* [PATCH v7 1/9] x86/acpi: Add functions to setup and access the wakeup mailbox
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-24 16:01 ` Rafael J. Wysocki
2025-11-17 17:02 ` [PATCH v7 2/9] dt-bindings: reserved-memory: Wakeup Mailbox for Intel processors Ricardo Neri
` (8 subsequent siblings)
9 siblings, 1 reply; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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
Systems that describe hardware using DeviceTree graphs may enumerate and
implement the wakeup mailbox as defined in the ACPI specification but do
not otherwise depend on ACPI. Expose functions to setup and access the
location of the wakeup mailbox from outside ACPI code.
The function acpi_setup_mp_wakeup_mailbox() stores the physical address of
the mailbox and updates the wakeup_secondary_cpu_64() APIC callback.
The function acpi_madt_multiproc_wakeup_mailbox() returns a pointer to the
mailbox.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes in v7:
- Moved function declarations to arch/x86/include/asm/acpi.h
- Added stubs for !CONFIG_ACPI.
- Do not use these new functions in madt_wakeup.c.
- Dropped Acked-by and Reviewed-by tags from Rafael and Dexuan as this
patch changed.
Changes in v6:
- 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 in v5:
- None
Changes in v4:
- 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 in v3:
- Introduced this patch.
Changes in v2:
- N/A
---
arch/x86/include/asm/acpi.h | 10 ++++++++++
arch/x86/kernel/acpi/madt_wakeup.c | 11 +++++++++++
2 files changed, 21 insertions(+)
diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
index a03aa6f999d1..820df375df79 100644
--- a/arch/x86/include/asm/acpi.h
+++ b/arch/x86/include/asm/acpi.h
@@ -182,6 +182,9 @@ void __iomem *x86_acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
#define acpi_os_ioremap acpi_os_ioremap
#endif
+void acpi_setup_mp_wakeup_mailbox(u64 addr);
+struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void);
+
#else /* !CONFIG_ACPI */
#define acpi_lapic 0
@@ -200,6 +203,13 @@ static inline u64 x86_default_get_root_pointer(void)
return 0;
}
+static inline void acpi_setup_mp_wakeup_mailbox(u64 addr) { }
+
+static inline struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
+{
+ return NULL;
+}
+
#endif /* !CONFIG_ACPI */
#define ARCH_HAS_POWER_INIT 1
diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
index 6d7603511f52..82caf44b45e3 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -247,3 +247,14 @@ 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;
+}
--
2.43.0
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH v7 1/9] x86/acpi: Add functions to setup and access the wakeup mailbox
2025-11-17 17:02 ` [PATCH v7 1/9] x86/acpi: Add functions to setup and access the wakeup mailbox Ricardo Neri
@ 2025-11-24 16:01 ` Rafael J. Wysocki
2025-11-26 2:20 ` Ricardo Neri
0 siblings, 1 reply; 14+ messages in thread
From: Rafael J. Wysocki @ 2025-11-24 16:01 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
On Mon, Nov 17, 2025 at 6:04 PM Ricardo Neri
<ricardo.neri-calderon@linux.intel.com> wrote:
>
> Systems that describe hardware using DeviceTree graphs may enumerate and
> implement the wakeup mailbox as defined in the ACPI specification but do
> not otherwise depend on ACPI. Expose functions to setup and access the
> location of the wakeup mailbox from outside ACPI code.
>
> The function acpi_setup_mp_wakeup_mailbox() stores the physical address of
> the mailbox and updates the wakeup_secondary_cpu_64() APIC callback.
>
> The function acpi_madt_multiproc_wakeup_mailbox() returns a pointer to the
> mailbox.
>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
> ---
> Changes in v7:
> - Moved function declarations to arch/x86/include/asm/acpi.h
> - Added stubs for !CONFIG_ACPI.
> - Do not use these new functions in madt_wakeup.c.
> - Dropped Acked-by and Reviewed-by tags from Rafael and Dexuan as this
> patch changed.
>
> Changes in v6:
> - 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 in v5:
> - None
>
> Changes in v4:
> - 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 in v3:
> - Introduced this patch.
>
> Changes in v2:
> - N/A
> ---
> arch/x86/include/asm/acpi.h | 10 ++++++++++
> arch/x86/kernel/acpi/madt_wakeup.c | 11 +++++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
> index a03aa6f999d1..820df375df79 100644
> --- a/arch/x86/include/asm/acpi.h
> +++ b/arch/x86/include/asm/acpi.h
> @@ -182,6 +182,9 @@ void __iomem *x86_acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
> #define acpi_os_ioremap acpi_os_ioremap
> #endif
>
> +void acpi_setup_mp_wakeup_mailbox(u64 addr);
> +struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void);
> +
> #else /* !CONFIG_ACPI */
>
> #define acpi_lapic 0
> @@ -200,6 +203,13 @@ static inline u64 x86_default_get_root_pointer(void)
> return 0;
> }
>
> +static inline void acpi_setup_mp_wakeup_mailbox(u64 addr) { }
> +
> +static inline struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
> +{
> + return NULL;
> +}
> +
> #endif /* !CONFIG_ACPI */
>
> #define ARCH_HAS_POWER_INIT 1
> diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
> index 6d7603511f52..82caf44b45e3 100644
> --- a/arch/x86/kernel/acpi/madt_wakeup.c
> +++ b/arch/x86/kernel/acpi/madt_wakeup.c
> @@ -247,3 +247,14 @@ 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;
> +}
>
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH v7 1/9] x86/acpi: Add functions to setup and access the wakeup mailbox
2025-11-24 16:01 ` Rafael J. Wysocki
@ 2025-11-26 2:20 ` Ricardo Neri
0 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-26 2:20 UTC (permalink / raw)
To: Rafael J. Wysocki
Cc: x86, Krzysztof Kozlowski, Conor Dooley, Rob Herring,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Michael Kelley, Saurabh Sengar, Chris Oo, Kirill A. Shutemov,
linux-hyperv, devicetree, linux-acpi, linux-kernel, Ricardo Neri
On Mon, Nov 24, 2025 at 05:01:11PM +0100, Rafael J. Wysocki wrote:
> On Mon, Nov 17, 2025 at 6:04 PM Ricardo Neri
> <ricardo.neri-calderon@linux.intel.com> wrote:
> >
> > Systems that describe hardware using DeviceTree graphs may enumerate and
> > implement the wakeup mailbox as defined in the ACPI specification but do
> > not otherwise depend on ACPI. Expose functions to setup and access the
> > location of the wakeup mailbox from outside ACPI code.
> >
> > The function acpi_setup_mp_wakeup_mailbox() stores the physical address of
> > the mailbox and updates the wakeup_secondary_cpu_64() APIC callback.
> >
> > The function acpi_madt_multiproc_wakeup_mailbox() returns a pointer to the
> > mailbox.
> >
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
>
> Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Thanks Rafael!
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v7 2/9] dt-bindings: reserved-memory: Wakeup Mailbox for Intel processors
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 1/9] x86/acpi: Add functions to setup and access the wakeup mailbox Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 3/9] x86/dt: Parse the " Ricardo Neri
` (7 subsequent siblings)
9 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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 (Intel), Yunhong Jiang, Ricardo Neri
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 (Intel) <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 in v7:
- Fixed Acked-by tag from Rafael to include the "(Intel)" suffix.
Changes in v6:
- 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 in v5:
- 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 in v4:
- 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 in v3:
- 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 in v2:
- 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 [flat|nested] 14+ messages in thread* [PATCH v7 3/9] x86/dt: Parse the Wakeup Mailbox for Intel processors
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 1/9] x86/acpi: Add functions to setup and access the wakeup mailbox Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 2/9] dt-bindings: reserved-memory: Wakeup Mailbox for Intel processors Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 4/9] x86/hyperv/vtl: Set real_mode_header in hv_vtl_init_platform() Ricardo Neri
` (6 subsequent siblings)
9 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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
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 in v7:
- #included asm/acpi.h to reflect the updated declaration of the
needed functions.
- (Kept Reviewed-by tag from Dexuan, as this single change is trivial.)
Changes in v6:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes in v5:
- Made CONFIG_X86_MAILBOX_WAKEUP depend on CONFIG_OF or CONFIG_ACPI_
MADT_WAKEUP.
Changes in v4:
- 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 in v3:
- 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 in v2:
- Disabled CPU offlining.
- Modified dtb_parse_mp_wake() to return the address of the mailbox.
---
arch/x86/kernel/devicetree.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)
diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
index dd8748c45529..318acaecb5ca 100644
--- a/arch/x86/kernel/devicetree.c
+++ b/arch/x86/kernel/devicetree.c
@@ -18,6 +18,7 @@
#include <linux/of_pci.h>
#include <linux/initrd.h>
+#include <asm/acpi.h>
#include <asm/irqdomain.h>
#include <asm/hpet.h>
#include <asm/apic.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 [flat|nested] 14+ messages in thread* [PATCH v7 4/9] x86/hyperv/vtl: Set real_mode_header in hv_vtl_init_platform()
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
` (2 preceding siblings ...)
2025-11-17 17:02 ` [PATCH v7 3/9] x86/dt: Parse the " Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 5/9] x86/realmode: Make the location of the trampoline configurable Ricardo Neri
` (5 subsequent siblings)
9 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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
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 in v7:
- None
Changes in v6:
- Corrected reference to hv_vtl_init_platform() in the changelog.
(Dexuan)
- Added Reviewed-by tag from Dexuan. Thanks!
Changes in v5:
- None
Changes in v4:
- Added Reviewed-by tag from Michael. Thanks!
Changes in v3:
- Edited the commit message for clarity.
Changes in v2:
- 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 [flat|nested] 14+ messages in thread* [PATCH v7 5/9] x86/realmode: Make the location of the trampoline configurable
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
` (3 preceding siblings ...)
2025-11-17 17:02 ` [PATCH v7 4/9] x86/hyperv/vtl: Set real_mode_header in hv_vtl_init_platform() Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 6/9] x86/hyperv/vtl: Setup the 64-bit trampoline for TDX guests Ricardo Neri
` (4 subsequent siblings)
9 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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
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 in v7:
- None
Changes in v6:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes in v5:
- None
Changes in v4:
- Added Reviewed-by tag from Michael. Thanks!
Changes in v3:
- 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 in v2:
- 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 [flat|nested] 14+ messages in thread* [PATCH v7 6/9] x86/hyperv/vtl: Setup the 64-bit trampoline for TDX guests
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
` (4 preceding siblings ...)
2025-11-17 17:02 ` [PATCH v7 5/9] x86/realmode: Make the location of the trampoline configurable Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 7/9] x86/acpi: Add a helper get the address of the wakeup mailbox Ricardo Neri
` (3 subsequent siblings)
9 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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
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 in v7:
- None
Changes in v6:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes in v5:
- None
Changes in v4:
- Added Reviewed-by tag from Michael. Thanks!
Changes in v3:
- Added a note regarding there is no need to check for a present
paravisor.
- Edited commit message for clarity.
Changes in v2:
- 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 [flat|nested] 14+ messages in thread* [PATCH v7 7/9] x86/acpi: Add a helper get the address of the wakeup mailbox
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
` (5 preceding siblings ...)
2025-11-17 17:02 ` [PATCH v7 6/9] x86/hyperv/vtl: Setup the 64-bit trampoline for TDX guests Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-24 16:03 ` Rafael J. Wysocki
2025-11-17 17:02 ` [PATCH v7 8/9] x86/hyperv/vtl: Mark the wakeup mailbox page as private Ricardo Neri
` (2 subsequent siblings)
9 siblings, 1 reply; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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
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.
Suggested-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes in v7:
- Moved the added function to arch/x86/kernel/acpi/madt_wakeup.c
- Dropped Reviewed-by tags from Dexuan and Michael as this patch
changed.
Changes in v6:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes in v5:
- None
Changes in v4:
- Renamed function to acpi_get_mp_wakeup_mailbox_paddr().
- Added Reviewed-by tag from Michael. Thanks!
Changes in v3:
- Introduced this patch
Changes in v2:
- N/A
---
arch/x86/include/asm/acpi.h | 6 ++++++
arch/x86/kernel/acpi/madt_wakeup.c | 5 +++++
2 files changed, 11 insertions(+)
diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
index 820df375df79..c4e6459bd56b 100644
--- a/arch/x86/include/asm/acpi.h
+++ b/arch/x86/include/asm/acpi.h
@@ -184,6 +184,7 @@ void __iomem *x86_acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
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_ACPI */
@@ -210,6 +211,11 @@ static inline struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mail
return NULL;
}
+static inline u64 acpi_get_mp_wakeup_mailbox_paddr(void)
+{
+ return 0;
+}
+
#endif /* !CONFIG_ACPI */
#define ARCH_HAS_POWER_INIT 1
diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
index 82caf44b45e3..48734e4a6e8f 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -258,3 +258,8 @@ 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 [flat|nested] 14+ messages in thread* Re: [PATCH v7 7/9] x86/acpi: Add a helper get the address of the wakeup mailbox
2025-11-17 17:02 ` [PATCH v7 7/9] x86/acpi: Add a helper get the address of the wakeup mailbox Ricardo Neri
@ 2025-11-24 16:03 ` Rafael J. Wysocki
0 siblings, 0 replies; 14+ messages in thread
From: Rafael J. Wysocki @ 2025-11-24 16:03 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
On Mon, Nov 17, 2025 at 6:04 PM Ricardo Neri
<ricardo.neri-calderon@linux.intel.com> wrote:
>
> 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.
>
> Suggested-by: Michael Kelley <mhklinux@outlook.com>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
> ---
> Changes in v7:
> - Moved the added function to arch/x86/kernel/acpi/madt_wakeup.c
> - Dropped Reviewed-by tags from Dexuan and Michael as this patch
> changed.
>
> Changes in v6:
> - Added Reviewed-by tag from Dexuan. Thanks!
>
> Changes in v5:
> - None
>
> Changes in v4:
> - Renamed function to acpi_get_mp_wakeup_mailbox_paddr().
> - Added Reviewed-by tag from Michael. Thanks!
>
> Changes in v3:
> - Introduced this patch
>
> Changes in v2:
> - N/A
> ---
> arch/x86/include/asm/acpi.h | 6 ++++++
> arch/x86/kernel/acpi/madt_wakeup.c | 5 +++++
> 2 files changed, 11 insertions(+)
>
> diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
> index 820df375df79..c4e6459bd56b 100644
> --- a/arch/x86/include/asm/acpi.h
> +++ b/arch/x86/include/asm/acpi.h
> @@ -184,6 +184,7 @@ void __iomem *x86_acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
>
> 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_ACPI */
>
> @@ -210,6 +211,11 @@ static inline struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mail
> return NULL;
> }
>
> +static inline u64 acpi_get_mp_wakeup_mailbox_paddr(void)
> +{
> + return 0;
> +}
> +
> #endif /* !CONFIG_ACPI */
>
> #define ARCH_HAS_POWER_INIT 1
> diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
> index 82caf44b45e3..48734e4a6e8f 100644
> --- a/arch/x86/kernel/acpi/madt_wakeup.c
> +++ b/arch/x86/kernel/acpi/madt_wakeup.c
> @@ -258,3 +258,8 @@ 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 [flat|nested] 14+ messages in thread
* [PATCH v7 8/9] x86/hyperv/vtl: Mark the wakeup mailbox page as private
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
` (6 preceding siblings ...)
2025-11-17 17:02 ` [PATCH v7 7/9] x86/acpi: Add a helper get the address of the wakeup mailbox Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-17 17:02 ` [PATCH v7 9/9] x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs Ricardo Neri
2025-11-18 5:13 ` [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a " Ricardo Neri
9 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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
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.
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changed since v7:
- Dropped check for !CONFIG_X86_MAILBOX_WAKEUP. The symbol is no longer
valid and now we have a stub for !CONFIG_ACPI.
- Dropped Reviewed-by tags from Dexuan and Michael as this patch
changed.
Changes in v6:
- Fixed a compile error with !CONFIG_X86_MAILBOX_WAKEUP.
- Added Reviewed-by tag from Dexuan. Thanks!
Changes in v5:
- None
Changes in v4:
- Updated to use the renamed function acpi_get_mp_wakeup_mailbox_paddr().
- Added Reviewed-by tag from Michael. Thanks!
Changes in v3:
- Use the new helper function get_mp_wakeup_mailbox_paddr().
- Edited the commit message for clarity.
Changes in v2:
- 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 | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index ca0d23206e67..812d8a434966 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -6,6 +6,7 @@
* Saurabh Sengar <ssengar@microsoft.com>
*/
+#include <asm/acpi.h>
#include <asm/apic.h>
#include <asm/boot.h>
#include <asm/desc.h>
@@ -54,6 +55,18 @@ 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)
+{
+ u64 mb_addr = acpi_get_mp_wakeup_mailbox_paddr();
+
+ return mb_addr && within_page(addr, mb_addr);
+}
+
void __init hv_vtl_init_platform(void)
{
/*
@@ -66,6 +79,8 @@ 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 [flat|nested] 14+ messages in thread* [PATCH v7 9/9] x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
` (7 preceding siblings ...)
2025-11-17 17:02 ` [PATCH v7 8/9] x86/hyperv/vtl: Mark the wakeup mailbox page as private Ricardo Neri
@ 2025-11-17 17:02 ` Ricardo Neri
2025-11-18 5:13 ` [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a " Ricardo Neri
9 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-17 17:02 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
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 in v7:
- None
Changes in v6:
- Added Reviewed-by tag from Dexuan. Thanks!
Changes in v5:
- None
Changes in v4:
- Added Reviewed-by tag from Michael. Thanks!
Changes in v3:
- Unconditionally use the wakeup mailbox in a TDX confidential VM.
(Michael).
- Edited the commit message for clarity.
Changes in v2:
- 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 812d8a434966..431218ad6624 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -265,7 +265,15 @@ 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 [flat|nested] 14+ messages in thread* Re: [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs
2025-11-17 17:02 [PATCH v7 0/9] x86/hyperv/hv_vtl: Use a wakeup mailbox to boot secondary CPUs Ricardo Neri
` (8 preceding siblings ...)
2025-11-17 17:02 ` [PATCH v7 9/9] x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs Ricardo Neri
@ 2025-11-18 5:13 ` Ricardo Neri
9 siblings, 0 replies; 14+ messages in thread
From: Ricardo Neri @ 2025-11-18 5:13 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 (Intel), Yunhong Jiang, Thomas Gleixner
On Mon, Nov 17, 2025 at 09:02:46AM -0800, Ricardo Neri wrote:
> Hi,
>
> Many thanks to Boris, Rafael, Rob, and Dexuan for their valuable feedback!
> The main change in this version is the removal of the patch that moved the
> ACPI mailbox code from the x86 ACPI subsystem to a generic location. Users
> with DeviceTree-based firmware who wish use the ACPI wakeup mailbox need to
> select CONFIG_ACPI=y.
Also, this patchset uncovered, IMHO, missing definitions in arch/x86/asm/
topology.h. I posted a patch for that effect here:
https://lore.kernel.org/all/20251117-rneri-topology-cpuinfo-bug-v1-1-a905bb5f91e2@linux.intel.com/
I can repost this patchset along with the patch above if it makes things
easier.
BR,
Ricardo
^ permalink raw reply [flat|nested] 14+ messages in thread