+
} else {
x86_platform.realmode_reserve = x86_init_noop;
x86_platform.realmode_init = x86_init_noop;
--
2.43.0
^ permalink raw reply related
* [PATCH v6 10/10] x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs
From: Ricardo Neri @ 2025-10-17 2:57 UTC (permalink / raw)
To: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki
Cc: Saurabh Sengar, Chris Oo, Kirill A. Shutemov, linux-hyperv,
devicetree, linux-acpi, linux-kernel, Ricardo Neri, Ricardo Neri
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-0-40435fb9305e@linux.intel.com>
The hypervisor is an untrusted entity for TDX guests. It cannot be used
to boot secondary CPUs. The function hv_vtl_wakeup_secondary_cpu() cannot
be used.
Instead, the virtual firmware boots the secondary CPUs and places them in
a state to transfer control to the kernel using the wakeup mailbox. The
firmware enumerates the mailbox via either an ACPI table or a DeviceTree
node.
If the wakeup mailbox is present, the kernel updates the APIC callback
wakeup_secondary_cpu_64() to use it.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes since v4:
- None
Changes since v3:
- Added Reviewed-by tag from Michael. Thanks!
Changes since v2:
- Unconditionally use the wakeup mailbox in a TDX confidential VM.
(Michael).
- Edited the commit message for clarity.
Changes since v1:
- None
---
arch/x86/hyperv/hv_vtl.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 4a15de4d5ec2..e866e643b66c 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -268,7 +268,15 @@ int __init hv_vtl_early_init(void)
panic("XSAVE has to be disabled as it is not supported by this module.\n"
"Please add 'noxsave' to the kernel command line.\n");
- apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
+ /*
+ * TDX confidential VMs do not trust the hypervisor and cannot use it to
+ * boot secondary CPUs. Instead, they will be booted using the wakeup
+ * mailbox if detected during boot. See setup_arch().
+ *
+ * There is no paravisor present if we are here.
+ */
+ if (!hv_isolation_type_tdx())
+ apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
return 0;
}
--
2.43.0
^ permalink raw reply related
* [PATCH v9 0/2] Drivers: hv: Introduce new driver - mshv_vtl
From: Naman Jain @ 2025-10-17 7:45 UTC (permalink / raw)
To: K . Y . Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen,
H . Peter Anvin
Cc: linux-hyperv, linux-kernel, x86, Mukesh Rathor,
Stanislav Kinsburskii, Naman Jain, Nuno Das Neves, Peter Zijlstra,
Sean Christopherson, Paolo Bonzini, Michael Kelley,
Christoph Hellwig, Saurabh Sengar, ALOK TIWARI
Introduce a new mshv_vtl driver to provide an interface for Virtual
Machine Monitor like OpenVMM and its use as OpenHCL paravisor to
control VTL0 (Virtual trust Level).
Expose devices and support IOCTLs for features like VTL creation,
VTL0 memory management, context switch, making hypercalls,
mapping VTL0 address space to VTL2 userspace, getting new VMBus
messages and channel events in VTL2 etc.
OpenVMM : https://openvmm.dev/guide/
Changes since v8:
https://lore.kernel.org/all/20251013060353.67326-1-namjain@linux.microsoft.com/
Addressed Sean's comments:
* Removed forcing SIGPENDING, and other minor changes, in
mshv_vtl_ioctl_return_to_lower_vtl after referring
to Sean's earlier changes for xfer_to_guest_mode_handle_work.
* Rebased and resolved merge conflicts, compilation errors on latest
linux-next kernel tip, after Roman's Confidential VM changes,
which merged recently. No functional changes.
https://lore.kernel.org/all/20251008233419.20372-1-romank@linux.microsoft.com/
Changes since v7:
https://lore.kernel.org/all/20250729051436.190703-1-namjain@linux.microsoft.com/
Addressed Peter's concerns. Thanks Peter, Paolo, Sean for valuable inputs.
Discussion- https://lore.kernel.org/all/20250825055208.238729-1-namjain@linux.microsoft.com/
* moved assembly code to arch/x86/
* This prevents the need to export hv_hypercall_pg
* Will make it easier to add support for other architectures in the future
* moved assembly code to a separate .S file (arch/x86/hyperv/mshv_vtl_asm.S)
* Used noinstr for this new function in .S file
* Fixed save/restore logic of callee registers, rbp to fix previous objtool warning
* used static call instead of indirect call
* used asm offsets similar to KVM code in assembly file (arch/x86/hyperv/mshv-asm-offsets.c)
* Removed the usage of STACK_FRAME_NON_STANDARD.
Other changes-
* Changed logic to use xfer_to_guest_mode_handle_work and VIRT_XFER_TO_GUEST_WORK
after recently merged changes.
* Removed Reviewed-by Tags after recent changes.
Changes since v6:
https://lore.kernel.org/all/20250724082547.195235-1-namjain@linux.microsoft.com/
Addressed Michael's comments:
* Corrected MAX_BITMAP_SIZE size - finally
* Added missing __packed to hv_synic_overlay_page_msr
* Fixed typo in comment, added CPU hotplug info in comments
* Reverted to mutex_lock/unlock in mshv_vtl_ioctl_set_poll_file
* Unified mshv_vtl_set_reg and mshv_vtl_get_reg
* Dynamic to static allocation of reg in mshv_vtl_ioctl_(get|set)_regs
* Fixed error handling in mshv_vtl_sint_ioctl_signal_event()
Changes since v5:
https://lore.kernel.org/all/20250611072704.83199-1-namjain@linux.microsoft.com/
Addressed Michael Kelley's suggestions:
* Added "depends on HYPERV_VTL_MODE", removed "depends on HYPERV" in Kconfig
* Removed unused macro MAX_GUEST_MEM_SIZE
* Made macro dependency explicit: MSHV_PG_OFF_CPU_MASK and MSHV_REAL_OFF_SHIFT
* Refactored and corrected how allow_bitmap is used and defined. Removed PAGE_SIZE dependency.
* Added __packed for structure definitions wherever it was missing.
* Moved hv_register_vsm_* union definitions to hvgdk_mini.h, kept mshv_synic_overlay_page_msr
in the driver, renamed it and added a comment. (Nuno)
* Introduced global variables input_vtl_zero and input_vtl_normal and used them everywhere these
were defined locally
* s/"page_to_phys(reg_page) >> HV_HYP_PAGE_SHIFT"/"page_to_hvpfn(reg_page)" in
mshv_vtl_configure_reg_page
* Refactored mshv_vtl_vmbus_isr() to reduce complexity in finding and resetting bits similar to
how vmbus_chan_sched is implemented.
* Used __get_free_page() instead in mshv_vtl_alloc_context()
* Added fallback hv_setup_vmbus_handler(vmbus_isr) in hv_vtl_setup_synic() and in
hv_vtl_remove_synic().
* Maintained symmetry of functions in hv_vtl_remove_synic
* Added a note for explanation of excluding last PFN in the range provided in
mshv_vtl_ioctl_add_vtl0_mem()
* Added comments for hotplug being not supported, wherever cpu_online() was used to check if CPU
is online or not.
* Added a check for input.cpu to make sure it's less than nr_cpu_ids in
mshv_vtl_ioctl_set_poll_file()
* Removed switch-case and implemented static tables in mshv_vtl_(get|set)_reg for reducing LOC
* Simplified mshv_vtl_ioctl_(get|set)_regs to process one register at a time, and fixed earlier
bug with array of registers processing.
* Used hv_result_to_errno() in mshv_vtl_sint_ioctl_signal_event()
* Added a READ_ONCE() while reading old_eventfd in mshv_vtl_sint_ioctl_set_eventfd()
* Renamed mshv_vtl_hvcall and mshv_vtl_hvcall_setup to remove ambiguity
* Took care of latest mm patches regarding PFN_DEV, pfn_t deprecation
* Few other minor changes while reorganizing code.
Addressed Markus Elfring's suggestions:
* Used guard(mutex) for better mutex handling.
Changes since v4:
https://lore.kernel.org/all/20250610052435.1660967-1-namjain@linux.microsoft.com/
* Fixed warnings from kernel test robot for missing export.h when the
kernel is compiled with W=1 option.
Some recent changes in kernel flags these warnings and that's why it
was not seen in previous runs. Warnings in other Hyper-V drivers
will be fixed separately.
* No functional changes
Changes since v3:
https://lore.kernel.org/all/20250519045642.50609-1-namjain@linux.microsoft.com/
Addressed Stanislav's, Nuno's comments.
* Change data types for different variables, excluding the ones in uapi headers
* Added comment for the need of HUGEPAGES config in Kconfig.
* generalized new IOCTL names by removing VTL in their name.
* Rebased and added Saurabh's Reviewed-by tag
Changes since v2:
https://lore.kernel.org/all/20250512140432.2387503-1-namjain@linux.microsoft.com/
* Removed CONFIG_OF dependency (addressed Saurabh's comments)
* Fixed typo in "allow_map_intialized" variable name
Changes since v1:
https://lore.kernel.org/all/20250506084937.624680-1-namjain@linux.microsoft.com/
Addressed Saurabh's comments:
* Split the patch in 2 to keep export symbols separate
* Make MSHV_VTL module tristate and fixed compilation warning that would come when HYPERV is
compiled as a module.
* Remove the use of ref_count
* Split functionality of mshv_vtl_ioctl_get_set_regs to different functions
mshv_vtl_ioctl_(get|set)_regs as it actually make things simpler
* Fixed use of copy_from_user in atomic context in mshv_vtl_hvcall_call.
Added ToDo comment for info.
* Added extra code to free memory for vtl in error scenarios in mshv_ioctl_create_vtl()
Addressed Alok's comments regarding:
* Additional conditional checks
* corrected typo in HV_X64_REGISTER_MSR_MTRR_PHYS_MASKB case
* empty lines before return statement
* Added/edited comments, variable names, structure field names as suggested to improve
documentation - no functional change here.
Naman Jain (2):
Drivers: hv: Export some symbols for mshv_vtl
Drivers: hv: Introduce mshv_vtl driver
arch/x86/hyperv/Makefile | 10 +-
arch/x86/hyperv/hv_vtl.c | 37 +
arch/x86/hyperv/mshv-asm-offsets.c | 37 +
arch/x86/hyperv/mshv_vtl_asm.S | 95 ++
arch/x86/include/asm/mshyperv.h | 32 +
drivers/hv/Kconfig | 26 +-
drivers/hv/Makefile | 7 +-
drivers/hv/hv.c | 3 +
drivers/hv/hyperv_vmbus.h | 1 +
drivers/hv/mshv_vtl.h | 25 +
drivers/hv/mshv_vtl_main.c | 1392 ++++++++++++++++++++++++++++
drivers/hv/vmbus_drv.c | 4 +-
include/hyperv/hvgdk_mini.h | 106 +++
include/uapi/linux/mshv.h | 80 ++
14 files changed, 1851 insertions(+), 4 deletions(-)
create mode 100644 arch/x86/hyperv/mshv-asm-offsets.c
create mode 100644 arch/x86/hyperv/mshv_vtl_asm.S
create mode 100644 drivers/hv/mshv_vtl.h
create mode 100644 drivers/hv/mshv_vtl_main.c
base-commit: 1fdbb3ff1233e204e26f9f6821ae9c125a055229
--
2.43.0
^ permalink raw reply
* [PATCH v9 1/2] Drivers: hv: Export some symbols for mshv_vtl
From: Naman Jain @ 2025-10-17 7:45 UTC (permalink / raw)
To: K . Y . Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen,
H . Peter Anvin
Cc: linux-hyperv, linux-kernel, x86, Mukesh Rathor,
Stanislav Kinsburskii, Naman Jain, Nuno Das Neves, Peter Zijlstra,
Sean Christopherson, Paolo Bonzini, Michael Kelley,
Christoph Hellwig, Saurabh Sengar, ALOK TIWARI
In-Reply-To: <20251017074507.142704-1-namjain@linux.microsoft.com>
MSHV_VTL driver is going to be introduced, which is supposed to
provide interface for Virtual Machine Monitors (VMMs) to control
Virtual Trust Level (VTL). Export the symbols needed
to make it work (vmbus_isr, hv_context and hv_post_message).
Co-developed-by: Roman Kisel <romank@linux.microsoft.com>
Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Co-developed-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506110544.q0NDMQVc-lkp@intel.com/
Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
---
drivers/hv/hv.c | 3 +++
drivers/hv/hyperv_vmbus.h | 1 +
drivers/hv/vmbus_drv.c | 4 +++-
3 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 936c5f310df6..c924e3294b8b 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -18,6 +18,7 @@
#include <linux/clockchips.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
+#include <linux/export.h>
#include <clocksource/hyperv_timer.h>
#include <asm/mshyperv.h>
#include <linux/set_memory.h>
@@ -25,6 +26,7 @@
/* The one and only */
struct hv_context hv_context;
+EXPORT_SYMBOL_GPL(hv_context);
/*
* hv_init - Main initialization routine.
@@ -104,6 +106,7 @@ int hv_post_message(union hv_connection_id connection_id,
return hv_result(status);
}
+EXPORT_SYMBOL_GPL(hv_post_message);
static int hv_alloc_page(void **page, bool decrypt, const char *note)
{
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index f7fc2630c054..b2862e0a317a 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -33,6 +33,7 @@
*/
#define HV_UTIL_NEGO_TIMEOUT 55
+void vmbus_isr(void);
/* Definitions for the monitored notification facility */
union hv_monitor_trigger_group {
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 0dc4692b411a..c9ad17ed562d 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -36,6 +36,7 @@
#include <linux/syscore_ops.h>
#include <linux/dma-map-ops.h>
#include <linux/pci.h>
+#include <linux/export.h>
#include <clocksource/hyperv_timer.h>
#include <asm/mshyperv.h>
#include "hyperv_vmbus.h"
@@ -1349,7 +1350,7 @@ static void vmbus_message_sched(struct hv_per_cpu_context *hv_cpu, void *message
}
}
-static void vmbus_isr(void)
+void vmbus_isr(void)
{
struct hv_per_cpu_context *hv_cpu
= this_cpu_ptr(hv_context.cpu_context);
@@ -1362,6 +1363,7 @@ static void vmbus_isr(void)
add_interrupt_randomness(vmbus_interrupt);
}
+EXPORT_SYMBOL_GPL(vmbus_isr);
static irqreturn_t vmbus_percpu_isr(int irq, void *dev_id)
{
--
2.43.0
^ permalink raw reply related
* [PATCH v9 2/2] Drivers: hv: Introduce mshv_vtl driver
From: Naman Jain @ 2025-10-17 7:45 UTC (permalink / raw)
To: K . Y . Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen,
H . Peter Anvin
Cc: linux-hyperv, linux-kernel, x86, Mukesh Rathor,
Stanislav Kinsburskii, Naman Jain, Nuno Das Neves, Peter Zijlstra,
Sean Christopherson, Paolo Bonzini, Michael Kelley,
Christoph Hellwig, Saurabh Sengar, ALOK TIWARI
In-Reply-To: <20251017074507.142704-1-namjain@linux.microsoft.com>
Provide an interface for Virtual Machine Monitor like OpenVMM and its
use as OpenHCL paravisor to control VTL0 (Virtual trust Level).
Expose devices and support IOCTLs for features like VTL creation,
VTL0 memory management, context switch, making hypercalls,
mapping VTL0 address space to VTL2 userspace, getting new VMBus
messages and channel events in VTL2 etc.
Co-developed-by: Roman Kisel <romank@linux.microsoft.com>
Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Co-developed-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
---
arch/x86/hyperv/Makefile | 10 +-
arch/x86/hyperv/hv_vtl.c | 37 +
arch/x86/hyperv/mshv-asm-offsets.c | 37 +
arch/x86/hyperv/mshv_vtl_asm.S | 95 ++
arch/x86/include/asm/mshyperv.h | 32 +
drivers/hv/Kconfig | 26 +-
drivers/hv/Makefile | 7 +-
drivers/hv/mshv_vtl.h | 25 +
drivers/hv/mshv_vtl_main.c | 1392 ++++++++++++++++++++++++++++
include/hyperv/hvgdk_mini.h | 106 +++
include/uapi/linux/mshv.h | 80 ++
11 files changed, 1844 insertions(+), 3 deletions(-)
create mode 100644 arch/x86/hyperv/mshv-asm-offsets.c
create mode 100644 arch/x86/hyperv/mshv_vtl_asm.S
create mode 100644 drivers/hv/mshv_vtl.h
create mode 100644 drivers/hv/mshv_vtl_main.c
diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile
index d55f494f471d..aff2303c40e3 100644
--- a/arch/x86/hyperv/Makefile
+++ b/arch/x86/hyperv/Makefile
@@ -1,8 +1,16 @@
# SPDX-License-Identifier: GPL-2.0-only
obj-y := hv_init.o mmu.o nested.o irqdomain.o ivm.o
obj-$(CONFIG_X86_64) += hv_apic.o
-obj-$(CONFIG_HYPERV_VTL_MODE) += hv_vtl.o
+obj-$(CONFIG_HYPERV_VTL_MODE) += hv_vtl.o mshv_vtl_asm.o
+
+$(obj)/mshv_vtl_asm.o: $(obj)/mshv-asm-offsets.h
+
+$(obj)/mshv-asm-offsets.h: $(obj)/mshv-asm-offsets.s FORCE
+ $(call filechk,offsets,__MSHV_ASM_OFFSETS_H__)
ifdef CONFIG_X86_64
obj-$(CONFIG_PARAVIRT_SPINLOCKS) += hv_spinlock.o
endif
+
+targets += mshv-asm-offsets.s
+clean-files += mshv-asm-offsets.h
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 042e8712d8de..636e9253b81e 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -9,12 +9,16 @@
#include <asm/apic.h>
#include <asm/boot.h>
#include <asm/desc.h>
+#include <asm/fpu/api.h>
+#include <asm/fpu/types.h>
#include <asm/i8259.h>
#include <asm/mshyperv.h>
#include <asm/msr.h>
#include <asm/realmode.h>
#include <asm/reboot.h>
+#include <asm/smap.h>
#include <../kernel/smpboot.h>
+#include "../../kernel/fpu/legacy.h"
extern struct boot_params boot_params;
static struct real_mode_header hv_vtl_real_mode_header;
@@ -249,3 +253,36 @@ int __init hv_vtl_early_init(void)
return 0;
}
+
+DEFINE_STATIC_CALL_NULL(__mshv_vtl_return_hypercall, void (*)(void));
+
+noinstr void mshv_vtl_return_hypercall(void)
+{
+ asm volatile ("call " STATIC_CALL_TRAMP_STR(__mshv_vtl_return_hypercall) :
+ ASM_CALL_CONSTRAINT);
+}
+
+extern void __mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0);
+
+void mshv_vtl_return_call_init(u64 vtl_return_offset)
+{
+ static_call_update(__mshv_vtl_return_hypercall,
+ (void *)((u8 *)hv_hypercall_pg + vtl_return_offset));
+}
+EXPORT_SYMBOL(mshv_vtl_return_call_init);
+
+void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0)
+{
+ struct hv_vp_assist_page *hvp;
+
+ hvp = hv_vp_assist_page[smp_processor_id()];
+ hvp->vtl_ret_x64rax = vtl0->rax;
+ hvp->vtl_ret_x64rcx = vtl0->rcx;
+
+ kernel_fpu_begin_mask(0);
+ fxrstor(&vtl0->fx_state);
+ __mshv_vtl_return_call(vtl0);
+ fxsave(&vtl0->fx_state);
+ kernel_fpu_end();
+}
+EXPORT_SYMBOL(mshv_vtl_return_call);
diff --git a/arch/x86/hyperv/mshv-asm-offsets.c b/arch/x86/hyperv/mshv-asm-offsets.c
new file mode 100644
index 000000000000..882c1db6df16
--- /dev/null
+++ b/arch/x86/hyperv/mshv-asm-offsets.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generate definitions needed by assembly language modules.
+ * This code generates raw asm output which is post-processed to extract
+ * and format the required data.
+ *
+ * Copyright (c) 2025, Microsoft Corporation.
+ *
+ * Author:
+ * Naman Jain <namjain@microsoft.com>
+ */
+#define COMPILE_OFFSETS
+
+#include <linux/kbuild.h>
+#include <asm/mshyperv.h>
+
+static void __used common(void)
+{
+ if (IS_ENABLED(CONFIG_HYPERV_VTL_MODE)) {
+ OFFSET(MSHV_VTL_CPU_CONTEXT_rax, mshv_vtl_cpu_context, rax);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_rcx, mshv_vtl_cpu_context, rcx);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_rdx, mshv_vtl_cpu_context, rdx);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_rbx, mshv_vtl_cpu_context, rbx);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_rbp, mshv_vtl_cpu_context, rbp);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_rsi, mshv_vtl_cpu_context, rsi);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_rdi, mshv_vtl_cpu_context, rdi);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_r8, mshv_vtl_cpu_context, r8);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_r9, mshv_vtl_cpu_context, r9);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_r10, mshv_vtl_cpu_context, r10);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_r11, mshv_vtl_cpu_context, r11);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_r12, mshv_vtl_cpu_context, r12);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_r13, mshv_vtl_cpu_context, r13);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_r14, mshv_vtl_cpu_context, r14);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_r15, mshv_vtl_cpu_context, r15);
+ OFFSET(MSHV_VTL_CPU_CONTEXT_cr2, mshv_vtl_cpu_context, cr2);
+ }
+}
diff --git a/arch/x86/hyperv/mshv_vtl_asm.S b/arch/x86/hyperv/mshv_vtl_asm.S
new file mode 100644
index 000000000000..4085073a5876
--- /dev/null
+++ b/arch/x86/hyperv/mshv_vtl_asm.S
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Assembly level code for mshv_vtl VTL transition
+ *
+ * Copyright (c) 2025, Microsoft Corporation.
+ *
+ * Author:
+ * Naman Jain <namjain@microsoft.com>
+ */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/frame.h>
+#include "mshv-asm-offsets.h"
+
+ .text
+ .section .noinstr.text, "ax"
+/*
+ * void __mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0)
+ */
+SYM_FUNC_START(__mshv_vtl_return_call)
+ /* Push callee save registers */
+ pushq %rbp
+ mov %rsp, %rbp
+ pushq %r12
+ pushq %r13
+ pushq %r14
+ pushq %r15
+ pushq %rbx
+
+ /* register switch to VTL0 clobbers all registers except rax/rcx */
+ mov %_ASM_ARG1, %rax
+
+ /* grab rbx/rbp/rsi/rdi/r8-r15 */
+ mov MSHV_VTL_CPU_CONTEXT_rbx(%rax), %rbx
+ mov MSHV_VTL_CPU_CONTEXT_rbp(%rax), %rbp
+ mov MSHV_VTL_CPU_CONTEXT_rsi(%rax), %rsi
+ mov MSHV_VTL_CPU_CONTEXT_rdi(%rax), %rdi
+ mov MSHV_VTL_CPU_CONTEXT_r8(%rax), %r8
+ mov MSHV_VTL_CPU_CONTEXT_r9(%rax), %r9
+ mov MSHV_VTL_CPU_CONTEXT_r10(%rax), %r10
+ mov MSHV_VTL_CPU_CONTEXT_r11(%rax), %r11
+ mov MSHV_VTL_CPU_CONTEXT_r12(%rax), %r12
+ mov MSHV_VTL_CPU_CONTEXT_r13(%rax), %r13
+ mov MSHV_VTL_CPU_CONTEXT_r14(%rax), %r14
+ mov MSHV_VTL_CPU_CONTEXT_r15(%rax), %r15
+
+ mov MSHV_VTL_CPU_CONTEXT_cr2(%rax), %rdx
+ mov %rdx, %cr2
+ mov MSHV_VTL_CPU_CONTEXT_rdx(%rax), %rdx
+
+ /* stash host registers on stack */
+ pushq %rax
+ pushq %rcx
+
+ xor %ecx, %ecx
+
+ /* make a hypercall to switch VTL */
+ call mshv_vtl_return_hypercall
+
+ /* stash guest registers on stack, restore saved host copies */
+ pushq %rax
+ pushq %rcx
+ mov 16(%rsp), %rcx
+ mov 24(%rsp), %rax
+
+ pop MSHV_VTL_CPU_CONTEXT_rcx(%rax)
+ pop MSHV_VTL_CPU_CONTEXT_rax(%rax)
+ add $16, %rsp
+
+ /* save rbx/rbp/rsi/rdi/r8-r15 */
+ mov %rbx, MSHV_VTL_CPU_CONTEXT_rbx(%rax)
+ mov %rbp, MSHV_VTL_CPU_CONTEXT_rbp(%rax)
+ mov %rsi, MSHV_VTL_CPU_CONTEXT_rsi(%rax)
+ mov %rdi, MSHV_VTL_CPU_CONTEXT_rdi(%rax)
+ mov %r8, MSHV_VTL_CPU_CONTEXT_r8(%rax)
+ mov %r9, MSHV_VTL_CPU_CONTEXT_r9(%rax)
+ mov %r10, MSHV_VTL_CPU_CONTEXT_r10(%rax)
+ mov %r11, MSHV_VTL_CPU_CONTEXT_r11(%rax)
+ mov %r12, MSHV_VTL_CPU_CONTEXT_r12(%rax)
+ mov %r13, MSHV_VTL_CPU_CONTEXT_r13(%rax)
+ mov %r14, MSHV_VTL_CPU_CONTEXT_r14(%rax)
+ mov %r15, MSHV_VTL_CPU_CONTEXT_r15(%rax)
+
+ /* pop callee-save registers r12-r15, rbx */
+ pop %rbx
+ pop %r15
+ pop %r14
+ pop %r13
+ pop %r12
+
+ pop %rbp
+ RET
+SYM_FUNC_END(__mshv_vtl_return_call)
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 605abd02158d..254974ccd98c 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -11,6 +11,7 @@
#include <asm/paravirt.h>
#include <asm/msr.h>
#include <hyperv/hvhdk.h>
+#include <asm/fpu/types.h>
/*
* Hyper-V always provides a single IO-APIC at this MMIO address.
@@ -260,13 +261,44 @@ static inline u64 hv_get_non_nested_msr(unsigned int reg) { return 0; }
static inline int hv_apicid_to_vp_index(u32 apic_id) { return -EINVAL; }
#endif /* CONFIG_HYPERV */
+struct mshv_vtl_cpu_context {
+ union {
+ struct {
+ u64 rax;
+ u64 rcx;
+ u64 rdx;
+ u64 rbx;
+ u64 cr2;
+ u64 rbp;
+ u64 rsi;
+ u64 rdi;
+ u64 r8;
+ u64 r9;
+ u64 r10;
+ u64 r11;
+ u64 r12;
+ u64 r13;
+ u64 r14;
+ u64 r15;
+ };
+ u64 gp_regs[16];
+ };
+
+ struct fxregs_state fx_state;
+};
#ifdef CONFIG_HYPERV_VTL_MODE
void __init hv_vtl_init_platform(void);
int __init hv_vtl_early_init(void);
+void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0);
+void mshv_vtl_return_call_init(u64 vtl_return_offset);
+void mshv_vtl_return_hypercall(void);
#else
static inline void __init hv_vtl_init_platform(void) {}
static inline int __init hv_vtl_early_init(void) { return 0; }
+static inline void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0) {}
+static inline void mshv_vtl_return_call_init(u64 vtl_return_offset) {}
+static inline void mshv_vtl_return_hypercall(void) {}
#endif
#include <asm-generic/mshyperv.h>
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 0b8c391a0342..cca2ae463128 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -17,7 +17,8 @@ config HYPERV
config HYPERV_VTL_MODE
bool "Enable Linux to boot in VTL context"
- depends on (X86_64 || ARM64) && HYPERV
+ depends on (X86_64 && HAVE_STATIC_CALL) || ARM64
+ depends on HYPERV
depends on SMP
default n
help
@@ -82,4 +83,27 @@ config MSHV_ROOT
If unsure, say N.
+config MSHV_VTL
+ tristate "Microsoft Hyper-V VTL driver"
+ depends on X86_64 && HYPERV_VTL_MODE
+ # Mapping VTL0 memory to a userspace process in VTL2 is supported in OpenHCL.
+ # VTL2 for OpenHCL makes use of Huge Pages to improve performance on VMs,
+ # specially with large memory requirements.
+ depends on TRANSPARENT_HUGEPAGE
+ # MTRRs are controlled by VTL0, and are not specific to individual VTLs.
+ # Therefore, do not attempt to access or modify MTRRs here.
+ depends on !MTRR
+ select CPUMASK_OFFSTACK
+ select VIRT_XFER_TO_GUEST_WORK
+ default n
+ help
+ Select this option to enable Hyper-V VTL driver support.
+ This driver provides interfaces for Virtual Machine Manager (VMM) running in VTL2
+ userspace to create VTLs and partitions, setup and manage VTL0 memory and
+ allow userspace to make direct hypercalls. This also allows to map VTL0's address
+ space to a usermode process in VTL2 and supports getting new VMBus messages and channel
+ events in VTL2.
+
+ If unsure, say N.
+
endmenu
diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
index 1a1677bf4dac..58b8d07639f3 100644
--- a/drivers/hv/Makefile
+++ b/drivers/hv/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_HYPERV_VMBUS) += hv_vmbus.o
obj-$(CONFIG_HYPERV_UTILS) += hv_utils.o
obj-$(CONFIG_HYPERV_BALLOON) += hv_balloon.o
obj-$(CONFIG_MSHV_ROOT) += mshv_root.o
+obj-$(CONFIG_MSHV_VTL) += mshv_vtl.o
CFLAGS_hv_trace.o = -I$(src)
CFLAGS_hv_balloon.o = -I$(src)
@@ -14,7 +15,11 @@ hv_vmbus-$(CONFIG_HYPERV_TESTING) += hv_debugfs.o
hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o hv_utils_transport.o
mshv_root-y := mshv_root_main.o mshv_synic.o mshv_eventfd.o mshv_irq.o \
mshv_root_hv_call.o mshv_portid_table.o
+mshv_vtl-y := mshv_vtl_main.o
# Code that must be built-in
obj-$(CONFIG_HYPERV) += hv_common.o
-obj-$(subst m,y,$(CONFIG_MSHV_ROOT)) += hv_proc.o mshv_common.o
+obj-$(subst m,y,$(CONFIG_MSHV_ROOT)) += hv_proc.o
+ifneq ($(CONFIG_MSHV_ROOT) $(CONFIG_MSHV_VTL),)
+ obj-y += mshv_common.o
+endif
diff --git a/drivers/hv/mshv_vtl.h b/drivers/hv/mshv_vtl.h
new file mode 100644
index 000000000000..a6eea52f7aa2
--- /dev/null
+++ b/drivers/hv/mshv_vtl.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _MSHV_VTL_H
+#define _MSHV_VTL_H
+
+#include <linux/mshv.h>
+#include <linux/types.h>
+
+struct mshv_vtl_run {
+ u32 cancel;
+ u32 vtl_ret_action_size;
+ u32 pad[2];
+ char exit_message[MSHV_MAX_RUN_MSG_SIZE];
+ union {
+ struct mshv_vtl_cpu_context cpu_context;
+
+ /*
+ * Reserving room for the cpu context to grow and to maintain compatibility
+ * with user mode.
+ */
+ char reserved[1024];
+ };
+ char vtl_ret_actions[MSHV_MAX_RUN_MSG_SIZE];
+};
+
+#endif /* _MSHV_VTL_H */
diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
new file mode 100644
index 000000000000..2cebe9de5a5a
--- /dev/null
+++ b/drivers/hv/mshv_vtl_main.c
@@ -0,0 +1,1392 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023, Microsoft Corporation.
+ *
+ * Author:
+ * Roman Kisel <romank@linux.microsoft.com>
+ * Saurabh Sengar <ssengar@linux.microsoft.com>
+ * Naman Jain <namjain@linux.microsoft.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/anon_inodes.h>
+#include <linux/cpuhotplug.h>
+#include <linux/count_zeros.h>
+#include <linux/entry-virt.h>
+#include <linux/eventfd.h>
+#include <linux/poll.h>
+#include <linux/file.h>
+#include <linux/vmalloc.h>
+#include <asm/debugreg.h>
+#include <asm/mshyperv.h>
+#include <trace/events/ipi.h>
+#include <uapi/asm/mtrr.h>
+#include <uapi/linux/mshv.h>
+#include <hyperv/hvhdk.h>
+
+#include "../../kernel/fpu/legacy.h"
+#include "mshv.h"
+#include "mshv_vtl.h"
+#include "hyperv_vmbus.h"
+
+MODULE_AUTHOR("Microsoft");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Microsoft Hyper-V VTL Driver");
+
+#define MSHV_ENTRY_REASON_LOWER_VTL_CALL 0x1
+#define MSHV_ENTRY_REASON_INTERRUPT 0x2
+#define MSHV_ENTRY_REASON_INTERCEPT 0x3
+
+#define MSHV_REAL_OFF_SHIFT 16
+#define MSHV_PG_OFF_CPU_MASK (BIT_ULL(MSHV_REAL_OFF_SHIFT) - 1)
+#define MSHV_RUN_PAGE_OFFSET 0
+#define MSHV_REG_PAGE_OFFSET 1
+#define VTL2_VMBUS_SINT_INDEX 7
+
+static struct device *mem_dev;
+
+static struct tasklet_struct msg_dpc;
+static wait_queue_head_t fd_wait_queue;
+static bool has_message;
+static struct eventfd_ctx *flag_eventfds[HV_EVENT_FLAGS_COUNT];
+static DEFINE_MUTEX(flag_lock);
+static bool __read_mostly mshv_has_reg_page;
+
+/* hvcall code is of type u16, allocate a bitmap of size (1 << 16) to accommodate it */
+#define MAX_BITMAP_SIZE ((U16_MAX + 1) / 8)
+
+struct mshv_vtl_hvcall_fd {
+ u8 allow_bitmap[MAX_BITMAP_SIZE];
+ bool allow_map_initialized;
+ /*
+ * Used to protect hvcall setup in IOCTLs
+ */
+ struct mutex init_mutex;
+ struct miscdevice *dev;
+};
+
+struct mshv_vtl_poll_file {
+ struct file *file;
+ wait_queue_entry_t wait;
+ wait_queue_head_t *wqh;
+ poll_table pt;
+ int cpu;
+};
+
+struct mshv_vtl {
+ struct device *module_dev;
+ u64 id;
+};
+
+struct mshv_vtl_per_cpu {
+ struct mshv_vtl_run *run;
+ struct page *reg_page;
+};
+
+/* SYNIC_OVERLAY_PAGE_MSR - internal, identical to hv_synic_simp */
+union hv_synic_overlay_page_msr {
+ u64 as_uint64;
+ struct {
+ u64 enabled: 1;
+ u64 reserved: 11;
+ u64 pfn: 52;
+ } __packed;
+};
+
+static struct mutex mshv_vtl_poll_file_lock;
+static union hv_register_vsm_page_offsets mshv_vsm_page_offsets;
+static union hv_register_vsm_capabilities mshv_vsm_capabilities;
+
+static DEFINE_PER_CPU(struct mshv_vtl_poll_file, mshv_vtl_poll_file);
+static DEFINE_PER_CPU(unsigned long long, num_vtl0_transitions);
+static DEFINE_PER_CPU(struct mshv_vtl_per_cpu, mshv_vtl_per_cpu);
+
+static const union hv_input_vtl input_vtl_zero;
+static const union hv_input_vtl input_vtl_normal = {
+ .use_target_vtl = 1,
+};
+
+static const struct file_operations mshv_vtl_fops;
+
+static long
+mshv_ioctl_create_vtl(void __user *user_arg, struct device *module_dev)
+{
+ struct mshv_vtl *vtl;
+ struct file *file;
+ int fd;
+
+ vtl = kzalloc(sizeof(*vtl), GFP_KERNEL);
+ if (!vtl)
+ return -ENOMEM;
+
+ fd = get_unused_fd_flags(O_CLOEXEC);
+ if (fd < 0) {
+ kfree(vtl);
+ return fd;
+ }
+ file = anon_inode_getfile("mshv_vtl", &mshv_vtl_fops,
+ vtl, O_RDWR);
+ if (IS_ERR(file)) {
+ kfree(vtl);
+ return PTR_ERR(file);
+ }
+ vtl->module_dev = module_dev;
+ fd_install(fd, file);
+
+ return fd;
+}
+
+static long
+mshv_ioctl_check_extension(void __user *user_arg)
+{
+ u32 arg;
+
+ if (copy_from_user(&arg, user_arg, sizeof(arg)))
+ return -EFAULT;
+
+ switch (arg) {
+ case MSHV_CAP_CORE_API_STABLE:
+ return 0;
+ case MSHV_CAP_REGISTER_PAGE:
+ return mshv_has_reg_page;
+ case MSHV_CAP_VTL_RETURN_ACTION:
+ return mshv_vsm_capabilities.return_action_available;
+ case MSHV_CAP_DR6_SHARED:
+ return mshv_vsm_capabilities.dr6_shared;
+ }
+
+ return -EOPNOTSUPP;
+}
+
+static long
+mshv_dev_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
+{
+ struct miscdevice *misc = filp->private_data;
+
+ switch (ioctl) {
+ case MSHV_CHECK_EXTENSION:
+ return mshv_ioctl_check_extension((void __user *)arg);
+ case MSHV_CREATE_VTL:
+ return mshv_ioctl_create_vtl((void __user *)arg, misc->this_device);
+ }
+
+ return -ENOTTY;
+}
+
+static const struct file_operations mshv_dev_fops = {
+ .owner = THIS_MODULE,
+ .unlocked_ioctl = mshv_dev_ioctl,
+ .llseek = noop_llseek,
+};
+
+static struct miscdevice mshv_dev = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "mshv",
+ .fops = &mshv_dev_fops,
+ .mode = 0600,
+};
+
+static struct mshv_vtl_run *mshv_vtl_this_run(void)
+{
+ return *this_cpu_ptr(&mshv_vtl_per_cpu.run);
+}
+
+static struct mshv_vtl_run *mshv_vtl_cpu_run(int cpu)
+{
+ return *per_cpu_ptr(&mshv_vtl_per_cpu.run, cpu);
+}
+
+static struct page *mshv_vtl_cpu_reg_page(int cpu)
+{
+ return *per_cpu_ptr(&mshv_vtl_per_cpu.reg_page, cpu);
+}
+
+static void mshv_vtl_configure_reg_page(struct mshv_vtl_per_cpu *per_cpu)
+{
+ struct hv_register_assoc reg_assoc = {};
+ union hv_synic_overlay_page_msr overlay = {};
+ struct page *reg_page;
+
+ reg_page = alloc_page(GFP_KERNEL | __GFP_ZERO | __GFP_RETRY_MAYFAIL);
+ if (!reg_page) {
+ WARN(1, "failed to allocate register page\n");
+ return;
+ }
+
+ overlay.enabled = 1;
+ overlay.pfn = page_to_hvpfn(reg_page);
+ reg_assoc.name = HV_X64_REGISTER_REG_PAGE;
+ reg_assoc.value.reg64 = overlay.as_uint64;
+
+ if (hv_call_set_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
+ 1, input_vtl_zero, ®_assoc)) {
+ WARN(1, "failed to setup register page\n");
+ __free_page(reg_page);
+ return;
+ }
+
+ per_cpu->reg_page = reg_page;
+ mshv_has_reg_page = true;
+}
+
+static void mshv_vtl_synic_enable_regs(unsigned int cpu)
+{
+ union hv_synic_sint sint;
+
+ sint.as_uint64 = 0;
+ sint.vector = HYPERVISOR_CALLBACK_VECTOR;
+ sint.masked = false;
+ sint.auto_eoi = hv_recommend_using_aeoi();
+
+ /* Enable intercepts */
+ if (!mshv_vsm_capabilities.intercept_page_available)
+ hv_set_msr(HV_MSR_SINT0 + HV_SYNIC_INTERCEPTION_SINT_INDEX,
+ sint.as_uint64);
+
+ /* VTL2 Host VSP SINT is (un)masked when the user mode requests that */
+}
+
+static int mshv_vtl_get_vsm_regs(void)
+{
+ struct hv_register_assoc registers[2];
+ int ret, count = 2;
+
+ registers[0].name = HV_REGISTER_VSM_CODE_PAGE_OFFSETS;
+ registers[1].name = HV_REGISTER_VSM_CAPABILITIES;
+
+ ret = hv_call_get_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
+ count, input_vtl_zero, registers);
+ if (ret)
+ return ret;
+
+ mshv_vsm_page_offsets.as_uint64 = registers[0].value.reg64;
+ mshv_vsm_capabilities.as_uint64 = registers[1].value.reg64;
+
+ return ret;
+}
+
+static int mshv_vtl_configure_vsm_partition(struct device *dev)
+{
+ union hv_register_vsm_partition_config config;
+ struct hv_register_assoc reg_assoc;
+
+ config.as_uint64 = 0;
+ config.default_vtl_protection_mask = HV_MAP_GPA_PERMISSIONS_MASK;
+ config.enable_vtl_protection = 1;
+ config.zero_memory_on_reset = 1;
+ config.intercept_vp_startup = 1;
+ config.intercept_cpuid_unimplemented = 1;
+
+ if (mshv_vsm_capabilities.intercept_page_available) {
+ dev_dbg(dev, "using intercept page\n");
+ config.intercept_page = 1;
+ }
+
+ reg_assoc.name = HV_REGISTER_VSM_PARTITION_CONFIG;
+ reg_assoc.value.reg64 = config.as_uint64;
+
+ return hv_call_set_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
+ 1, input_vtl_zero, ®_assoc);
+}
+
+static void mshv_vtl_vmbus_isr(void)
+{
+ struct hv_per_cpu_context *per_cpu;
+ struct hv_message *msg;
+ u32 message_type;
+ union hv_synic_event_flags *event_flags;
+ struct eventfd_ctx *eventfd;
+ u16 i;
+
+ per_cpu = this_cpu_ptr(hv_context.cpu_context);
+ if (smp_processor_id() == 0) {
+ msg = (struct hv_message *)per_cpu->hyp_synic_message_page + VTL2_VMBUS_SINT_INDEX;
+ message_type = READ_ONCE(msg->header.message_type);
+ if (message_type != HVMSG_NONE)
+ tasklet_schedule(&msg_dpc);
+ }
+
+ event_flags = (union hv_synic_event_flags *)per_cpu->hyp_synic_event_page +
+ VTL2_VMBUS_SINT_INDEX;
+ for_each_set_bit(i, event_flags->flags, HV_EVENT_FLAGS_COUNT) {
+ if (!sync_test_and_clear_bit(i, event_flags->flags))
+ continue;
+ rcu_read_lock();
+ eventfd = READ_ONCE(flag_eventfds[i]);
+ if (eventfd)
+ eventfd_signal(eventfd);
+ rcu_read_unlock();
+ }
+
+ vmbus_isr();
+}
+
+static int mshv_vtl_alloc_context(unsigned int cpu)
+{
+ struct mshv_vtl_per_cpu *per_cpu = this_cpu_ptr(&mshv_vtl_per_cpu);
+
+ per_cpu->run = (struct mshv_vtl_run *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+ if (!per_cpu->run)
+ return -ENOMEM;
+
+ if (mshv_vsm_capabilities.intercept_page_available)
+ mshv_vtl_configure_reg_page(per_cpu);
+
+ mshv_vtl_synic_enable_regs(cpu);
+
+ return 0;
+}
+
+static int mshv_vtl_cpuhp_online;
+
+static int hv_vtl_setup_synic(void)
+{
+ int ret;
+
+ /* Use our isr to first filter out packets destined for userspace */
+ hv_setup_vmbus_handler(mshv_vtl_vmbus_isr);
+
+ ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hyperv/vtl:online",
+ mshv_vtl_alloc_context, NULL);
+ if (ret < 0) {
+ hv_setup_vmbus_handler(vmbus_isr);
+ return ret;
+ }
+
+ mshv_vtl_cpuhp_online = ret;
+
+ return 0;
+}
+
+static void hv_vtl_remove_synic(void)
+{
+ cpuhp_remove_state(mshv_vtl_cpuhp_online);
+ hv_setup_vmbus_handler(vmbus_isr);
+}
+
+static int vtl_get_vp_register(struct hv_register_assoc *reg)
+{
+ return hv_call_get_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
+ 1, input_vtl_normal, reg);
+}
+
+static int vtl_set_vp_register(struct hv_register_assoc *reg)
+{
+ return hv_call_set_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
+ 1, input_vtl_normal, reg);
+}
+
+static int mshv_vtl_ioctl_add_vtl0_mem(struct mshv_vtl *vtl, void __user *arg)
+{
+ struct mshv_vtl_ram_disposition vtl0_mem;
+ struct dev_pagemap *pgmap;
+ void *addr;
+
+ if (copy_from_user(&vtl0_mem, arg, sizeof(vtl0_mem)))
+ return -EFAULT;
+ /* vtl0_mem.last_pfn is excluded in the pagemap range for VTL0 as per design */
+ if (vtl0_mem.last_pfn <= vtl0_mem.start_pfn) {
+ dev_err(vtl->module_dev, "range start pfn (%llx) > end pfn (%llx)\n",
+ vtl0_mem.start_pfn, vtl0_mem.last_pfn);
+ return -EFAULT;
+ }
+
+ pgmap = kzalloc(sizeof(*pgmap), GFP_KERNEL);
+ if (!pgmap)
+ return -ENOMEM;
+
+ pgmap->ranges[0].start = PFN_PHYS(vtl0_mem.start_pfn);
+ pgmap->ranges[0].end = PFN_PHYS(vtl0_mem.last_pfn) - 1;
+ pgmap->nr_range = 1;
+ pgmap->type = MEMORY_DEVICE_GENERIC;
+
+ /*
+ * Determine the highest page order that can be used for the given memory range.
+ * This works best when the range is aligned; i.e. both the start and the length.
+ */
+ pgmap->vmemmap_shift = count_trailing_zeros(vtl0_mem.start_pfn | vtl0_mem.last_pfn);
+ dev_dbg(vtl->module_dev,
+ "Add VTL0 memory: start: 0x%llx, end_pfn: 0x%llx, page order: %lu\n",
+ vtl0_mem.start_pfn, vtl0_mem.last_pfn, pgmap->vmemmap_shift);
+
+ addr = devm_memremap_pages(mem_dev, pgmap);
+ if (IS_ERR(addr)) {
+ dev_err(vtl->module_dev, "devm_memremap_pages error: %ld\n", PTR_ERR(addr));
+ kfree(pgmap);
+ return -EFAULT;
+ }
+
+ /* Don't free pgmap, since it has to stick around until the memory
+ * is unmapped, which will never happen as there is no scenario
+ * where VTL0 can be released/shutdown without bringing down VTL2.
+ */
+ return 0;
+}
+
+static void mshv_vtl_cancel(int cpu)
+{
+ int here = get_cpu();
+
+ if (here != cpu) {
+ if (!xchg_relaxed(&mshv_vtl_cpu_run(cpu)->cancel, 1))
+ smp_send_reschedule(cpu);
+ } else {
+ WRITE_ONCE(mshv_vtl_this_run()->cancel, 1);
+ }
+ put_cpu();
+}
+
+static int mshv_vtl_poll_file_wake(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key)
+{
+ struct mshv_vtl_poll_file *poll_file = container_of(wait, struct mshv_vtl_poll_file, wait);
+
+ mshv_vtl_cancel(poll_file->cpu);
+
+ return 0;
+}
+
+static void mshv_vtl_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh, poll_table *pt)
+{
+ struct mshv_vtl_poll_file *poll_file = container_of(pt, struct mshv_vtl_poll_file, pt);
+
+ WARN_ON(poll_file->wqh);
+ poll_file->wqh = wqh;
+ add_wait_queue(wqh, &poll_file->wait);
+}
+
+static int mshv_vtl_ioctl_set_poll_file(struct mshv_vtl_set_poll_file __user *user_input)
+{
+ struct file *file, *old_file;
+ struct mshv_vtl_poll_file *poll_file;
+ struct mshv_vtl_set_poll_file input;
+
+ if (copy_from_user(&input, user_input, sizeof(input)))
+ return -EFAULT;
+
+ if (input.cpu >= num_possible_cpus() || !cpu_online(input.cpu))
+ return -EINVAL;
+ /*
+ * CPU Hotplug is not supported in VTL2 in OpenHCL, where this kernel driver exists.
+ * CPU is expected to remain online after above cpu_online() check.
+ */
+
+ file = NULL;
+ file = fget(input.fd);
+ if (!file)
+ return -EBADFD;
+
+ poll_file = per_cpu_ptr(&mshv_vtl_poll_file, READ_ONCE(input.cpu));
+ if (!poll_file)
+ return -EINVAL;
+
+ mutex_lock(&mshv_vtl_poll_file_lock);
+
+ if (poll_file->wqh)
+ remove_wait_queue(poll_file->wqh, &poll_file->wait);
+ poll_file->wqh = NULL;
+
+ old_file = poll_file->file;
+ poll_file->file = file;
+ poll_file->cpu = input.cpu;
+
+ if (file) {
+ init_waitqueue_func_entry(&poll_file->wait, mshv_vtl_poll_file_wake);
+ init_poll_funcptr(&poll_file->pt, mshv_vtl_ptable_queue_proc);
+ vfs_poll(file, &poll_file->pt);
+ }
+
+ mutex_unlock(&mshv_vtl_poll_file_lock);
+
+ if (old_file)
+ fput(old_file);
+
+ return 0;
+}
+
+/* Static table mapping register names to their corresponding actions */
+static const struct {
+ enum hv_register_name reg_name;
+ int debug_reg_num; /* -1 if not a debug register */
+ u32 msr_addr; /* 0 if not an MSR */
+} reg_table[] = {
+ /* Debug registers */
+ {HV_X64_REGISTER_DR0, 0, 0},
+ {HV_X64_REGISTER_DR1, 1, 0},
+ {HV_X64_REGISTER_DR2, 2, 0},
+ {HV_X64_REGISTER_DR3, 3, 0},
+ {HV_X64_REGISTER_DR6, 6, 0},
+ /* MTRR MSRs */
+ {HV_X64_REGISTER_MSR_MTRR_CAP, -1, MSR_MTRRcap},
+ {HV_X64_REGISTER_MSR_MTRR_DEF_TYPE, -1, MSR_MTRRdefType},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE0, -1, MTRRphysBase_MSR(0)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE1, -1, MTRRphysBase_MSR(1)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE2, -1, MTRRphysBase_MSR(2)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE3, -1, MTRRphysBase_MSR(3)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE4, -1, MTRRphysBase_MSR(4)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE5, -1, MTRRphysBase_MSR(5)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE6, -1, MTRRphysBase_MSR(6)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE7, -1, MTRRphysBase_MSR(7)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE8, -1, MTRRphysBase_MSR(8)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASE9, -1, MTRRphysBase_MSR(9)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASEA, -1, MTRRphysBase_MSR(0xa)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASEB, -1, MTRRphysBase_MSR(0xb)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASEC, -1, MTRRphysBase_MSR(0xc)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASED, -1, MTRRphysBase_MSR(0xd)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASEE, -1, MTRRphysBase_MSR(0xe)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_BASEF, -1, MTRRphysBase_MSR(0xf)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK0, -1, MTRRphysMask_MSR(0)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK1, -1, MTRRphysMask_MSR(1)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK2, -1, MTRRphysMask_MSR(2)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK3, -1, MTRRphysMask_MSR(3)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK4, -1, MTRRphysMask_MSR(4)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK5, -1, MTRRphysMask_MSR(5)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK6, -1, MTRRphysMask_MSR(6)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK7, -1, MTRRphysMask_MSR(7)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK8, -1, MTRRphysMask_MSR(8)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASK9, -1, MTRRphysMask_MSR(9)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASKA, -1, MTRRphysMask_MSR(0xa)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASKB, -1, MTRRphysMask_MSR(0xb)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASKC, -1, MTRRphysMask_MSR(0xc)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASKD, -1, MTRRphysMask_MSR(0xd)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASKE, -1, MTRRphysMask_MSR(0xe)},
+ {HV_X64_REGISTER_MSR_MTRR_PHYS_MASKF, -1, MTRRphysMask_MSR(0xf)},
+ {HV_X64_REGISTER_MSR_MTRR_FIX64K00000, -1, MSR_MTRRfix64K_00000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX16K80000, -1, MSR_MTRRfix16K_80000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX16KA0000, -1, MSR_MTRRfix16K_A0000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX4KC0000, -1, MSR_MTRRfix4K_C0000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX4KC8000, -1, MSR_MTRRfix4K_C8000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX4KD0000, -1, MSR_MTRRfix4K_D0000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX4KD8000, -1, MSR_MTRRfix4K_D8000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX4KE0000, -1, MSR_MTRRfix4K_E0000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX4KE8000, -1, MSR_MTRRfix4K_E8000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX4KF0000, -1, MSR_MTRRfix4K_F0000},
+ {HV_X64_REGISTER_MSR_MTRR_FIX4KF8000, -1, MSR_MTRRfix4K_F8000},
+};
+
+static int mshv_vtl_get_set_reg(struct hv_register_assoc *regs, bool set)
+{
+ u64 *reg64;
+ enum hv_register_name gpr_name;
+ int i;
+
+ gpr_name = regs->name;
+ reg64 = ®s->value.reg64;
+
+ /* Search for the register in the table */
+ for (i = 0; i < ARRAY_SIZE(reg_table); i++) {
+ if (reg_table[i].reg_name != gpr_name)
+ continue;
+ if (reg_table[i].debug_reg_num != -1) {
+ /* Handle debug registers */
+ if (gpr_name == HV_X64_REGISTER_DR6 &&
+ !mshv_vsm_capabilities.dr6_shared)
+ goto hypercall;
+ if (set)
+ native_set_debugreg(reg_table[i].debug_reg_num, *reg64);
+ else
+ *reg64 = native_get_debugreg(reg_table[i].debug_reg_num);
+ } else {
+ /* Handle MSRs */
+ if (set)
+ wrmsrl(reg_table[i].msr_addr, *reg64);
+ else
+ rdmsrl(reg_table[i].msr_addr, *reg64);
+ }
+ return 0;
+ }
+
+hypercall:
+ return 1;
+}
+
+static void mshv_vtl_return(struct mshv_vtl_cpu_context *vtl0)
+{
+ struct hv_vp_assist_page *hvp;
+
+ hvp = hv_vp_assist_page[smp_processor_id()];
+
+ /*
+ * Process signal event direct set in the run page, if any.
+ */
+ if (mshv_vsm_capabilities.return_action_available) {
+ u32 offset = READ_ONCE(mshv_vtl_this_run()->vtl_ret_action_size);
+
+ WRITE_ONCE(mshv_vtl_this_run()->vtl_ret_action_size, 0);
+
+ /*
+ * Hypervisor will take care of clearing out the actions
+ * set in the assist page.
+ */
+ memcpy(hvp->vtl_ret_actions,
+ mshv_vtl_this_run()->vtl_ret_actions,
+ min_t(u32, offset, sizeof(hvp->vtl_ret_actions)));
+ }
+
+ mshv_vtl_return_call(vtl0);
+}
+
+static bool mshv_vtl_process_intercept(void)
+{
+ struct hv_per_cpu_context *mshv_cpu;
+ void *synic_message_page;
+ struct hv_message *msg;
+ u32 message_type;
+
+ mshv_cpu = this_cpu_ptr(hv_context.cpu_context);
+ synic_message_page = mshv_cpu->hyp_synic_message_page;
+ if (unlikely(!synic_message_page))
+ return true;
+
+ msg = (struct hv_message *)synic_message_page + HV_SYNIC_INTERCEPTION_SINT_INDEX;
+ message_type = READ_ONCE(msg->header.message_type);
+ if (message_type == HVMSG_NONE)
+ return true;
+
+ memcpy(mshv_vtl_this_run()->exit_message, msg, sizeof(*msg));
+ vmbus_signal_eom(msg, message_type);
+
+ return false;
+}
+
+static int mshv_vtl_ioctl_return_to_lower_vtl(void)
+{
+ preempt_disable();
+ for (;;) {
+ unsigned long irq_flags;
+ struct hv_vp_assist_page *hvp;
+ int ret;
+
+ if (__xfer_to_guest_mode_work_pending()) {
+ preempt_enable();
+ ret = xfer_to_guest_mode_handle_work();
+ if (ret)
+ return ret;
+ preempt_disable();
+ }
+
+ local_irq_save(irq_flags);
+ if (READ_ONCE(mshv_vtl_this_run()->cancel)) {
+ local_irq_restore(irq_flags);
+ preempt_enable();
+ return -EINTR;
+ }
+
+ mshv_vtl_return(&mshv_vtl_this_run()->cpu_context);
+ local_irq_restore(irq_flags);
+
+ hvp = hv_vp_assist_page[smp_processor_id()];
+ this_cpu_inc(num_vtl0_transitions);
+ switch (hvp->vtl_entry_reason) {
+ case MSHV_ENTRY_REASON_INTERRUPT:
+ if (!mshv_vsm_capabilities.intercept_page_available &&
+ likely(!mshv_vtl_process_intercept()))
+ goto done;
+ break;
+
+ case MSHV_ENTRY_REASON_INTERCEPT:
+ WARN_ON(!mshv_vsm_capabilities.intercept_page_available);
+ memcpy(mshv_vtl_this_run()->exit_message, hvp->intercept_message,
+ sizeof(hvp->intercept_message));
+ goto done;
+
+ default:
+ panic("unknown entry reason: %d", hvp->vtl_entry_reason);
+ }
+ }
+
+done:
+ preempt_enable();
+
+ return 0;
+}
+
+static long
+mshv_vtl_ioctl_get_regs(void __user *user_args)
+{
+ struct mshv_vp_registers args;
+ struct hv_register_assoc reg;
+ long ret;
+
+ if (copy_from_user(&args, user_args, sizeof(args)))
+ return -EFAULT;
+
+ /* This IOCTL supports processing only one register at a time. */
+ if (args.count != 1)
+ return -EINVAL;
+
+ if (copy_from_user(®, (void __user *)args.regs_ptr,
+ sizeof(reg)))
+ return -EFAULT;
+
+ ret = mshv_vtl_get_set_reg(®, false);
+ if (!ret)
+ goto copy_args; /* No need of hypercall */
+ ret = vtl_get_vp_register(®);
+ if (ret)
+ return ret;
+
+copy_args:
+ if (copy_to_user((void __user *)args.regs_ptr, ®, sizeof(reg)))
+ ret = -EFAULT;
+
+ return ret;
+}
+
+static long
+mshv_vtl_ioctl_set_regs(void __user *user_args)
+{
+ struct mshv_vp_registers args;
+ struct hv_register_assoc reg;
+ long ret;
+
+ if (copy_from_user(&args, user_args, sizeof(args)))
+ return -EFAULT;
+
+ /* This IOCTL supports processing only one register at a time. */
+ if (args.count != 1)
+ return -EINVAL;
+
+ if (copy_from_user(®, (void __user *)args.regs_ptr, sizeof(reg)))
+ return -EFAULT;
+
+ ret = mshv_vtl_get_set_reg(®, true);
+ if (!ret)
+ return ret; /* No need of hypercall */
+ ret = vtl_set_vp_register(®);
+
+ return ret;
+}
+
+static long
+mshv_vtl_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
+{
+ long ret;
+ struct mshv_vtl *vtl = filp->private_data;
+
+ switch (ioctl) {
+ case MSHV_SET_POLL_FILE:
+ ret = mshv_vtl_ioctl_set_poll_file((struct mshv_vtl_set_poll_file __user *)arg);
+ break;
+ case MSHV_GET_VP_REGISTERS:
+ ret = mshv_vtl_ioctl_get_regs((void __user *)arg);
+ break;
+ case MSHV_SET_VP_REGISTERS:
+ ret = mshv_vtl_ioctl_set_regs((void __user *)arg);
+ break;
+ case MSHV_RETURN_TO_LOWER_VTL:
+ ret = mshv_vtl_ioctl_return_to_lower_vtl();
+ break;
+ case MSHV_ADD_VTL0_MEMORY:
+ ret = mshv_vtl_ioctl_add_vtl0_mem(vtl, (void __user *)arg);
+ break;
+ default:
+ dev_err(vtl->module_dev, "invalid vtl ioctl: %#x\n", ioctl);
+ ret = -ENOTTY;
+ }
+
+ return ret;
+}
+
+static vm_fault_t mshv_vtl_fault(struct vm_fault *vmf)
+{
+ struct page *page;
+ int cpu = vmf->pgoff & MSHV_PG_OFF_CPU_MASK;
+ int real_off = vmf->pgoff >> MSHV_REAL_OFF_SHIFT;
+
+ if (!cpu_online(cpu))
+ return VM_FAULT_SIGBUS;
+ /*
+ * CPU Hotplug is not supported in VTL2 in OpenHCL, where this kernel driver exists.
+ * CPU is expected to remain online after above cpu_online() check.
+ */
+
+ if (real_off == MSHV_RUN_PAGE_OFFSET) {
+ page = virt_to_page(mshv_vtl_cpu_run(cpu));
+ } else if (real_off == MSHV_REG_PAGE_OFFSET) {
+ if (!mshv_has_reg_page)
+ return VM_FAULT_SIGBUS;
+ page = mshv_vtl_cpu_reg_page(cpu);
+ } else {
+ return VM_FAULT_NOPAGE;
+ }
+
+ get_page(page);
+ vmf->page = page;
+
+ return 0;
+}
+
+static const struct vm_operations_struct mshv_vtl_vm_ops = {
+ .fault = mshv_vtl_fault,
+};
+
+static int mshv_vtl_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+ vma->vm_ops = &mshv_vtl_vm_ops;
+
+ return 0;
+}
+
+static int mshv_vtl_release(struct inode *inode, struct file *filp)
+{
+ struct mshv_vtl *vtl = filp->private_data;
+
+ kfree(vtl);
+
+ return 0;
+}
+
+static const struct file_operations mshv_vtl_fops = {
+ .owner = THIS_MODULE,
+ .unlocked_ioctl = mshv_vtl_ioctl,
+ .release = mshv_vtl_release,
+ .mmap = mshv_vtl_mmap,
+};
+
+static void mshv_vtl_synic_mask_vmbus_sint(const u8 *mask)
+{
+ union hv_synic_sint sint;
+
+ sint.as_uint64 = 0;
+ sint.vector = HYPERVISOR_CALLBACK_VECTOR;
+ sint.masked = (*mask != 0);
+ sint.auto_eoi = hv_recommend_using_aeoi();
+
+ hv_set_msr(HV_MSR_SINT0 + VTL2_VMBUS_SINT_INDEX,
+ sint.as_uint64);
+
+ if (!sint.masked)
+ pr_debug("%s: Unmasking VTL2 VMBUS SINT on VP %d\n", __func__, smp_processor_id());
+ else
+ pr_debug("%s: Masking VTL2 VMBUS SINT on VP %d\n", __func__, smp_processor_id());
+}
+
+static void mshv_vtl_read_remote(void *buffer)
+{
+ struct hv_per_cpu_context *mshv_cpu = this_cpu_ptr(hv_context.cpu_context);
+ struct hv_message *msg = (struct hv_message *)mshv_cpu->hyp_synic_message_page +
+ VTL2_VMBUS_SINT_INDEX;
+ u32 message_type = READ_ONCE(msg->header.message_type);
+
+ WRITE_ONCE(has_message, false);
+ if (message_type == HVMSG_NONE)
+ return;
+
+ memcpy(buffer, msg, sizeof(*msg));
+ vmbus_signal_eom(msg, message_type);
+}
+
+static bool vtl_synic_mask_vmbus_sint_masked = true;
+
+static ssize_t mshv_vtl_sint_read(struct file *filp, char __user *arg, size_t size, loff_t *offset)
+{
+ struct hv_message msg = {};
+ int ret;
+
+ if (size < sizeof(msg))
+ return -EINVAL;
+
+ for (;;) {
+ smp_call_function_single(VMBUS_CONNECT_CPU, mshv_vtl_read_remote, &msg, true);
+ if (msg.header.message_type != HVMSG_NONE)
+ break;
+
+ if (READ_ONCE(vtl_synic_mask_vmbus_sint_masked))
+ return 0; /* EOF */
+
+ if (filp->f_flags & O_NONBLOCK)
+ return -EAGAIN;
+
+ ret = wait_event_interruptible(fd_wait_queue,
+ READ_ONCE(has_message) ||
+ READ_ONCE(vtl_synic_mask_vmbus_sint_masked));
+ if (ret)
+ return ret;
+ }
+
+ if (copy_to_user(arg, &msg, sizeof(msg)))
+ return -EFAULT;
+
+ return sizeof(msg);
+}
+
+static __poll_t mshv_vtl_sint_poll(struct file *filp, poll_table *wait)
+{
+ __poll_t mask = 0;
+
+ poll_wait(filp, &fd_wait_queue, wait);
+ if (READ_ONCE(has_message) || READ_ONCE(vtl_synic_mask_vmbus_sint_masked))
+ mask |= EPOLLIN | EPOLLRDNORM;
+
+ return mask;
+}
+
+static void mshv_vtl_sint_on_msg_dpc(unsigned long data)
+{
+ WRITE_ONCE(has_message, true);
+ wake_up_interruptible_poll(&fd_wait_queue, EPOLLIN);
+}
+
+static int mshv_vtl_sint_ioctl_post_msg(struct mshv_vtl_sint_post_msg __user *arg)
+{
+ struct mshv_vtl_sint_post_msg message;
+ u8 payload[HV_MESSAGE_PAYLOAD_BYTE_COUNT];
+
+ if (copy_from_user(&message, arg, sizeof(message)))
+ return -EFAULT;
+ if (message.payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
+ return -EINVAL;
+ if (copy_from_user(payload, (void __user *)message.payload_ptr,
+ message.payload_size))
+ return -EFAULT;
+
+ return hv_post_message((union hv_connection_id)message.connection_id,
+ message.message_type, (void *)payload,
+ message.payload_size);
+}
+
+static int mshv_vtl_sint_ioctl_signal_event(struct mshv_vtl_signal_event __user *arg)
+{
+ u64 input, status;
+ struct mshv_vtl_signal_event signal_event;
+
+ if (copy_from_user(&signal_event, arg, sizeof(signal_event)))
+ return -EFAULT;
+
+ input = signal_event.connection_id | ((u64)signal_event.flag << 32);
+
+ status = hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, input);
+
+ return hv_result_to_errno(status);
+}
+
+static int mshv_vtl_sint_ioctl_set_eventfd(struct mshv_vtl_set_eventfd __user *arg)
+{
+ struct mshv_vtl_set_eventfd set_eventfd;
+ struct eventfd_ctx *eventfd, *old_eventfd;
+
+ if (copy_from_user(&set_eventfd, arg, sizeof(set_eventfd)))
+ return -EFAULT;
+ if (set_eventfd.flag >= HV_EVENT_FLAGS_COUNT)
+ return -EINVAL;
+
+ eventfd = NULL;
+ if (set_eventfd.fd >= 0) {
+ eventfd = eventfd_ctx_fdget(set_eventfd.fd);
+ if (IS_ERR(eventfd))
+ return PTR_ERR(eventfd);
+ }
+
+ guard(mutex)(&flag_lock);
+ old_eventfd = READ_ONCE(flag_eventfds[set_eventfd.flag]);
+ WRITE_ONCE(flag_eventfds[set_eventfd.flag], eventfd);
+
+ if (old_eventfd) {
+ synchronize_rcu();
+ eventfd_ctx_put(old_eventfd);
+ }
+
+ return 0;
+}
+
+static int mshv_vtl_sint_ioctl_pause_msg_stream(struct mshv_sint_mask __user *arg)
+{
+ static DEFINE_MUTEX(vtl2_vmbus_sint_mask_mutex);
+ struct mshv_sint_mask mask;
+
+ if (copy_from_user(&mask, arg, sizeof(mask)))
+ return -EFAULT;
+ guard(mutex)(&vtl2_vmbus_sint_mask_mutex);
+ on_each_cpu((smp_call_func_t)mshv_vtl_synic_mask_vmbus_sint, &mask.mask, 1);
+ WRITE_ONCE(vtl_synic_mask_vmbus_sint_masked, mask.mask != 0);
+ if (mask.mask)
+ wake_up_interruptible_poll(&fd_wait_queue, EPOLLIN);
+
+ return 0;
+}
+
+static long mshv_vtl_sint_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
+{
+ switch (cmd) {
+ case MSHV_SINT_POST_MESSAGE:
+ return mshv_vtl_sint_ioctl_post_msg((struct mshv_vtl_sint_post_msg __user *)arg);
+ case MSHV_SINT_SIGNAL_EVENT:
+ return mshv_vtl_sint_ioctl_signal_event((struct mshv_vtl_signal_event __user *)arg);
+ case MSHV_SINT_SET_EVENTFD:
+ return mshv_vtl_sint_ioctl_set_eventfd((struct mshv_vtl_set_eventfd __user *)arg);
+ case MSHV_SINT_PAUSE_MESSAGE_STREAM:
+ return mshv_vtl_sint_ioctl_pause_msg_stream((struct mshv_sint_mask __user *)arg);
+ default:
+ return -ENOIOCTLCMD;
+ }
+}
+
+static const struct file_operations mshv_vtl_sint_ops = {
+ .owner = THIS_MODULE,
+ .read = mshv_vtl_sint_read,
+ .poll = mshv_vtl_sint_poll,
+ .unlocked_ioctl = mshv_vtl_sint_ioctl,
+};
+
+static struct miscdevice mshv_vtl_sint_dev = {
+ .name = "mshv_sint",
+ .fops = &mshv_vtl_sint_ops,
+ .mode = 0600,
+ .minor = MISC_DYNAMIC_MINOR,
+};
+
+static int mshv_vtl_hvcall_dev_open(struct inode *node, struct file *f)
+{
+ struct miscdevice *dev = f->private_data;
+ struct mshv_vtl_hvcall_fd *fd;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ fd = vzalloc(sizeof(*fd));
+ if (!fd)
+ return -ENOMEM;
+ fd->dev = dev;
+ f->private_data = fd;
+ mutex_init(&fd->init_mutex);
+
+ return 0;
+}
+
+static int mshv_vtl_hvcall_dev_release(struct inode *node, struct file *f)
+{
+ struct mshv_vtl_hvcall_fd *fd;
+
+ fd = f->private_data;
+ if (fd) {
+ vfree(fd);
+ f->private_data = NULL;
+ }
+
+ return 0;
+}
+
+static int mshv_vtl_hvcall_do_setup(struct mshv_vtl_hvcall_fd *fd,
+ struct mshv_vtl_hvcall_setup __user *hvcall_setup_user)
+{
+ struct mshv_vtl_hvcall_setup hvcall_setup;
+
+ guard(mutex)(&fd->init_mutex);
+
+ if (fd->allow_map_initialized) {
+ dev_err(fd->dev->this_device,
+ "Hypercall allow map has already been set, pid %d\n",
+ current->pid);
+ return -EINVAL;
+ }
+
+ if (copy_from_user(&hvcall_setup, hvcall_setup_user,
+ sizeof(struct mshv_vtl_hvcall_setup))) {
+ return -EFAULT;
+ }
+ if (hvcall_setup.bitmap_array_size > ARRAY_SIZE(fd->allow_bitmap))
+ return -EINVAL;
+
+ if (copy_from_user(&fd->allow_bitmap,
+ (void __user *)hvcall_setup.allow_bitmap_ptr,
+ hvcall_setup.bitmap_array_size)) {
+ return -EFAULT;
+ }
+
+ dev_info(fd->dev->this_device, "Hypercall allow map has been set, pid %d\n",
+ current->pid);
+ fd->allow_map_initialized = true;
+ return 0;
+}
+
+static bool mshv_vtl_hvcall_is_allowed(struct mshv_vtl_hvcall_fd *fd, u16 call_code)
+{
+ return test_bit(call_code, (unsigned long *)fd->allow_bitmap);
+}
+
+static int mshv_vtl_hvcall_call(struct mshv_vtl_hvcall_fd *fd,
+ struct mshv_vtl_hvcall __user *hvcall_user)
+{
+ struct mshv_vtl_hvcall hvcall;
+ void *in, *out;
+ int ret;
+
+ if (copy_from_user(&hvcall, hvcall_user, sizeof(struct mshv_vtl_hvcall)))
+ return -EFAULT;
+ if (hvcall.input_size > HV_HYP_PAGE_SIZE)
+ return -EINVAL;
+ if (hvcall.output_size > HV_HYP_PAGE_SIZE)
+ return -EINVAL;
+
+ /*
+ * By default, all hypercalls are not allowed.
+ * The user mode code has to set up the allow bitmap once.
+ */
+
+ if (!mshv_vtl_hvcall_is_allowed(fd, hvcall.control & 0xFFFF)) {
+ dev_err(fd->dev->this_device,
+ "Hypercall with control data %#llx isn't allowed\n",
+ hvcall.control);
+ return -EPERM;
+ }
+
+ /*
+ * This may create a problem for Confidential VM (CVM) usecase where we need to use
+ * Hyper-V driver allocated per-cpu input and output pages (hyperv_pcpu_input_arg and
+ * hyperv_pcpu_output_arg) for making a hypervisor call.
+ *
+ * TODO: Take care of this when CVM support is added.
+ */
+ in = (void *)__get_free_page(GFP_KERNEL);
+ out = (void *)__get_free_page(GFP_KERNEL);
+
+ if (copy_from_user(in, (void __user *)hvcall.input_ptr, hvcall.input_size)) {
+ ret = -EFAULT;
+ goto free_pages;
+ }
+
+ hvcall.status = hv_do_hypercall(hvcall.control, in, out);
+
+ if (copy_to_user((void __user *)hvcall.output_ptr, out, hvcall.output_size)) {
+ ret = -EFAULT;
+ goto free_pages;
+ }
+ ret = put_user(hvcall.status, &hvcall_user->status);
+free_pages:
+ free_page((unsigned long)in);
+ free_page((unsigned long)out);
+
+ return ret;
+}
+
+static long mshv_vtl_hvcall_dev_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
+{
+ struct mshv_vtl_hvcall_fd *fd = f->private_data;
+
+ switch (cmd) {
+ case MSHV_HVCALL_SETUP:
+ return mshv_vtl_hvcall_do_setup(fd, (struct mshv_vtl_hvcall_setup __user *)arg);
+ case MSHV_HVCALL:
+ return mshv_vtl_hvcall_call(fd, (struct mshv_vtl_hvcall __user *)arg);
+ default:
+ break;
+ }
+
+ return -ENOIOCTLCMD;
+}
+
+static const struct file_operations mshv_vtl_hvcall_dev_file_ops = {
+ .owner = THIS_MODULE,
+ .open = mshv_vtl_hvcall_dev_open,
+ .release = mshv_vtl_hvcall_dev_release,
+ .unlocked_ioctl = mshv_vtl_hvcall_dev_ioctl,
+};
+
+static struct miscdevice mshv_vtl_hvcall_dev = {
+ .name = "mshv_hvcall",
+ .nodename = "mshv_hvcall",
+ .fops = &mshv_vtl_hvcall_dev_file_ops,
+ .mode = 0600,
+ .minor = MISC_DYNAMIC_MINOR,
+};
+
+static int mshv_vtl_low_open(struct inode *inodep, struct file *filp)
+{
+ pid_t pid = task_pid_vnr(current);
+ uid_t uid = current_uid().val;
+ int ret = 0;
+
+ pr_debug("%s: Opening VTL low, task group %d, uid %d\n", __func__, pid, uid);
+
+ if (capable(CAP_SYS_ADMIN)) {
+ filp->private_data = inodep;
+ } else {
+ pr_err("%s: VTL low open failed: CAP_SYS_ADMIN required. task group %d, uid %d",
+ __func__, pid, uid);
+ ret = -EPERM;
+ }
+
+ return ret;
+}
+
+static bool can_fault(struct vm_fault *vmf, unsigned long size, unsigned long *pfn)
+{
+ unsigned long mask = size - 1;
+ unsigned long start = vmf->address & ~mask;
+ unsigned long end = start + size;
+ bool is_valid;
+
+ is_valid = (vmf->address & mask) == ((vmf->pgoff << PAGE_SHIFT) & mask) &&
+ start >= vmf->vma->vm_start &&
+ end <= vmf->vma->vm_end;
+
+ if (is_valid)
+ *pfn = vmf->pgoff & ~(mask >> PAGE_SHIFT);
+
+ return is_valid;
+}
+
+static vm_fault_t mshv_vtl_low_huge_fault(struct vm_fault *vmf, unsigned int order)
+{
+ unsigned long pfn = vmf->pgoff;
+ vm_fault_t ret = VM_FAULT_FALLBACK;
+
+ switch (order) {
+ case 0:
+ return vmf_insert_mixed(vmf->vma, vmf->address, pfn);
+
+ case PMD_ORDER:
+ if (can_fault(vmf, PMD_SIZE, &pfn))
+ ret = vmf_insert_pfn_pmd(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
+ return ret;
+
+ case PUD_ORDER:
+ if (can_fault(vmf, PUD_SIZE, &pfn))
+ ret = vmf_insert_pfn_pud(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
+ return ret;
+
+ default:
+ return VM_FAULT_SIGBUS;
+ }
+}
+
+static vm_fault_t mshv_vtl_low_fault(struct vm_fault *vmf)
+{
+ return mshv_vtl_low_huge_fault(vmf, 0);
+}
+
+static const struct vm_operations_struct mshv_vtl_low_vm_ops = {
+ .fault = mshv_vtl_low_fault,
+ .huge_fault = mshv_vtl_low_huge_fault,
+};
+
+static int mshv_vtl_low_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+ vma->vm_ops = &mshv_vtl_low_vm_ops;
+ vm_flags_set(vma, VM_HUGEPAGE | VM_MIXEDMAP);
+
+ return 0;
+}
+
+static const struct file_operations mshv_vtl_low_file_ops = {
+ .owner = THIS_MODULE,
+ .open = mshv_vtl_low_open,
+ .mmap = mshv_vtl_low_mmap,
+};
+
+static struct miscdevice mshv_vtl_low = {
+ .name = "mshv_vtl_low",
+ .nodename = "mshv_vtl_low",
+ .fops = &mshv_vtl_low_file_ops,
+ .mode = 0600,
+ .minor = MISC_DYNAMIC_MINOR,
+};
+
+static int __init mshv_vtl_init(void)
+{
+ int ret;
+ struct device *dev = mshv_dev.this_device;
+
+ /*
+ * This creates /dev/mshv which provides functionality to create VTLs and partitions.
+ */
+ ret = misc_register(&mshv_dev);
+ if (ret) {
+ dev_err(dev, "mshv device register failed: %d\n", ret);
+ goto free_dev;
+ }
+
+ tasklet_init(&msg_dpc, mshv_vtl_sint_on_msg_dpc, 0);
+ init_waitqueue_head(&fd_wait_queue);
+
+ if (mshv_vtl_get_vsm_regs()) {
+ dev_emerg(dev, "Unable to get VSM capabilities !!\n");
+ ret = -ENODEV;
+ goto free_dev;
+ }
+ if (mshv_vtl_configure_vsm_partition(dev)) {
+ dev_emerg(dev, "VSM configuration failed !!\n");
+ ret = -ENODEV;
+ goto free_dev;
+ }
+
+ mshv_vtl_return_call_init(mshv_vsm_page_offsets.vtl_return_offset);
+ ret = hv_vtl_setup_synic();
+ if (ret)
+ goto free_dev;
+
+ /*
+ * mshv_sint device adds VMBus relay ioctl support.
+ * This provides a channel for VTL0 to communicate with VTL2.
+ */
+ ret = misc_register(&mshv_vtl_sint_dev);
+ if (ret)
+ goto free_synic;
+
+ /*
+ * mshv_hvcall device adds interface to enable userspace for direct hypercalls support.
+ */
+ ret = misc_register(&mshv_vtl_hvcall_dev);
+ if (ret)
+ goto free_sint;
+
+ /*
+ * mshv_vtl_low device is used to map VTL0 address space to a user-mode process in VTL2.
+ * It implements mmap() to allow a user-mode process in VTL2 to map to the address of VTL0.
+ */
+ ret = misc_register(&mshv_vtl_low);
+ if (ret)
+ goto free_hvcall;
+
+ /*
+ * "mshv vtl mem dev" device is later used to setup VTL0 memory.
+ */
+ mem_dev = kzalloc(sizeof(*mem_dev), GFP_KERNEL);
+ if (!mem_dev) {
+ ret = -ENOMEM;
+ goto free_low;
+ }
+
+ mutex_init(&mshv_vtl_poll_file_lock);
+
+ device_initialize(mem_dev);
+ dev_set_name(mem_dev, "mshv vtl mem dev");
+ ret = device_add(mem_dev);
+ if (ret) {
+ dev_err(dev, "mshv vtl mem dev add: %d\n", ret);
+ goto free_mem;
+ }
+
+ return 0;
+
+free_mem:
+ kfree(mem_dev);
+free_low:
+ misc_deregister(&mshv_vtl_low);
+free_hvcall:
+ misc_deregister(&mshv_vtl_hvcall_dev);
+free_sint:
+ misc_deregister(&mshv_vtl_sint_dev);
+free_synic:
+ hv_vtl_remove_synic();
+free_dev:
+ misc_deregister(&mshv_dev);
+
+ return ret;
+}
+
+static void __exit mshv_vtl_exit(void)
+{
+ device_del(mem_dev);
+ kfree(mem_dev);
+ misc_deregister(&mshv_vtl_low);
+ misc_deregister(&mshv_vtl_hvcall_dev);
+ misc_deregister(&mshv_vtl_sint_dev);
+ hv_vtl_remove_synic();
+ misc_deregister(&mshv_dev);
+}
+
+module_init(mshv_vtl_init);
+module_exit(mshv_vtl_exit);
diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
index f6e31d1c3267..307ff8ed5aff 100644
--- a/include/hyperv/hvgdk_mini.h
+++ b/include/hyperv/hvgdk_mini.h
@@ -883,6 +883,48 @@ struct hv_get_vp_from_apic_id_in {
u32 apic_ids[];
} __packed;
+union hv_register_vsm_partition_config {
+ u64 as_uint64;
+ struct {
+ u64 enable_vtl_protection : 1;
+ u64 default_vtl_protection_mask : 4;
+ u64 zero_memory_on_reset : 1;
+ u64 deny_lower_vtl_startup : 1;
+ u64 intercept_acceptance : 1;
+ u64 intercept_enable_vtl_protection : 1;
+ u64 intercept_vp_startup : 1;
+ u64 intercept_cpuid_unimplemented : 1;
+ u64 intercept_unrecoverable_exception : 1;
+ u64 intercept_page : 1;
+ u64 mbz : 51;
+ } __packed;
+};
+
+union hv_register_vsm_capabilities {
+ u64 as_uint64;
+ struct {
+ u64 dr6_shared: 1;
+ u64 mbec_vtl_mask: 16;
+ u64 deny_lower_vtl_startup: 1;
+ u64 supervisor_shadow_stack: 1;
+ u64 hardware_hvpt_available: 1;
+ u64 software_hvpt_available: 1;
+ u64 hardware_hvpt_range_bits: 6;
+ u64 intercept_page_available: 1;
+ u64 return_action_available: 1;
+ u64 reserved: 35;
+ } __packed;
+};
+
+union hv_register_vsm_page_offsets {
+ struct {
+ u64 vtl_call_offset : 12;
+ u64 vtl_return_offset : 12;
+ u64 reserved_mbz : 40;
+ } __packed;
+ u64 as_uint64;
+};
+
struct hv_nested_enlightenments_control {
struct {
u32 directhypercall : 1;
@@ -1005,6 +1047,70 @@ enum hv_register_name {
/* VSM */
HV_REGISTER_VSM_VP_STATUS = 0x000D0003,
+
+ /* Synthetic VSM registers */
+ HV_REGISTER_VSM_CODE_PAGE_OFFSETS = 0x000D0002,
+ HV_REGISTER_VSM_CAPABILITIES = 0x000D0006,
+ HV_REGISTER_VSM_PARTITION_CONFIG = 0x000D0007,
+
+#if defined(CONFIG_X86)
+ /* X64 Debug Registers */
+ HV_X64_REGISTER_DR0 = 0x00050000,
+ HV_X64_REGISTER_DR1 = 0x00050001,
+ HV_X64_REGISTER_DR2 = 0x00050002,
+ HV_X64_REGISTER_DR3 = 0x00050003,
+ HV_X64_REGISTER_DR6 = 0x00050004,
+ HV_X64_REGISTER_DR7 = 0x00050005,
+
+ /* X64 Cache control MSRs */
+ HV_X64_REGISTER_MSR_MTRR_CAP = 0x0008000D,
+ HV_X64_REGISTER_MSR_MTRR_DEF_TYPE = 0x0008000E,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE0 = 0x00080010,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE1 = 0x00080011,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE2 = 0x00080012,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE3 = 0x00080013,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE4 = 0x00080014,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE5 = 0x00080015,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE6 = 0x00080016,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE7 = 0x00080017,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE8 = 0x00080018,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASE9 = 0x00080019,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASEA = 0x0008001A,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASEB = 0x0008001B,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASEC = 0x0008001C,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASED = 0x0008001D,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASEE = 0x0008001E,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_BASEF = 0x0008001F,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK0 = 0x00080040,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK1 = 0x00080041,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK2 = 0x00080042,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK3 = 0x00080043,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK4 = 0x00080044,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK5 = 0x00080045,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK6 = 0x00080046,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK7 = 0x00080047,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK8 = 0x00080048,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASK9 = 0x00080049,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASKA = 0x0008004A,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASKB = 0x0008004B,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASKC = 0x0008004C,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASKD = 0x0008004D,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASKE = 0x0008004E,
+ HV_X64_REGISTER_MSR_MTRR_PHYS_MASKF = 0x0008004F,
+ HV_X64_REGISTER_MSR_MTRR_FIX64K00000 = 0x00080070,
+ HV_X64_REGISTER_MSR_MTRR_FIX16K80000 = 0x00080071,
+ HV_X64_REGISTER_MSR_MTRR_FIX16KA0000 = 0x00080072,
+ HV_X64_REGISTER_MSR_MTRR_FIX4KC0000 = 0x00080073,
+ HV_X64_REGISTER_MSR_MTRR_FIX4KC8000 = 0x00080074,
+ HV_X64_REGISTER_MSR_MTRR_FIX4KD0000 = 0x00080075,
+ HV_X64_REGISTER_MSR_MTRR_FIX4KD8000 = 0x00080076,
+ HV_X64_REGISTER_MSR_MTRR_FIX4KE0000 = 0x00080077,
+ HV_X64_REGISTER_MSR_MTRR_FIX4KE8000 = 0x00080078,
+ HV_X64_REGISTER_MSR_MTRR_FIX4KF0000 = 0x00080079,
+ HV_X64_REGISTER_MSR_MTRR_FIX4KF8000 = 0x0008007A,
+
+ HV_X64_REGISTER_REG_PAGE = 0x0009001C,
+#endif
};
/*
diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h
index 876bfe4e4227..ee10e21e1a11 100644
--- a/include/uapi/linux/mshv.h
+++ b/include/uapi/linux/mshv.h
@@ -288,4 +288,84 @@ struct mshv_get_set_vp_state {
* #define MSHV_ROOT_HVCALL _IOWR(MSHV_IOCTL, 0x07, struct mshv_root_hvcall)
*/
+/* Structure definitions, macros and IOCTLs for mshv_vtl */
+
+#define MSHV_CAP_CORE_API_STABLE 0x0
+#define MSHV_CAP_REGISTER_PAGE 0x1
+#define MSHV_CAP_VTL_RETURN_ACTION 0x2
+#define MSHV_CAP_DR6_SHARED 0x3
+#define MSHV_MAX_RUN_MSG_SIZE 256
+
+struct mshv_vp_registers {
+ __u32 count; /* supports only 1 register at a time */
+ __u32 reserved; /* Reserved for alignment or future use */
+ __u64 regs_ptr; /* pointer to struct hv_register_assoc */
+};
+
+struct mshv_vtl_set_eventfd {
+ __s32 fd;
+ __u32 flag;
+};
+
+struct mshv_vtl_signal_event {
+ __u32 connection_id;
+ __u32 flag;
+};
+
+struct mshv_vtl_sint_post_msg {
+ __u64 message_type;
+ __u32 connection_id;
+ __u32 payload_size; /* Must not exceed HV_MESSAGE_PAYLOAD_BYTE_COUNT */
+ __u64 payload_ptr; /* pointer to message payload (bytes) */
+};
+
+struct mshv_vtl_ram_disposition {
+ __u64 start_pfn;
+ __u64 last_pfn;
+};
+
+struct mshv_vtl_set_poll_file {
+ __u32 cpu;
+ __u32 fd;
+};
+
+struct mshv_vtl_hvcall_setup {
+ __u64 bitmap_array_size; /* stores number of bytes */
+ __u64 allow_bitmap_ptr;
+};
+
+struct mshv_vtl_hvcall {
+ __u64 control; /* Hypercall control code */
+ __u64 input_size; /* Size of the input data */
+ __u64 input_ptr; /* Pointer to the input struct */
+ __u64 status; /* Status of the hypercall (output) */
+ __u64 output_size; /* Size of the output data */
+ __u64 output_ptr; /* Pointer to the output struct */
+};
+
+struct mshv_sint_mask {
+ __u8 mask;
+ __u8 reserved[7];
+};
+
+/* /dev/mshv device IOCTL */
+#define MSHV_CHECK_EXTENSION _IOW(MSHV_IOCTL, 0x00, __u32)
+
+/* vtl device */
+#define MSHV_CREATE_VTL _IOR(MSHV_IOCTL, 0x1D, char)
+#define MSHV_ADD_VTL0_MEMORY _IOW(MSHV_IOCTL, 0x21, struct mshv_vtl_ram_disposition)
+#define MSHV_SET_POLL_FILE _IOW(MSHV_IOCTL, 0x25, struct mshv_vtl_set_poll_file)
+#define MSHV_RETURN_TO_LOWER_VTL _IO(MSHV_IOCTL, 0x27)
+#define MSHV_GET_VP_REGISTERS _IOWR(MSHV_IOCTL, 0x05, struct mshv_vp_registers)
+#define MSHV_SET_VP_REGISTERS _IOW(MSHV_IOCTL, 0x06, struct mshv_vp_registers)
+
+/* VMBus device IOCTLs */
+#define MSHV_SINT_SIGNAL_EVENT _IOW(MSHV_IOCTL, 0x22, struct mshv_vtl_signal_event)
+#define MSHV_SINT_POST_MESSAGE _IOW(MSHV_IOCTL, 0x23, struct mshv_vtl_sint_post_msg)
+#define MSHV_SINT_SET_EVENTFD _IOW(MSHV_IOCTL, 0x24, struct mshv_vtl_set_eventfd)
+#define MSHV_SINT_PAUSE_MESSAGE_STREAM _IOW(MSHV_IOCTL, 0x25, struct mshv_sint_mask)
+
+/* hv_hvcall device */
+#define MSHV_HVCALL_SETUP _IOW(MSHV_IOCTL, 0x1E, struct mshv_vtl_hvcall_setup)
+#define MSHV_HVCALL _IOWR(MSHV_IOCTL, 0x1F, struct mshv_vtl_hvcall)
#endif
--
2.43.0
^ permalink raw reply related
* Re: [PATCH v6 01/10] x86/acpi: Add helper functions to setup and access the wakeup mailbox
From: Rafael J. Wysocki @ 2025-10-17 9:46 UTC (permalink / raw)
To: Ricardo Neri
Cc: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Rafael J. Wysocki, Saurabh Sengar, Chris Oo,
Kirill A. Shutemov, linux-hyperv, devicetree, linux-acpi,
linux-kernel, Ricardo Neri, Rafael J. Wysocki
In-Reply-To: <20251016-rneri-wakeup-mailbox-v6-1-40435fb9305e@linux.intel.com>
On Fri, Oct 17, 2025 at 4:48 AM Ricardo Neri
<ricardo.neri-calderon@linux.intel.com> wrote:
>
> In preparation to move the functionality to wake secondary CPUs up from the
> ACPI code, add two helper functions.
>
> The function acpi_setup_mp_wakeup_mailbox() stores the physical address of
> the mailbox and updates the wakeup_secondary_cpu_64() APIC callback.
>
> There is a slight change in behavior: now the APIC callback is updated
> before configuring CPU hotplug offline behavior. This is fine as the APIC
> callback continues to be updated unconditionally, regardless of the
> restriction on CPU offlining.
>
> The function acpi_madt_multiproc_wakeup_mailbox() returns a pointer to the
> mailbox. Use this helper function only in the portions of the code for
> which the variable acpi_mp_wake_mailbox will be out of scope once it is
> relocated out of the ACPI directory.
>
> The wakeup mailbox is only supported for CONFIG_X86_64 and needed only with
> CONFIG_SMP=y.
>
> Reviewed-by: Dexuan Cui <decui@microsoft.com>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This should have been
Acked-by: Rafael J. Wysocki (Intel) <rafael.j.wysocki@intel.com>
The "(Intel)" part is missing and I omitted it when I sent the tag.
Sorry for the confusion.
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> ---
> Changes since v5:
> - Fixed grammar error in the subject of the patch. (Rafael)
> - Added Acked-by tag from Rafael. Thanks!
> - Added Reviewed-by tag from Dexuan. Thanks!
>
> Changes since v4:
> - None
>
> Changes since v3:
> - Squashed the two first patches of the series into one, both introduce
> helper functions. (Rafael)
> - Renamed setup_mp_wakeup_mailbox() as acpi_setup_mp_wakeup_mailbox().
> (Rafael)
> - Dropped the function prototype for !CONFIG_X86_64. (Rafael)
>
> Changes since v2:
> - Introduced this patch.
>
> Changes since v1:
> - N/A
> ---
> arch/x86/include/asm/smp.h | 3 +++
> arch/x86/kernel/acpi/madt_wakeup.c | 20 +++++++++++++++-----
> 2 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 22bfebe6776d..47ac4381a805 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -149,6 +149,9 @@ static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
> return per_cpu(cpu_l2c_shared_map, cpu);
> }
>
> +void acpi_setup_mp_wakeup_mailbox(u64 addr);
> +struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void);
> +
> #else /* !CONFIG_SMP */
> #define wbinvd_on_cpu(cpu) wbinvd()
> static inline void wbinvd_on_all_cpus(void)
> diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
> index 6d7603511f52..c3ac5ecf3e7d 100644
> --- a/arch/x86/kernel/acpi/madt_wakeup.c
> +++ b/arch/x86/kernel/acpi/madt_wakeup.c
> @@ -37,6 +37,7 @@ static void acpi_mp_play_dead(void)
>
> static void acpi_mp_cpu_die(unsigned int cpu)
> {
> + struct acpi_madt_multiproc_wakeup_mailbox *mailbox = acpi_get_mp_wakeup_mailbox();
> u32 apicid = per_cpu(x86_cpu_to_apicid, cpu);
> unsigned long timeout;
>
> @@ -46,13 +47,13 @@ static void acpi_mp_cpu_die(unsigned int cpu)
> *
> * BIOS has to clear 'command' field of the mailbox.
> */
> - acpi_mp_wake_mailbox->apic_id = apicid;
> - smp_store_release(&acpi_mp_wake_mailbox->command,
> + mailbox->apic_id = apicid;
> + smp_store_release(&mailbox->command,
> ACPI_MP_WAKE_COMMAND_TEST);
>
> /* Don't wait longer than a second. */
> timeout = USEC_PER_SEC;
> - while (READ_ONCE(acpi_mp_wake_mailbox->command) && --timeout)
> + while (READ_ONCE(mailbox->command) && --timeout)
> udelay(1);
>
> if (!timeout)
> @@ -227,7 +228,7 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
>
> acpi_table_print_madt_entry(&header->common);
>
> - acpi_mp_wake_mailbox_paddr = mp_wake->mailbox_address;
> + acpi_setup_mp_wakeup_mailbox(mp_wake->mailbox_address);
>
> if (mp_wake->version >= ACPI_MADT_MP_WAKEUP_VERSION_V1 &&
> mp_wake->header.length >= ACPI_MADT_MP_WAKEUP_SIZE_V1) {
> @@ -243,7 +244,16 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
> acpi_mp_disable_offlining(mp_wake);
> }
>
> + return 0;
> +}
> +
> +void __init acpi_setup_mp_wakeup_mailbox(u64 mailbox_paddr)
> +{
> + acpi_mp_wake_mailbox_paddr = mailbox_paddr;
> apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
> +}
>
> - return 0;
> +struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
> +{
> + return acpi_mp_wake_mailbox;
> }
>
> --
> 2.43.0
>
^ permalink raw reply
* Re: [PATCH] mshv: Fix deposit memory in MSHV_ROOT_HVCALL
From: Nuno Das Neves @ 2025-10-17 17:25 UTC (permalink / raw)
To: Michael Kelley, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, arnd@arndb.de, mrathor@linux.microsoft.com,
skinsburskii@linux.microsoft.com
In-Reply-To: <SN6PR02MB4157E6D02773A9D7A4B9E85BD4F6A@SN6PR02MB4157.namprd02.prod.outlook.com>
On 10/16/2025 6:12 PM, Michael Kelley wrote:
> From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Thursday, October 16, 2025 12:54 PM
>>
>> When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
>> HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
>> -EAGAIN to userspace.
>>
>> However, it's much easier and efficient if the driver simply deposits
>> memory on demand and immediately retries the hypercall as is done with
>> all the other hypercall helper functions.
>>
>> But unlike those, in MSHV_ROOT_HVCALL the input is opaque to the
>> kernel. This is problematic for rep hypercalls, because the next part
>> of the input list can't be copied on each loop after depositing pages
>> (this was the original reason for returning -EAGAIN in this case).
>>
>> Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
>> parameter. This solves the issue, allowing the deposit loop in
>> MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
>> partway through.
>
>>From reading the above, I'm pretty sure this code change is an
> optimization that lets user space avoid having to deal with the
> -EAGAIN result by resubmitting the ioctl with a different
> starting point for a rep hypercall. As such, I'd suggest the patch
> title should be "Improve deposit memory ...." (or something similar).
> The word "Fix" makes it sound like a bug fix.
>
> Or is user space code currently faulty in its handling of -EAGAIN, and
> this really is an indirect bug fix to make things work? If so, do you
> want a Fixes: tag so the change is backported?
>
It's the latter case, userspace doesn't handle it correctly, so I
consider it a fix more than just an improvement.
I'll add a Fixes: tag pointing back to the original /dev/mshv patch.
>>
>> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
>> ---
>> drivers/hv/mshv_root_main.c | 52 ++++++++++++++++++++--------------
>> include/asm-generic/mshyperv.h | 14 +++++++--
>> 2 files changed, 42 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
>> index 9ae67c6e9f60..731ec8cbbd63 100644
>> --- a/drivers/hv/mshv_root_main.c
>> +++ b/drivers/hv/mshv_root_main.c
>> @@ -159,6 +159,7 @@ static int mshv_ioctl_passthru_hvcall(struct mshv_partition *partition,
>> unsigned int pages_order;
>> void *input_pg = NULL;
>> void *output_pg = NULL;
>> + u16 reps_completed;
>>
>> if (copy_from_user(&args, user_args, sizeof(args)))
>> return -EFAULT;
>> @@ -210,28 +211,35 @@ static int mshv_ioctl_passthru_hvcall(struct mshv_partition *partition,
>> */
>> *(u64 *)input_pg = partition->pt_id;
>>
>> - if (args.reps)
>> - status = hv_do_rep_hypercall(args.code, args.reps, 0,
>> - input_pg, output_pg);
>> - else
>> - status = hv_do_hypercall(args.code, input_pg, output_pg);
>> -
>> - if (hv_result(status) == HV_STATUS_CALL_PENDING) {
>> - if (is_async) {
>> - mshv_async_hvcall_handler(partition, &status);
>> - } else { /* Paranoia check. This shouldn't happen! */
>> - ret = -EBADFD;
>> - goto free_pages_out;
>> + reps_completed = 0;
>> + do {
>> + if (args.reps) {
>> + status = hv_do_rep_hypercall_ex(args.code, args.reps,
>> + 0, reps_completed,
>> + input_pg, output_pg);
>> + reps_completed = hv_repcomp(status);
>> + } else {
>> + status = hv_do_hypercall(args.code, input_pg, output_pg);
>> }
>> - }
>>
>> - if (hv_result(status) == HV_STATUS_INSUFFICIENT_MEMORY) {
>> - ret = hv_call_deposit_pages(NUMA_NO_NODE, partition->pt_id, 1);
>> - if (!ret)
>> - ret = -EAGAIN;
>> - } else if (!hv_result_success(status)) {
>> - ret = hv_result_to_errno(status);
>> - }
>> + if (hv_result(status) == HV_STATUS_CALL_PENDING) {
>> + if (is_async) {
>> + mshv_async_hvcall_handler(partition, &status);
>> + } else { /* Paranoia check. This shouldn't happen! */
>> + ret = -EBADFD;
>> + goto free_pages_out;
>> + }
>> + }
>> +
>> + if (hv_result_success(status))
>> + break;
>> +
>> + if (hv_result(status) != HV_STATUS_INSUFFICIENT_MEMORY)
>> + ret = hv_result_to_errno(status);
>> + else
>> + ret = hv_call_deposit_pages(NUMA_NO_NODE,
>> + partition->pt_id, 1);
>> + } while (!ret);
>>
>> /*
>> * Always return the status and output data regardless of result.
>
> This comment about always returning the output data is now incorrect.
>
Thanks, I'll fix it
>> @@ -240,11 +248,11 @@ static int mshv_ioctl_passthru_hvcall(struct mshv_partition *partition,
>> * succeeded.
>> */
>> args.status = hv_result(status);
>> - args.reps = args.reps ? hv_repcomp(status) : 0;
>> + args.reps = reps_completed;
>> if (copy_to_user(user_args, &args, sizeof(args)))
>> ret = -EFAULT;
>>
>> - if (output_pg &&
>> + if (!ret && output_pg &&
>> copy_to_user((void __user *)args.out_ptr, output_pg, args.out_sz))
>> ret = -EFAULT;
>>
>> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
>> index ebf458dbcf84..31a209f0e18f 100644
>> --- a/include/asm-generic/mshyperv.h
>> +++ b/include/asm-generic/mshyperv.h
>> @@ -128,8 +128,9 @@ static inline unsigned int hv_repcomp(u64 status)
>> * Rep hypercalls. Callers of this functions are supposed to ensure that
>> * rep_count and varhead_size comply with Hyper-V hypercall definition.
>
> Nit: This comment could be updated to include the new "rep_start"
> parameter.
>
Thanks, will add
>> */
>> -static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
>> - void *input, void *output)
>> +static inline u64 hv_do_rep_hypercall_ex(u16 code, u16 rep_count,
>> + u16 varhead_size, u16 rep_start,
>> + void *input, void *output)
>> {
>> u64 control = code;
>> u64 status;
>> @@ -137,6 +138,7 @@ static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
>>
>> control |= (u64)varhead_size << HV_HYPERCALL_VARHEAD_OFFSET;
>> control |= (u64)rep_count << HV_HYPERCALL_REP_COMP_OFFSET;
>> + control |= (u64)rep_start << HV_HYPERCALL_REP_START_OFFSET;
>>
>> do {
>> status = hv_do_hypercall(control, input, output);
>> @@ -154,6 +156,14 @@ static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
>> return status;
>> }
>>
>> +/* For the typical case where rep_start is 0 */
>> +static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
>> + void *input, void *output)
>> +{
>> + return hv_do_rep_hypercall_ex(code, rep_count, varhead_size, 0,
>> + input, output);
>> +}
>> +
>> /* Generate the guest OS identifier as described in the Hyper-V TLFS */
>> static inline u64 hv_generate_guest_id(u64 kernel_version)
>> {
>
> Overall, this looks good to me. I don't see any issues with the code.
>
> Michael
^ permalink raw reply
* RE: [PATCH] mshv: Fix deposit memory in MSHV_ROOT_HVCALL
From: Michael Kelley @ 2025-10-17 17:33 UTC (permalink / raw)
To: Nuno Das Neves, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, arnd@arndb.de, mrathor@linux.microsoft.com,
skinsburskii@linux.microsoft.com
In-Reply-To: <a0090bbf-08b4-4b36-8cf2-18687a83ee8f@linux.microsoft.com>
From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Friday, October 17, 2025 10:26 AM
>
> On 10/16/2025 6:12 PM, Michael Kelley wrote:
> > From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Thursday, October 16, 2025 12:54 PM
> >>
> >> When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
> >> HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
> >> -EAGAIN to userspace.
> >>
> >> However, it's much easier and efficient if the driver simply deposits
> >> memory on demand and immediately retries the hypercall as is done with
> >> all the other hypercall helper functions.
> >>
> >> But unlike those, in MSHV_ROOT_HVCALL the input is opaque to the
> >> kernel. This is problematic for rep hypercalls, because the next part
> >> of the input list can't be copied on each loop after depositing pages
> >> (this was the original reason for returning -EAGAIN in this case).
> >>
> >> Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
> >> parameter. This solves the issue, allowing the deposit loop in
> >> MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
> >> partway through.
> >
> >>From reading the above, I'm pretty sure this code change is an
> > optimization that lets user space avoid having to deal with the
> > -EAGAIN result by resubmitting the ioctl with a different
> > starting point for a rep hypercall. As such, I'd suggest the patch
> > title should be "Improve deposit memory ...." (or something similar).
> > The word "Fix" makes it sound like a bug fix.
> >
> > Or is user space code currently faulty in its handling of -EAGAIN, and
> > this really is an indirect bug fix to make things work? If so, do you
> > want a Fixes: tag so the change is backported?
> >
>
> It's the latter case, userspace doesn't handle it correctly, so I
> consider it a fix more than just an improvement.
OK, thanks. You might want to tweak the commit message a bit
to clarify that this really is a bug fix and why. I was leaning
toward the wrong conclusion based on the current commit
message.
Michael
>
> I'll add a Fixes: tag pointing back to the original /dev/mshv patch.
>
^ permalink raw reply
* Re: [PATCH net-next] net: mana: Linearize SKB if TX SGEs exceeds hardware limit
From: Aditya Garg @ 2025-10-17 17:41 UTC (permalink / raw)
To: Eric Dumazet
Cc: kys, haiyangz, wei.liu, decui, andrew+netdev, davem, kuba, pabeni,
longli, kotaranov, horms, shradhagupta, ernis, dipayanroy,
shirazsaleem, linux-hyperv, netdev, linux-kernel, linux-rdma,
gargaditya, ssengar
In-Reply-To: <7bc327ba-0050-4d9e-86b6-1b7427a96f53@linux.microsoft.com>
On 08-10-2025 20:58, Aditya Garg wrote:
> On 08-10-2025 20:51, Eric Dumazet wrote:
>> On Wed, Oct 8, 2025 at 8:16 AM Aditya Garg
>> <gargaditya@linux.microsoft.com> wrote:
>>>
>>> On 03-10-2025 21:45, Eric Dumazet wrote:
>>>> On Fri, Oct 3, 2025 at 8:47 AM Aditya Garg
>>>> <gargaditya@linux.microsoft.com> wrote:
>>>>>
>>>>> The MANA hardware supports a maximum of 30 scatter-gather entries
>>>>> (SGEs)
>>>>> per TX WQE. In rare configurations where MAX_SKB_FRAGS + 2 exceeds
>>>>> this
>>>>> limit, the driver drops the skb. Add a check in mana_start_xmit() to
>>>>> detect such cases and linearize the SKB before transmission.
>>>>>
>>>>> Return NETDEV_TX_BUSY only for -ENOSPC from
>>>>> mana_gd_post_work_request(),
>>>>> send other errors to free_sgl_ptr to free resources and record the tx
>>>>> drop.
>>>>>
>>>>> Signed-off-by: Aditya Garg <gargaditya@linux.microsoft.com>
>>>>> Reviewed-by: Dipayaan Roy <dipayanroy@linux.microsoft.com>
>>>>> ---
>>>>> drivers/net/ethernet/microsoft/mana/mana_en.c | 26 +++++++++++++
>>>>> ++----
>>>>> include/net/mana/gdma.h | 8 +++++-
>>>>> include/net/mana/mana.h | 1 +
>>>>> 3 files changed, 29 insertions(+), 6 deletions(-)
>>>>>
>>>>> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/
>>>>> drivers/net/ethernet/microsoft/mana/mana_en.c
>>>>> index f4fc86f20213..22605753ca84 100644
>>>>> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
>>>>> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
>>>>> @@ -20,6 +20,7 @@
>>>>>
>>>>> #include <net/mana/mana.h>
>>>>> #include <net/mana/mana_auxiliary.h>
>>>>> +#include <linux/skbuff.h>
>>>>>
>>>>> static DEFINE_IDA(mana_adev_ida);
>>>>>
>>>>> @@ -289,6 +290,19 @@ netdev_tx_t mana_start_xmit(struct sk_buff
>>>>> *skb, struct net_device *ndev)
>>>>> cq = &apc->tx_qp[txq_idx].tx_cq;
>>>>> tx_stats = &txq->stats;
>>>>>
>>>>> + BUILD_BUG_ON(MAX_TX_WQE_SGL_ENTRIES !=
>>>>> MANA_MAX_TX_WQE_SGL_ENTRIES);
>>>>> + #if (MAX_SKB_FRAGS + 2 > MANA_MAX_TX_WQE_SGL_ENTRIES)
>>>>> + if (skb_shinfo(skb)->nr_frags + 2 >
>>>>> MANA_MAX_TX_WQE_SGL_ENTRIES) {
>>>>> + netdev_info_once(ndev,
>>>>> + "nr_frags %d exceeds max
>>>>> supported sge limit. Attempting skb_linearize\n",
>>>>> + skb_shinfo(skb)->nr_frags);
>>>>> + if (skb_linearize(skb)) {
>>>>
>>>> This will fail in many cases.
>>>>
>>>> This sort of check is better done in ndo_features_check()
>>>>
>>>> Most probably this would occur for GSO packets, so can ask a software
>>>> segmentation
>>>> to avoid this big and risky kmalloc() by all means.
>>>>
>>>> Look at idpf_features_check() which has something similar.
>>>
>>> Hi Eric,
>>> Thank you for your review. I understand your concerns regarding the use
>>> of skb_linearize() in the xmit path, as it can fail under memory
>>> pressure and introduces additional overhead in the transmit path. Based
>>> on your input, I will work on a v2 that will move the SGE limit check to
>>> the ndo_features_check() path and for GSO skbs exceding the hw limit
>>> will disable the NETIF_F_GSO_MASK to enforce software segmentation in
>>> kernel before the call to xmit.
>>> Also for non GSO skb exceeding the SGE hw limit should we go for using
>>> skb_linearize only then or would you suggest some other approach here?
>>
>> I think that for non GSO, the linearization attempt is fine.
>>
>> Note that this is extremely unlikely for non malicious users,
>> and MTU being usually small (9K or less),
>> the allocation will be much smaller than a GSO packet.
>
> Okay. Will send a v2
Hi Eric,
I tested the code by disabling GSO in ndo_features_check when the number
of SGEs exceeds the hardware limit, using iperf for a single TCP
connection with zerocopy enabled. I noticed a significant difference in
throughput compared to when we linearize the skbs.
For reference, the throughput is 35.6 Gbits/sec when using
skb_linearize, but drops to 6.75 Gbits/sec when disabling GSO per skb.
Hence, We propose to linearizing skbs until the first failure occurs.
After that, we switch to a fail-safe mode by disabling GSO for SKBs with
sge > hw limit using the ndo_feature_check implementation, while
continuing to apply skb_linearize() for non-GSO packets that exceed the
hardware limit. This ensures we remain on the optimal performance path
initially, and only transition to the fail-safe path after encountering
a failure.
Regards,
Aditya
^ permalink raw reply
* Re: [PATCH] mshv: Fix deposit memory in MSHV_ROOT_HVCALL
From: Nuno Das Neves @ 2025-10-17 17:55 UTC (permalink / raw)
To: Michael Kelley, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, arnd@arndb.de, mrathor@linux.microsoft.com,
skinsburskii@linux.microsoft.com
In-Reply-To: <SN6PR02MB4157EE75A14F5F7EA7D6D070D4F6A@SN6PR02MB4157.namprd02.prod.outlook.com>
On 10/17/2025 10:33 AM, Michael Kelley wrote:
> From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Friday, October 17, 2025 10:26 AM
>>
>> On 10/16/2025 6:12 PM, Michael Kelley wrote:
>>> From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Thursday, October 16, 2025 12:54 PM
>>>>
>>>> When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
>>>> HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
>>>> -EAGAIN to userspace.
>>>>
>>>> However, it's much easier and efficient if the driver simply deposits
>>>> memory on demand and immediately retries the hypercall as is done with
>>>> all the other hypercall helper functions.
>>>>
>>>> But unlike those, in MSHV_ROOT_HVCALL the input is opaque to the
>>>> kernel. This is problematic for rep hypercalls, because the next part
>>>> of the input list can't be copied on each loop after depositing pages
>>>> (this was the original reason for returning -EAGAIN in this case).
>>>>
>>>> Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
>>>> parameter. This solves the issue, allowing the deposit loop in
>>>> MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
>>>> partway through.
>>>
>>> >From reading the above, I'm pretty sure this code change is an
>>> optimization that lets user space avoid having to deal with the
>>> -EAGAIN result by resubmitting the ioctl with a different
>>> starting point for a rep hypercall. As such, I'd suggest the patch
>>> title should be "Improve deposit memory ...." (or something similar).
>>> The word "Fix" makes it sound like a bug fix.
>>>
>>> Or is user space code currently faulty in its handling of -EAGAIN, and
>>> this really is an indirect bug fix to make things work? If so, do you
>>> want a Fixes: tag so the change is backported?
>>>
>>
>> It's the latter case, userspace doesn't handle it correctly, so I
>> consider it a fix more than just an improvement.
>
> OK, thanks. You might want to tweak the commit message a bit
> to clarify that this really is a bug fix and why. I was leaning
> toward the wrong conclusion based on the current commit
> message.
>
Is this clearer?
"
mshv: Fix deposit memory in MSHV_ROOT_HVCALL
When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
-EAGAIN to userspace. The expectation is that the VMM will retry.
However, some VMM code in the wild doesn't do this and simply fails.
Rather than force the VMM to retry, change the ioctl to deposit
memory on demand and immediately retry the hypercall as is done with
all the other hypercall helper functions.
In addition to making the ioctl easier to use, removing the need for
multiple syscalls improves performance.
There is a complication: unlike the other hypercall helper functions,
in MSHV_ROOT_HVCALL the input is opaque to the kernel. This is
problematic for rep hypercalls, because the next part of the input
list can't be copied on each loop after depositing pages (this was
the original reason for returning -EAGAIN in this case).
Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
parameter. This solves the issue, allowing the deposit loop in
MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
partway through.
"
> Michael
>
>>
>> I'll add a Fixes: tag pointing back to the original /dev/mshv patch.
>>
^ permalink raw reply
* Re: [PATCH net-next] net: mana: Linearize SKB if TX SGEs exceeds hardware limit
From: Eric Dumazet @ 2025-10-17 18:06 UTC (permalink / raw)
To: Aditya Garg
Cc: kys, haiyangz, wei.liu, decui, andrew+netdev, davem, kuba, pabeni,
longli, kotaranov, horms, shradhagupta, ernis, dipayanroy,
shirazsaleem, linux-hyperv, netdev, linux-kernel, linux-rdma,
gargaditya, ssengar
In-Reply-To: <1d3ac973-7bc7-4abe-9fe2-6b17dbba223b@linux.microsoft.com>
On Fri, Oct 17, 2025 at 10:41 AM Aditya Garg
<gargaditya@linux.microsoft.com> wrote:
>
> On 08-10-2025 20:58, Aditya Garg wrote:
> > On 08-10-2025 20:51, Eric Dumazet wrote:
> >> On Wed, Oct 8, 2025 at 8:16 AM Aditya Garg
> >> <gargaditya@linux.microsoft.com> wrote:
> >>>
> >>> On 03-10-2025 21:45, Eric Dumazet wrote:
> >>>> On Fri, Oct 3, 2025 at 8:47 AM Aditya Garg
> >>>> <gargaditya@linux.microsoft.com> wrote:
> >>>>>
> >>>>> The MANA hardware supports a maximum of 30 scatter-gather entries
> >>>>> (SGEs)
> >>>>> per TX WQE. In rare configurations where MAX_SKB_FRAGS + 2 exceeds
> >>>>> this
> >>>>> limit, the driver drops the skb. Add a check in mana_start_xmit() to
> >>>>> detect such cases and linearize the SKB before transmission.
> >>>>>
> >>>>> Return NETDEV_TX_BUSY only for -ENOSPC from
> >>>>> mana_gd_post_work_request(),
> >>>>> send other errors to free_sgl_ptr to free resources and record the tx
> >>>>> drop.
> >>>>>
> >>>>> Signed-off-by: Aditya Garg <gargaditya@linux.microsoft.com>
> >>>>> Reviewed-by: Dipayaan Roy <dipayanroy@linux.microsoft.com>
> >>>>> ---
> >>>>> drivers/net/ethernet/microsoft/mana/mana_en.c | 26 +++++++++++++
> >>>>> ++----
> >>>>> include/net/mana/gdma.h | 8 +++++-
> >>>>> include/net/mana/mana.h | 1 +
> >>>>> 3 files changed, 29 insertions(+), 6 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/
> >>>>> drivers/net/ethernet/microsoft/mana/mana_en.c
> >>>>> index f4fc86f20213..22605753ca84 100644
> >>>>> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> >>>>> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> >>>>> @@ -20,6 +20,7 @@
> >>>>>
> >>>>> #include <net/mana/mana.h>
> >>>>> #include <net/mana/mana_auxiliary.h>
> >>>>> +#include <linux/skbuff.h>
> >>>>>
> >>>>> static DEFINE_IDA(mana_adev_ida);
> >>>>>
> >>>>> @@ -289,6 +290,19 @@ netdev_tx_t mana_start_xmit(struct sk_buff
> >>>>> *skb, struct net_device *ndev)
> >>>>> cq = &apc->tx_qp[txq_idx].tx_cq;
> >>>>> tx_stats = &txq->stats;
> >>>>>
> >>>>> + BUILD_BUG_ON(MAX_TX_WQE_SGL_ENTRIES !=
> >>>>> MANA_MAX_TX_WQE_SGL_ENTRIES);
> >>>>> + #if (MAX_SKB_FRAGS + 2 > MANA_MAX_TX_WQE_SGL_ENTRIES)
> >>>>> + if (skb_shinfo(skb)->nr_frags + 2 >
> >>>>> MANA_MAX_TX_WQE_SGL_ENTRIES) {
> >>>>> + netdev_info_once(ndev,
> >>>>> + "nr_frags %d exceeds max
> >>>>> supported sge limit. Attempting skb_linearize\n",
> >>>>> + skb_shinfo(skb)->nr_frags);
> >>>>> + if (skb_linearize(skb)) {
> >>>>
> >>>> This will fail in many cases.
> >>>>
> >>>> This sort of check is better done in ndo_features_check()
> >>>>
> >>>> Most probably this would occur for GSO packets, so can ask a software
> >>>> segmentation
> >>>> to avoid this big and risky kmalloc() by all means.
> >>>>
> >>>> Look at idpf_features_check() which has something similar.
> >>>
> >>> Hi Eric,
> >>> Thank you for your review. I understand your concerns regarding the use
> >>> of skb_linearize() in the xmit path, as it can fail under memory
> >>> pressure and introduces additional overhead in the transmit path. Based
> >>> on your input, I will work on a v2 that will move the SGE limit check to
> >>> the ndo_features_check() path and for GSO skbs exceding the hw limit
> >>> will disable the NETIF_F_GSO_MASK to enforce software segmentation in
> >>> kernel before the call to xmit.
> >>> Also for non GSO skb exceeding the SGE hw limit should we go for using
> >>> skb_linearize only then or would you suggest some other approach here?
> >>
> >> I think that for non GSO, the linearization attempt is fine.
> >>
> >> Note that this is extremely unlikely for non malicious users,
> >> and MTU being usually small (9K or less),
> >> the allocation will be much smaller than a GSO packet.
> >
> > Okay. Will send a v2
> Hi Eric,
> I tested the code by disabling GSO in ndo_features_check when the number
> of SGEs exceeds the hardware limit, using iperf for a single TCP
> connection with zerocopy enabled. I noticed a significant difference in
> throughput compared to when we linearize the skbs.
> For reference, the throughput is 35.6 Gbits/sec when using
> skb_linearize, but drops to 6.75 Gbits/sec when disabling GSO per skb.
You must be doing something very wrong.
Difference between TSO and non TSO should not be that high.
ethtool -K eth0 tso on
netperf -H tjbp27
MIGRATED TCP STREAM TEST from ::0 (::) port 0 AF_INET6 to
tjbp27.prod.google.com () port 0 AF_INET6
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
540000 262144 262144 10.00 92766.69
ethtool -K eth0 tso off
netperf -H tjbp27
MIGRATED TCP STREAM TEST from ::0 (::) port 0 AF_INET6 to
tjbp27.prod.google.com () port 0 AF_INET6
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
540000 262144 262144 10.00 52218.97
Now if I force linearization, you can definitely see the very high
cost of the copies !
ethtool -K eth1 sg off
tjbp26:/home/edumazet# ./netperf -H tjbp27
MIGRATED TCP STREAM TEST from ::0 (::) port 0 AF_INET6 to
tjbp27.prod.google.com () port 0 AF_INET6
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
540000 262144 262144 10.00 16951.32
>
> Hence, We propose to linearizing skbs until the first failure occurs.
Hmm... basically hiding a bug then ?
> After that, we switch to a fail-safe mode by disabling GSO for SKBs with
> sge > hw limit using the ndo_feature_check implementation, while
> continuing to apply skb_linearize() for non-GSO packets that exceed the
> hardware limit. This ensures we remain on the optimal performance path
> initially, and only transition to the fail-safe path after encountering
> a failure.
Please post your patch (adding the check in ndo_features_check()),
perhaps one of us is able to help.
^ permalink raw reply
* RE: [PATCH] mshv: Fix deposit memory in MSHV_ROOT_HVCALL
From: Michael Kelley @ 2025-10-17 18:09 UTC (permalink / raw)
To: Nuno Das Neves, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, arnd@arndb.de, mrathor@linux.microsoft.com,
skinsburskii@linux.microsoft.com
In-Reply-To: <1d5a7098-dcbd-4a0c-aa6c-481f131b1491@linux.microsoft.com>
From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Friday, October 17, 2025 10:55 AM
>
> On 10/17/2025 10:33 AM, Michael Kelley wrote:
> > From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Friday, October 17, 2025 10:26 AM
> >>
> >> On 10/16/2025 6:12 PM, Michael Kelley wrote:
> >>> From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Thursday, October 16, 2025 12:54 PM
> >>>>
> >>>> When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
> >>>> HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
> >>>> -EAGAIN to userspace.
> >>>>
> >>>> However, it's much easier and efficient if the driver simply deposits
> >>>> memory on demand and immediately retries the hypercall as is done with
> >>>> all the other hypercall helper functions.
> >>>>
> >>>> But unlike those, in MSHV_ROOT_HVCALL the input is opaque to the
> >>>> kernel. This is problematic for rep hypercalls, because the next part
> >>>> of the input list can't be copied on each loop after depositing pages
> >>>> (this was the original reason for returning -EAGAIN in this case).
> >>>>
> >>>> Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
> >>>> parameter. This solves the issue, allowing the deposit loop in
> >>>> MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
> >>>> partway through.
> >>>
> >>> >From reading the above, I'm pretty sure this code change is an
> >>> optimization that lets user space avoid having to deal with the
> >>> -EAGAIN result by resubmitting the ioctl with a different
> >>> starting point for a rep hypercall. As such, I'd suggest the patch
> >>> title should be "Improve deposit memory ...." (or something similar).
> >>> The word "Fix" makes it sound like a bug fix.
> >>>
> >>> Or is user space code currently faulty in its handling of -EAGAIN, and
> >>> this really is an indirect bug fix to make things work? If so, do you
> >>> want a Fixes: tag so the change is backported?
> >>>
> >>
> >> It's the latter case, userspace doesn't handle it correctly, so I
> >> consider it a fix more than just an improvement.
> >
> > OK, thanks. You might want to tweak the commit message a bit
> > to clarify that this really is a bug fix and why. I was leaning
> > toward the wrong conclusion based on the current commit
> > message.
> >
>
> Is this clearer?
>
> "
> mshv: Fix deposit memory in MSHV_ROOT_HVCALL
>
> When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
> HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
> -EAGAIN to userspace. The expectation is that the VMM will retry.
>
> However, some VMM code in the wild doesn't do this and simply fails.
> Rather than force the VMM to retry, change the ioctl to deposit
> memory on demand and immediately retry the hypercall as is done with
> all the other hypercall helper functions.
>
> In addition to making the ioctl easier to use, removing the need for
> multiple syscalls improves performance.
>
> There is a complication: unlike the other hypercall helper functions,
> in MSHV_ROOT_HVCALL the input is opaque to the kernel. This is
> problematic for rep hypercalls, because the next part of the input
> list can't be copied on each loop after depositing pages (this was
> the original reason for returning -EAGAIN in this case).
>
> Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
> parameter. This solves the issue, allowing the deposit loop in
> MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
> partway through.
Yes, that works for me. Thanks.
Michael
^ permalink raw reply
* RE: [PATCH v9 0/2] Drivers: hv: Introduce new driver - mshv_vtl
From: Michael Kelley @ 2025-10-17 18:32 UTC (permalink / raw)
To: Naman Jain, K . Y . Srinivasan, Haiyang Zhang, Wei Liu,
Dexuan Cui, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, H . Peter Anvin
Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, Mukesh Rathor, Stanislav Kinsburskii,
Nuno Das Neves, Peter Zijlstra, Sean Christopherson,
Paolo Bonzini, Christoph Hellwig, Saurabh Sengar, ALOK TIWARI
In-Reply-To: <20251017074507.142704-1-namjain@linux.microsoft.com>
From: Naman Jain <namjain@linux.microsoft.com> Sent: Friday, October 17, 2025 12:45 AM
>
> Introduce a new mshv_vtl driver to provide an interface for Virtual
> Machine Monitor like OpenVMM and its use as OpenHCL paravisor to
> control VTL0 (Virtual trust Level).
> Expose devices and support IOCTLs for features like VTL creation,
> VTL0 memory management, context switch, making hypercalls,
> mapping VTL0 address space to VTL2 userspace, getting new VMBus
> messages and channel events in VTL2 etc.
>
> OpenVMM : https://openvmm.dev/guide/
>
> Changes since v8:
> https://lore.kernel.org/all/20251013060353.67326-1-namjain@linux.microsoft.com/
> Addressed Sean's comments:
> * Removed forcing SIGPENDING, and other minor changes, in
> mshv_vtl_ioctl_return_to_lower_vtl after referring
> to Sean's earlier changes for xfer_to_guest_mode_handle_work.
>
> * Rebased and resolved merge conflicts, compilation errors on latest
> linux-next kernel tip, after Roman's Confidential VM changes,
> which merged recently. No functional changes.
Did your testing against the latest linux-next included testing with
CONFIG_X86_KERNEL_IBT=y? This is Indirect Branch Tracking, which would
have generated a fault with your v7 series and earlier because of the indirect
call instruction when doing VTL Return through the hypercall page (which
doesn't have the needed ENDBR64 instruction). But now that VTL Return is
doing a static call, that should be direct, which won't trigger an IBT fault.
To confirm that you really are running with IBT enabled, you should see
[ 0.047008] CET detected: Indirect Branch Tracking enabled
in the VTL2 dmesg output. And "ibt" should appear in the
"flags" output line of 'cat /proc/cpuinfo' (or the 'lscpu' command).
Michael
^ permalink raw reply
* [PATCH v2] mshv: Fix deposit memory in MSHV_ROOT_HVCALL
From: Nuno Das Neves @ 2025-10-17 18:58 UTC (permalink / raw)
To: linux-hyperv, linux-kernel, mhklinux
Cc: kys, haiyangz, wei.liu, decui, arnd, mrathor, skinsburskii,
Nuno Das Neves
When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
-EAGAIN to userspace. The expectation is that the VMM will retry.
However, some VMM code in the wild doesn't do this and simply fails.
Rather than force the VMM to retry, change the ioctl to deposit
memory on demand and immediately retry the hypercall as is done with
all the other hypercall helper functions.
In addition to making the ioctl easier to use, removing the need for
multiple syscalls improves performance.
There is a complication: unlike the other hypercall helper functions,
in MSHV_ROOT_HVCALL the input is opaque to the kernel. This is
problematic for rep hypercalls, because the next part of the input
list can't be copied on each loop after depositing pages (this was
the original reason for returning -EAGAIN in this case).
Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
parameter. This solves the issue, allowing the deposit loop in
MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
partway through.
Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
---
Changes in v2:
- Improve commit message [Michael]
- Fix up some incorrect/incomplete comments [Michael]
---
drivers/hv/mshv_root_main.c | 58 ++++++++++++++++++----------------
include/asm-generic/mshyperv.h | 17 ++++++++--
2 files changed, 44 insertions(+), 31 deletions(-)
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 9ae67c6e9f60..64e1bdf3b57c 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -159,6 +159,7 @@ static int mshv_ioctl_passthru_hvcall(struct mshv_partition *partition,
unsigned int pages_order;
void *input_pg = NULL;
void *output_pg = NULL;
+ u16 reps_completed;
if (copy_from_user(&args, user_args, sizeof(args)))
return -EFAULT;
@@ -210,41 +211,42 @@ static int mshv_ioctl_passthru_hvcall(struct mshv_partition *partition,
*/
*(u64 *)input_pg = partition->pt_id;
- if (args.reps)
- status = hv_do_rep_hypercall(args.code, args.reps, 0,
- input_pg, output_pg);
- else
- status = hv_do_hypercall(args.code, input_pg, output_pg);
-
- if (hv_result(status) == HV_STATUS_CALL_PENDING) {
- if (is_async) {
- mshv_async_hvcall_handler(partition, &status);
- } else { /* Paranoia check. This shouldn't happen! */
- ret = -EBADFD;
- goto free_pages_out;
+ reps_completed = 0;
+ do {
+ if (args.reps) {
+ status = hv_do_rep_hypercall_ex(args.code, args.reps,
+ 0, reps_completed,
+ input_pg, output_pg);
+ reps_completed = hv_repcomp(status);
+ } else {
+ status = hv_do_hypercall(args.code, input_pg, output_pg);
}
- }
- if (hv_result(status) == HV_STATUS_INSUFFICIENT_MEMORY) {
- ret = hv_call_deposit_pages(NUMA_NO_NODE, partition->pt_id, 1);
- if (!ret)
- ret = -EAGAIN;
- } else if (!hv_result_success(status)) {
- ret = hv_result_to_errno(status);
- }
+ if (hv_result(status) == HV_STATUS_CALL_PENDING) {
+ if (is_async) {
+ mshv_async_hvcall_handler(partition, &status);
+ } else { /* Paranoia check. This shouldn't happen! */
+ ret = -EBADFD;
+ goto free_pages_out;
+ }
+ }
+
+ if (hv_result_success(status))
+ break;
+
+ if (hv_result(status) != HV_STATUS_INSUFFICIENT_MEMORY)
+ ret = hv_result_to_errno(status);
+ else
+ ret = hv_call_deposit_pages(NUMA_NO_NODE,
+ partition->pt_id, 1);
+ } while (!ret);
- /*
- * Always return the status and output data regardless of result.
- * The VMM may need it to determine how to proceed. E.g. the status may
- * contain the number of reps completed if a rep hypercall partially
- * succeeded.
- */
args.status = hv_result(status);
- args.reps = args.reps ? hv_repcomp(status) : 0;
+ args.reps = reps_completed;
if (copy_to_user(user_args, &args, sizeof(args)))
ret = -EFAULT;
- if (output_pg &&
+ if (!ret && output_pg &&
copy_to_user((void __user *)args.out_ptr, output_pg, args.out_sz))
ret = -EFAULT;
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index ebf458dbcf84..ecedab554c80 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -126,10 +126,12 @@ static inline unsigned int hv_repcomp(u64 status)
/*
* Rep hypercalls. Callers of this functions are supposed to ensure that
- * rep_count and varhead_size comply with Hyper-V hypercall definition.
+ * rep_count, varhead_size, and rep_start comply with Hyper-V hypercall
+ * definition.
*/
-static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
- void *input, void *output)
+static inline u64 hv_do_rep_hypercall_ex(u16 code, u16 rep_count,
+ u16 varhead_size, u16 rep_start,
+ void *input, void *output)
{
u64 control = code;
u64 status;
@@ -137,6 +139,7 @@ static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
control |= (u64)varhead_size << HV_HYPERCALL_VARHEAD_OFFSET;
control |= (u64)rep_count << HV_HYPERCALL_REP_COMP_OFFSET;
+ control |= (u64)rep_start << HV_HYPERCALL_REP_START_OFFSET;
do {
status = hv_do_hypercall(control, input, output);
@@ -154,6 +157,14 @@ static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
return status;
}
+/* For the typical case where rep_start is 0 */
+static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
+ void *input, void *output)
+{
+ return hv_do_rep_hypercall_ex(code, rep_count, varhead_size, 0,
+ input, output);
+}
+
/* Generate the guest OS identifier as described in the Hyper-V TLFS */
static inline u64 hv_generate_guest_id(u64 kernel_version)
{
--
2.34.1
^ permalink raw reply related
* RE: [PATCH v2] mshv: Fix deposit memory in MSHV_ROOT_HVCALL
From: Michael Kelley @ 2025-10-17 19:25 UTC (permalink / raw)
To: Nuno Das Neves, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, arnd@arndb.de, mrathor@linux.microsoft.com,
skinsburskii@linux.microsoft.com
In-Reply-To: <1760727497-21158-1-git-send-email-nunodasneves@linux.microsoft.com>
From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Friday, October 17, 2025 11:58 AM
>
> When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
> HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
> -EAGAIN to userspace. The expectation is that the VMM will retry.
>
> However, some VMM code in the wild doesn't do this and simply fails.
> Rather than force the VMM to retry, change the ioctl to deposit
> memory on demand and immediately retry the hypercall as is done with
> all the other hypercall helper functions.
>
> In addition to making the ioctl easier to use, removing the need for
> multiple syscalls improves performance.
>
> There is a complication: unlike the other hypercall helper functions,
> in MSHV_ROOT_HVCALL the input is opaque to the kernel. This is
> problematic for rep hypercalls, because the next part of the input
> list can't be copied on each loop after depositing pages (this was
> the original reason for returning -EAGAIN in this case).
>
> Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
> parameter. This solves the issue, allowing the deposit loop in
> MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
> partway through.
>
> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
>
> Changes in v2:
> - Improve commit message [Michael]
> - Fix up some incorrect/incomplete comments [Michael]
>
> ---
> drivers/hv/mshv_root_main.c | 58 ++++++++++++++++++----------------
> include/asm-generic/mshyperv.h | 17 ++++++++--
> 2 files changed, 44 insertions(+), 31 deletions(-)
>
^ permalink raw reply
* [PATCH] Hyper-V: add myself as maintainer
From: longli @ 2025-10-17 21:58 UTC (permalink / raw)
To: K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
linux-hyperv, linux-kernel
Cc: Long Li
From: Long Li <longli@microsoft.com>
Also include MANA RDMA driver in the Hyper-V maintained list.
Signed-off-by: Long Li <longli@microsoft.com>
---
MAINTAINERS | 3 +++
1 file changed, 3 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index a8a770714101..6912af480f9d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11399,6 +11399,7 @@ M: "K. Y. Srinivasan" <kys@microsoft.com>
M: Haiyang Zhang <haiyangz@microsoft.com>
M: Wei Liu <wei.liu@kernel.org>
M: Dexuan Cui <decui@microsoft.com>
+M: Long Li <longli@microsoft.com>
L: linux-hyperv@vger.kernel.org
S: Supported
T: git git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git
@@ -11416,6 +11417,7 @@ F: arch/x86/kernel/cpu/mshyperv.c
F: drivers/clocksource/hyperv_timer.c
F: drivers/hid/hid-hyperv.c
F: drivers/hv/
+F: drivers/infiniband/hw/mana/
F: drivers/input/serio/hyperv-keyboard.c
F: drivers/iommu/hyperv-iommu.c
F: drivers/net/ethernet/microsoft/
@@ -11435,6 +11437,7 @@ F: include/hyperv/hvhdk_mini.h
F: include/linux/hyperv.h
F: include/net/mana
F: include/uapi/linux/hyperv.h
+F: include/uapi/rdma/mana-abi.h
F: net/vmw_vsock/hyperv_transport.c
F: tools/hv/
--
2.34.1
^ permalink raw reply related
* Re: [PATCH v2] mshv: Fix deposit memory in MSHV_ROOT_HVCALL
From: Wei Liu @ 2025-10-17 22:06 UTC (permalink / raw)
To: Nuno Das Neves
Cc: linux-hyperv, linux-kernel, mhklinux, kys, haiyangz, wei.liu,
decui, arnd, mrathor, skinsburskii
In-Reply-To: <1760727497-21158-1-git-send-email-nunodasneves@linux.microsoft.com>
On Fri, Oct 17, 2025 at 11:58:17AM -0700, Nuno Das Neves wrote:
> When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets
> HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns
> -EAGAIN to userspace. The expectation is that the VMM will retry.
>
> However, some VMM code in the wild doesn't do this and simply fails.
> Rather than force the VMM to retry, change the ioctl to deposit
> memory on demand and immediately retry the hypercall as is done with
> all the other hypercall helper functions.
>
> In addition to making the ioctl easier to use, removing the need for
> multiple syscalls improves performance.
>
> There is a complication: unlike the other hypercall helper functions,
> in MSHV_ROOT_HVCALL the input is opaque to the kernel. This is
> problematic for rep hypercalls, because the next part of the input
> list can't be copied on each loop after depositing pages (this was
> the original reason for returning -EAGAIN in this case).
>
> Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start'
> parameter. This solves the issue, allowing the deposit loop in
> MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages
> partway through.
>
> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
In v1 you said you will add a "Fixes" tag. Where is it?
Wei
^ permalink raw reply
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