[PATCH hyperv-next v6 00/17] Confidential VMBus

[PATCH hyperv-next v6 00/17] Confidential VMBus

[Roman Kisel]

Greetings everyone,

We've got to the 6th version of the patch series, and the full changelog
is at the end of the cover letter. I addressed feedback from
Michael and Wei on the previous version of the patch series.

Since v5, the fallback mechanism for establishing the VMBus connection
is no longer used as the availability of the Confidential VMBus is
now indicated by a bit in the Virtualization Stack (VS) CPUID leaf.
The v6 patch series breaks that out into a separate patch seizing
the opportunity to refactor the code that uses the same leaf.

That is obviously an x86_64 specific technique. On ARM64, the
Confidential VMBus is expected to be required once support for ARM CCA is
implemented. Despite that change, the functions for getting and setting
registers via paravisor remain fallible. That provides a clearer root cause
for failures instead of printing messages about unchecked MSR accesses.
That might seem as not needed with the paravisors run in Azure (OpenHCL
and the TrustedLauch aka HCL paravisor). However, if someone decides to
implement their own or tweak the exisiting one, this will help with debugging.

TLDR; is that these patches are for the Hyper-V guests, and the patches
allow to keep data flowing from physical devices into the guests encrypted
at the CPU level so that neither the root/host partition nor the hypervisor
can access the data being processed (they only "see" the encrypted/garbled
data) unless the guest decides to share it. The changes are backward compatible
with older systems, and their full potential is realized on hardware that
supports memory encryption.

These features also require running a paravisor, such as
OpenHCL (https://github.com/microsoft/openvmm) used in Azure. Another
implementation of the functionality available in this patch set is
available in the Hyper-V UEFI: https://github.com/microsoft/mu_msvm.

A more detailed description of the patches follows.

The guests running on Hyper-V can be confidential where the memory and the
register content are encrypted, provided that the hardware supports that
(currently support for AMD SEV-SNP and Intel TDX is implemented) and the guest
is capable of using these features. The confidential guests cannot be
introspected by the host nor the hypervisor without the guest sharing the
memory contents upon doing which the memory is decrypted.

In the confidential guests, neither the host nor the hypervisor need to be
trusted, and the guests processing sensitive data can take advantage of that.

Not trusting the host and the hypervisor (removing them from the Trusted
Computing Base aka TCB) necessitates that the method of communication
between the host and the guest be changed. Here is the data flow for a
conventional and the confidential VMBus connections (`C` stands for the
client or VSC, `S` for the server or VSP, the `DEVICE` is a physical one,
might be with multiple virtual functions):

1. Without the paravisor the devices are connected to the host, and the
host provides the device emulation or translation to the guest:

  +---- GUEST ----+       +----- DEVICE ----+        +----- HOST -----+
  |               |       |                 |        |                |
  |               |       |                 |        |                |
  |               |       |                 ==========                |
  |               |       |                 |        |                |
  |               |       |                 |        |                |
  |               |       |                 |        |                |
  +----- C -------+       +-----------------+        +------- S ------+
         ||                                                   ||
         ||                                                   ||
  +------||------------------ VMBus --------------------------||------+
  |                     Interrupts, MMIO                              |
  +-------------------------------------------------------------------+

2. With the paravisor, the devices are connected to the paravisor, and
the paravisor provides the device emulation or translation to the guest.
The guest doesn't communicate with the host directly, and the guest
communicates with the paravisor via the VMBus. The host is not trusted
in this model, and the paravisor is trusted:

  +---- GUEST --------------- VTL0 ------+               +-- DEVICE --+
  |                                      |               |            |
  | +- PARAVISOR --------- VTL2 -----+   |               |            |
  | |     +-- VMBus Relay ------+    ====+================            |
  | |     |   Interrupts, MMIO  |    |   |               |            |
  | |     +-------- S ----------+    |   |               +------------+
  | |               ||               |   |
  | +---------+     ||               |   |
  | |  Linux  |     ||    OpenHCL    |   |
  | |  kernel |     ||               |   |
  | +---- C --+-----||---------------+   |
  |       ||        ||                   |
  +-------++------- C -------------------+               +------------+
          ||                                             |    HOST    |
          ||                                             +---- S -----+
  +-------||----------------- VMBus ---------------------------||-----+
  |                     Interrupts, MMIO                              |
  +-------------------------------------------------------------------+

Note that in the second case the guest doesn't need to share the memory
with the host as it communicates only with the paravisor within their
partition boundary. That is precisely the raison d'etre and the value
proposition of this patch series: equip the confidential guest to use
private (encrypted) memory and rely on the paravisor when this is
available to be more secure.

An implementation of the VMBus relay that offers the Confidential VMBus
channels is available in the OpenVMM project as a part of the OpenHCL
paravisor. Please refer to

  * https://openvmm.dev/, and
  * https://github.com/microsoft/openvmm

for more information about the OpenHCL paravisor. A VMBus client
that can work with the Confidential VMBus is available in the
open-source Hyper-V UEFI: https://github.com/microsoft/mu_msvm.

I'd like to thank the following people for their help with this
patch series:

* Dexuan for help with validation and the fruitful discussions,
* Easwar for reviewing the refactoring of the page allocating and
  freeing in `hv.c`,
* John and Sven for the design,
* Mike for helping to avoid pitfalls when dealing with the GFP flags,
* Sven for blazing the trail and implementing the design in few
  codebases.

I made sure to validate the patch series on

    {TrustedLaunch(x86_64), OpenHCL} x
    {SNP(x86_64), TDX(x86_64), No hardware isolation, No paravisor} x
    {VMBus 5.0, VMBus 6.0} x
    {arm64, x86_64}.

[V6]
    - Rebased onto the latest hyperv-next tree.

    - Gave another thought to the fallible routines for getting and setting
      SynIC registers via paravisor introduced in the patch series, and after
      Michael's feedback decided to make them infallible as now we have the
      CPUID bit to indicate the availability of the Confidential VMBus. That
      simplifies the code and makes it clearer and more robust - a reflection
      of the improvements in the design throught the patch series iterations.
    - Removed the sentence discussing the fallback mechanism in the Documentation
      as it is no longer relevant.
      **Thank you, Michael!**

    - Avoided using the macro'es for (un)masking the proxy bit thanks to
      `union hv_synic_sint`.
      **Thank you, Wei!**

[V5] https://lore.kernel.org/linux-hyperv/20250828010557.123869-1-romank@linux.microsoft.com/
    - Rebased onto the latest hyperv-next tree.

    - Fixed build issues with the configs provided by the kernel robot.
      **Thank you, kernel robot!**

    - Fixed the potential NULL deref in a failure path.
      **Thank you, Michael!**

    - Removed the added blurb from the vmbus_drv.c with taxonomy of Hyper-V VMs
      that was providing reasons for the trade-offs in the fallback code. That
      code is no longer needed.

[V4] https://lore.kernel.org/linux-hyperv/20250714221545.5615-1-romank@linux.microsoft.com/
    - Rebased the patch series on top of the latest hyperv-next branch,
      applying changes as needed.

    - Fixed typos and clarifications all around the patch series.
    - Added clarifications in the patch 7 for `ms_hyperv.paravisor_present && !vmbus_is_confidential()`
      and using hypercalls vs SNP or TDX specific protocols.
      **Thank you, Alok!**

    - Trim the Documentation changes to 80 columns.
      **Thank you, Randy!**

    - Make sure adhere to the RST format, actually built the PDF docs
      and made sure the layout was correct.
    **Thank you, Jon!**

    - Better section order in Documentation.
    - Fixed the commit descriptions where suggested.
    - Moved EOI/EOM signaling for the confidential VMBus to the specialized function.
    - Removed the unused `cpu` parameters.
    - Clarified comments in the `hv_per_cpu_context` struct
    - Explicitly test for NULL and only call `iounmap()` if non-NULL instead of
      using `munmap()`.
    - Don't deallocate SynIC pages in the CPU online and offline paths.
    - Made sure the post page needs to be allocated for the future.
    - Added comments to describe trade-offs.
    **Thank you, Michael!**

[V3] https://lore.kernel.org/linux-hyperv/20250604004341.7194-1-romank@linux.microsoft.com/
    - The patch series is rebased on top of the latest hyperv-next branch.
    - Reworked the "wiring" diagram in the cover letter, added links to the
      OpenVMM project and the OpenHCL paravisor.

    - More precise wording in the comments and clearer code.
    **Thank you, Alok!**

    - Reworked the documentation patch.
    - Split the patchset into much more granular patches.
    - Various fixes and improvements throughout the patch series.
    **Thank you, Michael!**

[V2] https://lore.kernel.org/linux-hyperv/20250511230758.160674-1-romank@linux.microsoft.com/
    - The patch series is rebased on top of the latest hyperv-next branch.
  
    - Better wording in the commit messages and the Documentation.
    **Thank you, Alok and Wei!**

    - Removed the patches 5 and 6 concerning turning bounce buffering off from
      the previous version of the patch series as they were found to be
      architecturally unsound. The value proposition of the patch series is not
      diminished by this removal: these patches were an optimization and only for
      the storage (for the simplicity sake) but not for the network. These changes
      might be proposed in the future again after revolving the issues.
    ** Thanks you, Christoph, Dexuan, Dan, Michael, James, Robin! **

[V1] https://lore.kernel.org/linux-hyperv/20250409000835.285105-1-romank@linux.microsoft.com/

Roman Kisel (17):
  Documentation: hyperv: Confidential VMBus
  Drivers: hv: VMBus protocol version 6.0
  arch/x86: mshyperv: Discover Confidential VMBus availability
  arch: hyperv: Get/set SynIC synth.registers via paravisor
  arch/x86: mshyperv: Trap on access for some synthetic MSRs
  Drivers: hv: Rename fields for SynIC message and event pages
  Drivers: hv: Allocate the paravisor SynIC pages when required
  Drivers: hv: Post messages through the confidential VMBus if available
  Drivers: hv: remove stale comment
  Drivers: hv: Check message and event pages for non-NULL before
    iounmap()
  Drivers: hv: Rename the SynIC enable and disable routines
  Drivers: hv: Functions for setting up and tearing down the paravisor
    SynIC
  Drivers: hv: Allocate encrypted buffers when requested
  Drivers: hv: Free msginfo when the buffer fails to decrypt
  Drivers: hv: Support confidential VMBus channels
  Drivers: hv: Set the default VMBus version to 6.0
  Drivers: hv: Support establishing the confidential VMBus connection

 Documentation/virt/hyperv/coco.rst | 139 ++++++++++-
 arch/x86/kernel/cpu/mshyperv.c     |  77 ++++--
 drivers/hv/channel.c               |  73 ++++--
 drivers/hv/channel_mgmt.c          |  27 ++-
 drivers/hv/connection.c            |   6 +-
 drivers/hv/hv.c                    | 372 +++++++++++++++++++----------
 drivers/hv/hv_common.c             |  16 ++
 drivers/hv/hyperv_vmbus.h          |  75 +++++-
 drivers/hv/mshv_root.h             |   2 +-
 drivers/hv/mshv_synic.c            |   6 +-
 drivers/hv/ring_buffer.c           |   5 +-
 drivers/hv/vmbus_drv.c             | 186 ++++++++++-----
 include/asm-generic/mshyperv.h     |  45 +---
 include/hyperv/hvgdk_mini.h        |   1 +
 include/linux/hyperv.h             |  69 ++++--
 15 files changed, 793 insertions(+), 306 deletions(-)


base-commit: b595edcb24727e7f93e7962c3f6f971cc16dd29e
-- 
2.43.0

[PATCH hyperv-next v6 01/17] Documentation: hyperv: Confidential VMBus

[Roman Kisel]

Define what the confidential VMBus is and describe what advantages
it offers on the capable hardware.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 Documentation/virt/hyperv/coco.rst | 139 ++++++++++++++++++++++++++++-
 1 file changed, 138 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/hyperv/coco.rst b/Documentation/virt/hyperv/coco.rst
index c15d6fe34b4e..e00d94d9f88f 100644
--- a/Documentation/virt/hyperv/coco.rst
+++ b/Documentation/virt/hyperv/coco.rst
@@ -178,7 +178,7 @@ These Hyper-V and VMBus memory pages are marked as decrypted:
 
 * VMBus monitor pages
 
-* Synthetic interrupt controller (synic) related pages (unless supplied by
+* Synthetic interrupt controller (SynIC) related pages (unless supplied by
   the paravisor)
 
 * Per-cpu hypercall input and output pages (unless running with a paravisor)
@@ -232,6 +232,143 @@ with arguments explicitly describing the access. See
 _hv_pcifront_read_config() and _hv_pcifront_write_config() and the
 "use_calls" flag indicating to use hypercalls.
 
+Confidential VMBus
+------------------
+The confidential VMBus enables the confidential guest not to interact with
+the untrusted host partition and the untrusted hypervisor. Instead, the guest
+relies on the trusted paravisor to communicate with the devices processing
+sensitive data. The hardware (SNP or TDX) encrypts the guest memory and the
+register state while measuring the paravisor image using the platform security
+processor to ensure trusted and confidential computing.
+
+Confidential VMBus provides a secure communication channel between the guest
+and the paravisor, ensuring that sensitive data is protected from hypervisor-
+level access through memory encryption and register state isolation.
+
+Confidential VMBus is an extension of Confidential Computing (CoCo) VMs
+(a.k.a. "Isolated" VMs in Hyper-V terminology). Without Confidential VMBus,
+guest VMBus device drivers (the "VSC"s in VMBus terminology) communicate
+with VMBus servers (the VSPs) running on the Hyper-V host. The
+communication must be through memory that has been decrypted so the
+host can access it. With Confidential VMBus, one or more of the VSPs reside
+in the trusted paravisor layer in the guest VM. Since the paravisor layer also
+operates in encrypted memory, the memory used for communication with
+such VSPs does not need to be decrypted and thereby exposed to the
+Hyper-V host. The paravisor is responsible for communicating securely
+with the Hyper-V host as necessary.
+
+The data is transferred directly between the VM and a vPCI device (a.k.a.
+a PCI pass-thru device, see :doc:`vpci`) that is directly assigned to VTL2
+and that supports encrypted memory. In such a case, neither the host partition
+nor the hypervisor has any access to the data. The guest needs to establish
+a VMBus connection only with the paravisor for the channels that process
+sensitive data, and the paravisor abstracts the details of communicating
+with the specific devices away providing the guest with the well-established
+VSP (Virtual Service Provider) interface that has had support in the Hyper-V
+drivers for a decade.
+
+In the case the device does not support encrypted memory, the paravisor
+provides bounce-buffering, and although the data is not encrypted, the backing
+pages aren't mapped into the host partition through SLAT. While not impossible,
+it becomes much more difficult for the host partition to exfiltrate the data
+than it would be with a conventional VMBus connection where the host partition
+has direct access to the memory used for communication.
+
+Here is the data flow for a conventional VMBus connection (`C` stands for the
+client or VSC, `S` for the server or VSP, the `DEVICE` is a physical one, might
+be with multiple virtual functions)::
+
+  +---- GUEST ----+       +----- DEVICE ----+        +----- HOST -----+
+  |               |       |                 |        |                |
+  |               |       |                 |        |                |
+  |               |       |                 ==========                |
+  |               |       |                 |        |                |
+  |               |       |                 |        |                |
+  |               |       |                 |        |                |
+  +----- C -------+       +-----------------+        +------- S ------+
+         ||                                                   ||
+         ||                                                   ||
+  +------||------------------ VMBus --------------------------||------+
+  |                     Interrupts, MMIO                              |
+  +-------------------------------------------------------------------+
+
+and the Confidential VMBus connection::
+
+  +---- GUEST --------------- VTL0 ------+               +-- DEVICE --+
+  |                                      |               |            |
+  | +- PARAVISOR --------- VTL2 -----+   |               |            |
+  | |     +-- VMBus Relay ------+    ====+================            |
+  | |     |   Interrupts, MMIO  |    |   |               |            |
+  | |     +-------- S ----------+    |   |               +------------+
+  | |               ||               |   |
+  | +---------+     ||               |   |
+  | |  Linux  |     ||    OpenHCL    |   |
+  | |  kernel |     ||               |   |
+  | +---- C --+-----||---------------+   |
+  |       ||        ||                   |
+  +-------++------- C -------------------+               +------------+
+          ||                                             |    HOST    |
+          ||                                             +---- S -----+
+  +-------||----------------- VMBus ---------------------------||-----+
+  |                     Interrupts, MMIO                              |
+  +-------------------------------------------------------------------+
+
+An implementation of the VMBus relay that offers the Confidential VMBus
+channels is available in the OpenVMM project as a part of the OpenHCL
+paravisor. Please refer to
+
+  * https://openvmm.dev/, and
+  * https://github.com/microsoft/openvmm
+
+for more information about the OpenHCL paravisor.
+
+A guest that is running with a paravisor must determine at runtime if
+Confidential VMBus is supported by the current paravisor.The x86_64-specific
+approach relies on the CPUID Virtualization Stack leaf; the ARM64 implementation
+is expected to support the Confidential VMBus unconditionally when running
+the ARM CCA guests.
+
+Confidential VMBus is a characteristic of the VMBus connection as a whole,
+and of each VMBus channel that is created. When a Confidential VMBus
+connection is established, the paravisor provides the guest the message-passing
+path that is used for VMBus device creation and deletion, and it provides a
+per-CPU synthetic interrupt controller (SynIC) just like the SynIC that is
+offered by the Hyper-V host. Each VMBus device that is offered to the guest
+indicates the degree to which it participates in Confidential VMBus. The offer
+indicates if the device uses encrypted ring buffers, and if the device uses
+encrypted memory for DMA that is done outside the ring buffer. These settings
+may be different for different devices using the same Confidential VMBus
+connection.
+
+Although these settings are separate, in practice it'll always be encrypted
+ring buffer only, or both encrypted ring buffer and external data. If a channel
+is offered by the paravisor with confidential VMBus, the ring buffer can always
+be encrypted since it's strictly for communication between the VTL2 paravisor
+and the VTL0 guest. However, other memory regions are often used for e.g. DMA,
+so they need to be accessible by the underlying hardware, and must be
+unencrypted (unless the device supports encrypted memory). Currently, there are
+not any VSPs in OpenHCL that support encrypted external memory, but future
+versions are expected to enable this capability.
+
+Because some devices on a Confidential VMBus may require decrypted ring buffers
+and DMA transfers, the guest must interact with two SynICs -- the one provided
+by the paravisor and the one provided by the Hyper-V host when Confidential
+VMBus is not offered. Interrupts are always signaled by the paravisor SynIC,
+but the guest must check for messages and for channel interrupts on both SynICs.
+
+In the case of a confidential VMBus, regular SynIC access by the guest is
+intercepted by the paravisor (this includes various MSRs such as the SIMP and
+SIEFP, as well as hypercalls like HvPostMessage and HvSignalEvent). If the
+guest actually wants to communicate with the hypervisor, it has to use special
+mechanisms (GHCB page on SNP, or tdcall on TDX). Messages can be of either
+kind: with confidential VMBus, messages use the paravisor SynIC, and if the
+guest chose to communicate directly to the hypervisor, they use the hypervisor
+SynIC. For interrupt signaling, some channels may be running on the host
+(non-confidential, using the VMBus relay) and use the hypervisor SynIC, and
+some on the paravisor and use its SynIC. The RelIDs are coordinated by the
+OpenHCL VMBus server and are guaranteed to be unique regardless of whether
+the channel originated on the host or the paravisor.
+
 load_unaligned_zeropad()
 ------------------------
 When transitioning memory between encrypted and decrypted, the caller of
-- 
2.43.0

[PATCH hyperv-next v6 02/17] Drivers: hv: VMBus protocol version 6.0

[Roman Kisel]

The confidential VMBus is supported starting from the protocol
version 6.0 onwards.

Provide the required definitions. No functional changes.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/hyperv_vmbus.h   |  2 ++
 drivers/hv/vmbus_drv.c      | 12 +++++++
 include/hyperv/hvgdk_mini.h |  1 +
 include/linux/hyperv.h      | 69 +++++++++++++++++++++++++++----------
 4 files changed, 65 insertions(+), 19 deletions(-)

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 0b450e53161e..4a01797d4851 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -333,6 +333,8 @@ extern const struct vmbus_channel_message_table_entry
 
 /* General vmbus interface */
 
+bool vmbus_is_confidential(void);
+
 struct hv_device *vmbus_device_create(const guid_t *type,
 				      const guid_t *instance,
 				      struct vmbus_channel *channel);
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 69591dc7bad2..3c414560fa5f 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -56,6 +56,18 @@ static long __percpu *vmbus_evt;
 int vmbus_irq;
 int vmbus_interrupt;
 
+/*
+ * If the Confidential VMBus is used, the data on the "wire" is not
+ * visible to either the host or the hypervisor.
+ */
+static bool is_confidential;
+
+bool vmbus_is_confidential(void)
+{
+	return is_confidential;
+}
+EXPORT_SYMBOL_GPL(vmbus_is_confidential);
+
 /*
  * The panic notifier below is responsible solely for unloading the
  * vmbus connection, which is necessary in a panic event.
diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
index 77abddfc750e..7f730a0e54e6 100644
--- a/include/hyperv/hvgdk_mini.h
+++ b/include/hyperv/hvgdk_mini.h
@@ -260,6 +260,7 @@ union hv_hypervisor_version_info {
 #define HYPERV_CPUID_VIRT_STACK_PROPERTIES	 0x40000082
 /* Support for the extended IOAPIC RTE format */
 #define HYPERV_VS_PROPERTIES_EAX_EXTENDED_IOAPIC_RTE	 BIT(2)
+#define HYPERV_VS_PROPERTIES_EAX_CONFIDENTIAL_VMBUS_AVAILABLE	 BIT(3)
 
 #define HYPERV_HYPERVISOR_PRESENT_BIT		 0x80000000
 #define HYPERV_CPUID_MIN			 0x40000005
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 59826c89171c..dfc516c1c719 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -265,16 +265,18 @@ static inline u32 hv_get_avail_to_write_percent(
  * Linux kernel.
  */
 
-#define VERSION_WS2008  ((0 << 16) | (13))
-#define VERSION_WIN7    ((1 << 16) | (1))
-#define VERSION_WIN8    ((2 << 16) | (4))
-#define VERSION_WIN8_1    ((3 << 16) | (0))
-#define VERSION_WIN10 ((4 << 16) | (0))
-#define VERSION_WIN10_V4_1 ((4 << 16) | (1))
-#define VERSION_WIN10_V5 ((5 << 16) | (0))
-#define VERSION_WIN10_V5_1 ((5 << 16) | (1))
-#define VERSION_WIN10_V5_2 ((5 << 16) | (2))
-#define VERSION_WIN10_V5_3 ((5 << 16) | (3))
+#define VMBUS_MAKE_VERSION(MAJ, MIN)	((((u32)MAJ) << 16) | (MIN))
+#define VERSION_WS2008					VMBUS_MAKE_VERSION(0, 13)
+#define VERSION_WIN7					VMBUS_MAKE_VERSION(1, 1)
+#define VERSION_WIN8					VMBUS_MAKE_VERSION(2, 4)
+#define VERSION_WIN8_1					VMBUS_MAKE_VERSION(3, 0)
+#define VERSION_WIN10					VMBUS_MAKE_VERSION(4, 0)
+#define VERSION_WIN10_V4_1				VMBUS_MAKE_VERSION(4, 1)
+#define VERSION_WIN10_V5				VMBUS_MAKE_VERSION(5, 0)
+#define VERSION_WIN10_V5_1				VMBUS_MAKE_VERSION(5, 1)
+#define VERSION_WIN10_V5_2				VMBUS_MAKE_VERSION(5, 2)
+#define VERSION_WIN10_V5_3				VMBUS_MAKE_VERSION(5, 3)
+#define VERSION_WIN10_V6_0				VMBUS_MAKE_VERSION(6, 0)
 
 /* Make maximum size of pipe payload of 16K */
 #define MAX_PIPE_DATA_PAYLOAD		(sizeof(u8) * 16384)
@@ -335,14 +337,22 @@ struct vmbus_channel_offer {
 } __packed;
 
 /* Server Flags */
-#define VMBUS_CHANNEL_ENUMERATE_DEVICE_INTERFACE	1
-#define VMBUS_CHANNEL_SERVER_SUPPORTS_TRANSFER_PAGES	2
-#define VMBUS_CHANNEL_SERVER_SUPPORTS_GPADLS		4
-#define VMBUS_CHANNEL_NAMED_PIPE_MODE			0x10
-#define VMBUS_CHANNEL_LOOPBACK_OFFER			0x100
-#define VMBUS_CHANNEL_PARENT_OFFER			0x200
-#define VMBUS_CHANNEL_REQUEST_MONITORED_NOTIFICATION	0x400
-#define VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER		0x2000
+#define VMBUS_CHANNEL_ENUMERATE_DEVICE_INTERFACE		0x0001
+/*
+ * This flag indicates that the channel is offered by the paravisor, and must
+ * use encrypted memory for the channel ring buffer.
+ */
+#define VMBUS_CHANNEL_CONFIDENTIAL_RING_BUFFER			0x0002
+/*
+ * This flag indicates that the channel is offered by the paravisor, and must
+ * use encrypted memory for GPA direct packets and additional GPADLs.
+ */
+#define VMBUS_CHANNEL_CONFIDENTIAL_EXTERNAL_MEMORY		0x0004
+#define VMBUS_CHANNEL_NAMED_PIPE_MODE					0x0010
+#define VMBUS_CHANNEL_LOOPBACK_OFFER					0x0100
+#define VMBUS_CHANNEL_PARENT_OFFER						0x0200
+#define VMBUS_CHANNEL_REQUEST_MONITORED_NOTIFICATION	0x0400
+#define VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER				0x2000
 
 struct vmpacket_descriptor {
 	u16 type;
@@ -621,6 +631,12 @@ struct vmbus_channel_relid_released {
 	u32 child_relid;
 } __packed;
 
+/*
+ * Used by the paravisor only, means that the encrypted ring buffers and
+ * the encrypted external memory are supported
+ */
+#define VMBUS_FEATURE_FLAG_CONFIDENTIAL_CHANNELS	0x10
+
 struct vmbus_channel_initiate_contact {
 	struct vmbus_channel_message_header header;
 	u32 vmbus_version_requested;
@@ -630,7 +646,8 @@ struct vmbus_channel_initiate_contact {
 		struct {
 			u8	msg_sint;
 			u8	msg_vtl;
-			u8	reserved[6];
+			u8	reserved[2];
+			u32 feature_flags; /* VMBus version 6.0 */
 		};
 	};
 	u64 monitor_page1;
@@ -1003,6 +1020,10 @@ struct vmbus_channel {
 
 	/* boolean to control visibility of sysfs for ring buffer */
 	bool ring_sysfs_visible;
+	/* The ring buffer is encrypted */
+	bool co_ring_buffer;
+	/* The external memory is encrypted */
+	bool co_external_memory;
 };
 
 #define lock_requestor(channel, flags)					\
@@ -1027,6 +1048,16 @@ u64 vmbus_request_addr_match(struct vmbus_channel *channel, u64 trans_id,
 			     u64 rqst_addr);
 u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id);
 
+static inline bool is_co_ring_buffer(const struct vmbus_channel_offer_channel *o)
+{
+	return !!(o->offer.chn_flags & VMBUS_CHANNEL_CONFIDENTIAL_RING_BUFFER);
+}
+
+static inline bool is_co_external_memory(const struct vmbus_channel_offer_channel *o)
+{
+	return !!(o->offer.chn_flags & VMBUS_CHANNEL_CONFIDENTIAL_EXTERNAL_MEMORY);
+}
+
 static inline bool is_hvsock_offer(const struct vmbus_channel_offer_channel *o)
 {
 	return !!(o->offer.chn_flags & VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER);
-- 
2.43.0

[PATCH hyperv-next v6 03/17] arch/x86: mshyperv: Discover Confidential VMBus availability

[Roman Kisel]

Confidential VMBus requires enabling paravisor SynIC, and
the x86_64 guest has to inspect the Virtualization Stack (VS)
CPUID leaf to see if Confidential VMBus is available. If it is,
the guest shall enable the paravisor SynIC.

Read the relevant data from the VS CPUID leaf. Refactor the
code to avoid repeating CPUID and add flags to the struct
ms_hyperv_info. For ARM64, the flag for Confidential VMBus
is not set which provides the desired behaviour for now as
it is not available on ARM64 just yet. Once ARM64 CCA guests
are supported, this flag will be set unconditionally when
running such a guest.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 28 +++++++++++++++-------------
 include/asm-generic/mshyperv.h |  2 ++
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 25773af116bc..57163c7a000f 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -434,7 +434,7 @@ EXPORT_SYMBOL_GPL(hv_get_hypervisor_version);
 
 static void __init ms_hyperv_init_platform(void)
 {
-	int hv_max_functions_eax;
+	int hv_max_functions_eax, eax;
 
 #ifdef CONFIG_PARAVIRT
 	pv_info.name = "Hyper-V";
@@ -469,6 +469,19 @@ static void __init ms_hyperv_init_platform(void)
 		pr_info("Hyper-V: running on a nested hypervisor\n");
 	}
 
+	/*
+	 * There is no check against the max function for HYPERV_CPUID_VIRT_STACK_* CPUID
+	 * leaves as the hypervisor doesn't handle them. Even a nested root partition (L2
+	 * root) will not get them because the nested (L1) hypervisor filters them out.
+	 * These are handled through intercept processing by the Windows Hyper-V stack
+	 * or the paravisor.
+	 */
+	eax = cpuid_eax(HYPERV_CPUID_VIRT_STACK_PROPERTIES);
+	ms_hyperv.confidential_vmbus_available =
+		eax & HYPERV_VS_PROPERTIES_EAX_CONFIDENTIAL_VMBUS_AVAILABLE;
+	ms_hyperv.msi_ext_dest_id =
+		eax & HYPERV_VS_PROPERTIES_EAX_EXTENDED_IOAPIC_RTE;
+
 	if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
 	    ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
 		x86_platform.calibrate_tsc = hv_get_tsc_khz;
@@ -668,21 +681,10 @@ static bool __init ms_hyperv_x2apic_available(void)
  * pci-hyperv host bridge.
  *
  * Note: for a Hyper-V root partition, this will always return false.
- * The hypervisor doesn't expose these HYPERV_CPUID_VIRT_STACK_* cpuids by
- * default, they are implemented as intercepts by the Windows Hyper-V stack.
- * Even a nested root partition (L2 root) will not get them because the
- * nested (L1) hypervisor filters them out.
  */
 static bool __init ms_hyperv_msi_ext_dest_id(void)
 {
-	u32 eax;
-
-	eax = cpuid_eax(HYPERV_CPUID_VIRT_STACK_INTERFACE);
-	if (eax != HYPERV_VS_INTERFACE_EAX_SIGNATURE)
-		return false;
-
-	eax = cpuid_eax(HYPERV_CPUID_VIRT_STACK_PROPERTIES);
-	return eax & HYPERV_VS_PROPERTIES_EAX_EXTENDED_IOAPIC_RTE;
+	return ms_hyperv.msi_ext_dest_id;
 }
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 64ba6bc807d9..9049a9617324 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -62,6 +62,8 @@ struct ms_hyperv_info {
 		};
 	};
 	u64 shared_gpa_boundary;
+	bool msi_ext_dest_id;
+	bool confidential_vmbus_available;
 };
 extern struct ms_hyperv_info ms_hyperv;
 extern bool hv_nested;
-- 
2.43.0

[PATCH hyperv-next v6 04/17] arch: hyperv: Get/set SynIC synth.registers via paravisor

[Roman Kisel]

The existing Hyper-V wrappers for getting and setting MSRs are
hv_get/set_msr(). Via hv_get/set_non_nested_msr(), they detect
when running in a CoCo VM with a paravisor, and use the TDX or
SNP guest-host communication protocol to bypass the paravisor
and go directly to the host hypervisor for SynIC MSRs. The "set"
function also implements the required special handling for the
SINT MSRs.

Provide functions that allow manipulating the SynIC registers
through the paravisor. Move vmbus_signal_eom() to a more
appropriate location (which also avoids breaking KVM).

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 20 ++++++++++++++++
 drivers/hv/hv_common.c         | 11 +++++++++
 drivers/hv/hyperv_vmbus.h      | 44 ++++++++++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h | 42 ++------------------------------
 4 files changed, 77 insertions(+), 40 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 57163c7a000f..af5a3bbbca9f 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -90,6 +90,26 @@ void hv_set_non_nested_msr(unsigned int reg, u64 value)
 }
 EXPORT_SYMBOL_GPL(hv_set_non_nested_msr);
 
+/*
+ * Get the SynIC register value from the paravisor.
+ */
+u64 hv_para_get_synic_register(unsigned int reg)
+{
+	if (WARN_ON(!ms_hyperv.paravisor_present || !hv_is_synic_msr(reg)))
+		return ~0ULL;
+	return native_read_msr(reg);
+}
+
+/*
+ * Set the SynIC register value with the paravisor.
+ */
+void hv_para_set_synic_register(unsigned int reg, u64 val)
+{
+	if (WARN_ON(!ms_hyperv.paravisor_present || !hv_is_synic_msr(reg)))
+		return;
+	native_write_msr(reg, val);
+}
+
 u64 hv_get_msr(unsigned int reg)
 {
 	if (hv_nested)
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index e109a620c83f..8756ca834546 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -716,6 +716,17 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
 }
 EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
 
+u64 __weak hv_para_get_synic_register(unsigned int reg)
+{
+	return ~0ULL;
+}
+EXPORT_SYMBOL_GPL(hv_para_get_synic_register);
+
+void __weak hv_para_set_synic_register(unsigned int reg, u64 val)
+{
+}
+EXPORT_SYMBOL_GPL(hv_para_set_synic_register);
+
 void hv_identify_partition_type(void)
 {
 	/* Assume guest role */
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 4a01797d4851..9ac6f5520287 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -15,6 +15,7 @@
 #include <linux/list.h>
 #include <linux/bitops.h>
 #include <asm/sync_bitops.h>
+#include <asm/mshyperv.h>
 #include <linux/atomic.h>
 #include <linux/hyperv.h>
 #include <linux/interrupt.h>
@@ -335,6 +336,49 @@ extern const struct vmbus_channel_message_table_entry
 
 bool vmbus_is_confidential(void);
 
+#if IS_ENABLED(CONFIG_HYPERV_VMBUS)
+/* Free the message slot and signal end-of-message if required */
+static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
+{
+	/*
+	 * On crash we're reading some other CPU's message page and we need
+	 * to be careful: this other CPU may already had cleared the header
+	 * and the host may already had delivered some other message there.
+	 * In case we blindly write msg->header.message_type we're going
+	 * to lose it. We can still lose a message of the same type but
+	 * we count on the fact that there can only be one
+	 * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages
+	 * on crash.
+	 */
+	if (cmpxchg(&msg->header.message_type, old_msg_type,
+		    HVMSG_NONE) != old_msg_type)
+		return;
+
+	/*
+	 * The cmxchg() above does an implicit memory barrier to
+	 * ensure the write to MessageType (ie set to
+	 * HVMSG_NONE) happens before we read the
+	 * MessagePending and EOMing. Otherwise, the EOMing
+	 * will not deliver any more messages since there is
+	 * no empty slot
+	 */
+	if (msg->header.message_flags.msg_pending) {
+		/*
+		 * This will cause message queue rescan to
+		 * possibly deliver another msg from the
+		 * hypervisor
+		 */
+		if (vmbus_is_confidential())
+			hv_para_set_synic_register(HV_MSR_EOM, 0);
+		else
+			hv_set_msr(HV_MSR_EOM, 0);
+	}
+}
+
+extern int vmbus_interrupt;
+extern int vmbus_irq;
+#endif /* CONFIG_HYPERV_VMBUS */
+
 struct hv_device *vmbus_device_create(const guid_t *type,
 				      const guid_t *instance,
 				      struct vmbus_channel *channel);
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 9049a9617324..c010059f1518 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -165,46 +165,6 @@ static inline u64 hv_generate_guest_id(u64 kernel_version)
 	return guest_id;
 }
 
-#if IS_ENABLED(CONFIG_HYPERV_VMBUS)
-/* Free the message slot and signal end-of-message if required */
-static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
-{
-	/*
-	 * On crash we're reading some other CPU's message page and we need
-	 * to be careful: this other CPU may already had cleared the header
-	 * and the host may already had delivered some other message there.
-	 * In case we blindly write msg->header.message_type we're going
-	 * to lose it. We can still lose a message of the same type but
-	 * we count on the fact that there can only be one
-	 * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages
-	 * on crash.
-	 */
-	if (cmpxchg(&msg->header.message_type, old_msg_type,
-		    HVMSG_NONE) != old_msg_type)
-		return;
-
-	/*
-	 * The cmxchg() above does an implicit memory barrier to
-	 * ensure the write to MessageType (ie set to
-	 * HVMSG_NONE) happens before we read the
-	 * MessagePending and EOMing. Otherwise, the EOMing
-	 * will not deliver any more messages since there is
-	 * no empty slot
-	 */
-	if (msg->header.message_flags.msg_pending) {
-		/*
-		 * This will cause message queue rescan to
-		 * possibly deliver another msg from the
-		 * hypervisor
-		 */
-		hv_set_msr(HV_MSR_EOM, 0);
-	}
-}
-
-extern int vmbus_interrupt;
-extern int vmbus_irq;
-#endif /* CONFIG_HYPERV_VMBUS */
-
 int hv_get_hypervisor_version(union hv_hypervisor_version_info *info);
 
 void hv_setup_vmbus_handler(void (*handler)(void));
@@ -338,6 +298,8 @@ bool hv_is_isolation_supported(void);
 bool hv_isolation_type_snp(void);
 u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
 u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
+u64 hv_para_get_synic_register(unsigned int reg);
+void hv_para_set_synic_register(unsigned int reg, u64 val);
 void hyperv_cleanup(void);
 bool hv_query_ext_cap(u64 cap_query);
 void hv_setup_dma_ops(struct device *dev, bool coherent);
-- 
2.43.0

[PATCH hyperv-next v6 05/17] arch/x86: mshyperv: Trap on access for some synthetic MSRs

[Roman Kisel]

hv_set_non_nested_msr() has special handling for SINT MSRs
when a paravisor is present. In addition to updating the MSR on the
host, the mirror MSR in the paravisor is updated, including with the
proxy bit. But with Confidential VMBus, the proxy bit must not be
used, so add a special case to skip it.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 29 +++++++++++++++++++++++++----
 drivers/hv/hv_common.c         |  5 +++++
 include/asm-generic/mshyperv.h |  1 +
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index af5a3bbbca9f..b410b930938a 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -28,6 +28,7 @@
 #include <asm/apic.h>
 #include <asm/timer.h>
 #include <asm/reboot.h>
+#include <asm/msr.h>
 #include <asm/nmi.h>
 #include <clocksource/hyperv_timer.h>
 #include <asm/msr.h>
@@ -38,6 +39,12 @@
 bool hv_nested;
 struct ms_hyperv_info ms_hyperv;
 
+/*
+ * When running with the paravisor, controls proxying the synthetic interrupts
+ * from the host
+ */
+static bool hv_para_sint_proxy;
+
 /* Used in modules via hv_do_hypercall(): see arch/x86/include/asm/mshyperv.h */
 bool hyperv_paravisor_present __ro_after_init;
 EXPORT_SYMBOL_GPL(hyperv_paravisor_present);
@@ -79,17 +86,31 @@ EXPORT_SYMBOL_GPL(hv_get_non_nested_msr);
 void hv_set_non_nested_msr(unsigned int reg, u64 value)
 {
 	if (hv_is_synic_msr(reg) && ms_hyperv.paravisor_present) {
+		/* The hypervisor will get the intercept. */
 		hv_ivm_msr_write(reg, value);
 
-		/* Write proxy bit via wrmsl instruction */
-		if (hv_is_sint_msr(reg))
-			wrmsrq(reg, value | 1 << 20);
+		/* Using wrmsrq so the following goes to the paravisor. */
+		if (hv_is_sint_msr(reg)) {
+			union hv_synic_sint sint = { .as_uint64 = value };
+
+			sint.proxy = hv_para_sint_proxy;
+			native_wrmsrq(reg, sint.as_uint64);
+		}
 	} else {
-		wrmsrq(reg, value);
+		native_wrmsrq(reg, value);
 	}
 }
 EXPORT_SYMBOL_GPL(hv_set_non_nested_msr);
 
+/*
+ * Enable or disable proxying synthetic interrupts
+ * to the paravisor.
+ */
+void hv_para_set_sint_proxy(bool enable)
+{
+	hv_para_sint_proxy = enable;
+}
+
 /*
  * Get the SynIC register value from the paravisor.
  */
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 8756ca834546..1a5c7a358971 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -716,6 +716,11 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
 }
 EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
 
+void __weak hv_para_set_sint_proxy(bool enable)
+{
+}
+EXPORT_SYMBOL_GPL(hv_para_set_sint_proxy);
+
 u64 __weak hv_para_get_synic_register(unsigned int reg)
 {
 	return ~0ULL;
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index c010059f1518..3955ba6d60b8 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -298,6 +298,7 @@ bool hv_is_isolation_supported(void);
 bool hv_isolation_type_snp(void);
 u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
 u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
+void hv_para_set_sint_proxy(bool enable);
 u64 hv_para_get_synic_register(unsigned int reg);
 void hv_para_set_synic_register(unsigned int reg, u64 val);
 void hyperv_cleanup(void);
-- 
2.43.0

[PATCH hyperv-next v6 06/17] Drivers: hv: Rename fields for SynIC message and event pages

[Roman Kisel]

Confidential VMBus requires interacting with two SynICs -- one
provided by the host hypervisor, and one provided by the paravisor.
Each SynIC requires its own message and event pages.

Rename the existing host-accessible SynIC message and event pages
with the "hyp_" prefix to clearly distinguish them from the paravisor
ones. The field name is also changed in mshv_root.* for consistency.

No functional changes.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/channel_mgmt.c |  6 ++--
 drivers/hv/hv.c           | 66 +++++++++++++++++++--------------------
 drivers/hv/hyperv_vmbus.h |  4 +--
 drivers/hv/mshv_root.h    |  2 +-
 drivers/hv/mshv_synic.c   |  6 ++--
 drivers/hv/vmbus_drv.c    |  6 ++--
 6 files changed, 45 insertions(+), 45 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 65dd299e2944..1a33c6944b3c 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -844,14 +844,14 @@ static void vmbus_wait_for_unload(void)
 				= per_cpu_ptr(hv_context.cpu_context, cpu);
 
 			/*
-			 * In a CoCo VM the synic_message_page is not allocated
+			 * In a CoCo VM the hyp_synic_message_page is not allocated
 			 * in hv_synic_alloc(). Instead it is set/cleared in
 			 * hv_synic_enable_regs() and hv_synic_disable_regs()
 			 * such that it is set only when the CPU is online. If
 			 * not all present CPUs are online, the message page
 			 * might be NULL, so skip such CPUs.
 			 */
-			page_addr = hv_cpu->synic_message_page;
+			page_addr = hv_cpu->hyp_synic_message_page;
 			if (!page_addr)
 				continue;
 
@@ -892,7 +892,7 @@ static void vmbus_wait_for_unload(void)
 		struct hv_per_cpu_context *hv_cpu
 			= per_cpu_ptr(hv_context.cpu_context, cpu);
 
-		page_addr = hv_cpu->synic_message_page;
+		page_addr = hv_cpu->hyp_synic_message_page;
 		if (!page_addr)
 			continue;
 
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index b14c5f9e0ef2..b7419d0fad1d 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -147,20 +147,20 @@ int hv_synic_alloc(void)
 		 * Skip these pages allocation here.
 		 */
 		if (!ms_hyperv.paravisor_present && !hv_root_partition()) {
-			hv_cpu->synic_message_page =
+			hv_cpu->hyp_synic_message_page =
 				(void *)get_zeroed_page(GFP_ATOMIC);
-			if (!hv_cpu->synic_message_page) {
+			if (!hv_cpu->hyp_synic_message_page) {
 				pr_err("Unable to allocate SYNIC message page\n");
 				goto err;
 			}
 
-			hv_cpu->synic_event_page =
+			hv_cpu->hyp_synic_event_page =
 				(void *)get_zeroed_page(GFP_ATOMIC);
-			if (!hv_cpu->synic_event_page) {
+			if (!hv_cpu->hyp_synic_event_page) {
 				pr_err("Unable to allocate SYNIC event page\n");
 
-				free_page((unsigned long)hv_cpu->synic_message_page);
-				hv_cpu->synic_message_page = NULL;
+				free_page((unsigned long)hv_cpu->hyp_synic_message_page);
+				hv_cpu->hyp_synic_message_page = NULL;
 				goto err;
 			}
 		}
@@ -168,30 +168,30 @@ int hv_synic_alloc(void)
 		if (!ms_hyperv.paravisor_present &&
 		    (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
 			ret = set_memory_decrypted((unsigned long)
-				hv_cpu->synic_message_page, 1);
+				hv_cpu->hyp_synic_message_page, 1);
 			if (ret) {
 				pr_err("Failed to decrypt SYNIC msg page: %d\n", ret);
-				hv_cpu->synic_message_page = NULL;
+				hv_cpu->hyp_synic_message_page = NULL;
 
 				/*
 				 * Free the event page here so that hv_synic_free()
 				 * won't later try to re-encrypt it.
 				 */
-				free_page((unsigned long)hv_cpu->synic_event_page);
-				hv_cpu->synic_event_page = NULL;
+				free_page((unsigned long)hv_cpu->hyp_synic_event_page);
+				hv_cpu->hyp_synic_event_page = NULL;
 				goto err;
 			}
 
 			ret = set_memory_decrypted((unsigned long)
-				hv_cpu->synic_event_page, 1);
+				hv_cpu->hyp_synic_event_page, 1);
 			if (ret) {
 				pr_err("Failed to decrypt SYNIC event page: %d\n", ret);
-				hv_cpu->synic_event_page = NULL;
+				hv_cpu->hyp_synic_event_page = NULL;
 				goto err;
 			}
 
-			memset(hv_cpu->synic_message_page, 0, PAGE_SIZE);
-			memset(hv_cpu->synic_event_page, 0, PAGE_SIZE);
+			memset(hv_cpu->hyp_synic_message_page, 0, PAGE_SIZE);
+			memset(hv_cpu->hyp_synic_event_page, 0, PAGE_SIZE);
 		}
 	}
 
@@ -227,28 +227,28 @@ void hv_synic_free(void)
 
 		if (!ms_hyperv.paravisor_present &&
 		    (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
-			if (hv_cpu->synic_message_page) {
+			if (hv_cpu->hyp_synic_message_page) {
 				ret = set_memory_encrypted((unsigned long)
-					hv_cpu->synic_message_page, 1);
+					hv_cpu->hyp_synic_message_page, 1);
 				if (ret) {
 					pr_err("Failed to encrypt SYNIC msg page: %d\n", ret);
-					hv_cpu->synic_message_page = NULL;
+					hv_cpu->hyp_synic_message_page = NULL;
 				}
 			}
 
-			if (hv_cpu->synic_event_page) {
+			if (hv_cpu->hyp_synic_event_page) {
 				ret = set_memory_encrypted((unsigned long)
-					hv_cpu->synic_event_page, 1);
+					hv_cpu->hyp_synic_event_page, 1);
 				if (ret) {
 					pr_err("Failed to encrypt SYNIC event page: %d\n", ret);
-					hv_cpu->synic_event_page = NULL;
+					hv_cpu->hyp_synic_event_page = NULL;
 				}
 			}
 		}
 
 		free_page((unsigned long)hv_cpu->post_msg_page);
-		free_page((unsigned long)hv_cpu->synic_event_page);
-		free_page((unsigned long)hv_cpu->synic_message_page);
+		free_page((unsigned long)hv_cpu->hyp_synic_event_page);
+		free_page((unsigned long)hv_cpu->hyp_synic_message_page);
 	}
 
 	kfree(hv_context.hv_numa_map);
@@ -278,12 +278,12 @@ void hv_synic_enable_regs(unsigned int cpu)
 		/* Mask out vTOM bit. ioremap_cache() maps decrypted */
 		u64 base = (simp.base_simp_gpa << HV_HYP_PAGE_SHIFT) &
 				~ms_hyperv.shared_gpa_boundary;
-		hv_cpu->synic_message_page =
+		hv_cpu->hyp_synic_message_page =
 			(void *)ioremap_cache(base, HV_HYP_PAGE_SIZE);
-		if (!hv_cpu->synic_message_page)
+		if (!hv_cpu->hyp_synic_message_page)
 			pr_err("Fail to map synic message page.\n");
 	} else {
-		simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
+		simp.base_simp_gpa = virt_to_phys(hv_cpu->hyp_synic_message_page)
 			>> HV_HYP_PAGE_SHIFT;
 	}
 
@@ -297,12 +297,12 @@ void hv_synic_enable_regs(unsigned int cpu)
 		/* Mask out vTOM bit. ioremap_cache() maps decrypted */
 		u64 base = (siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT) &
 				~ms_hyperv.shared_gpa_boundary;
-		hv_cpu->synic_event_page =
+		hv_cpu->hyp_synic_event_page =
 			(void *)ioremap_cache(base, HV_HYP_PAGE_SIZE);
-		if (!hv_cpu->synic_event_page)
+		if (!hv_cpu->hyp_synic_event_page)
 			pr_err("Fail to map synic event page.\n");
 	} else {
-		siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
+		siefp.base_siefp_gpa = virt_to_phys(hv_cpu->hyp_synic_event_page)
 			>> HV_HYP_PAGE_SHIFT;
 	}
 
@@ -360,8 +360,8 @@ void hv_synic_disable_regs(unsigned int cpu)
 	 */
 	simp.simp_enabled = 0;
 	if (ms_hyperv.paravisor_present || hv_root_partition()) {
-		iounmap(hv_cpu->synic_message_page);
-		hv_cpu->synic_message_page = NULL;
+		iounmap(hv_cpu->hyp_synic_message_page);
+		hv_cpu->hyp_synic_message_page = NULL;
 	} else {
 		simp.base_simp_gpa = 0;
 	}
@@ -372,8 +372,8 @@ void hv_synic_disable_regs(unsigned int cpu)
 	siefp.siefp_enabled = 0;
 
 	if (ms_hyperv.paravisor_present || hv_root_partition()) {
-		iounmap(hv_cpu->synic_event_page);
-		hv_cpu->synic_event_page = NULL;
+		iounmap(hv_cpu->hyp_synic_event_page);
+		hv_cpu->hyp_synic_event_page = NULL;
 	} else {
 		siefp.base_siefp_gpa = 0;
 	}
@@ -403,7 +403,7 @@ static bool hv_synic_event_pending(void)
 {
 	struct hv_per_cpu_context *hv_cpu = this_cpu_ptr(hv_context.cpu_context);
 	union hv_synic_event_flags *event =
-		(union hv_synic_event_flags *)hv_cpu->synic_event_page + VMBUS_MESSAGE_SINT;
+		(union hv_synic_event_flags *)hv_cpu->hyp_synic_event_page + VMBUS_MESSAGE_SINT;
 	unsigned long *recv_int_page = event->flags; /* assumes VMBus version >= VERSION_WIN8 */
 	bool pending;
 	u32 relid;
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 9ac6f5520287..d593af45a5b2 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -121,8 +121,8 @@ enum {
  * Per cpu state for channel handling
  */
 struct hv_per_cpu_context {
-	void *synic_message_page;
-	void *synic_event_page;
+	void *hyp_synic_message_page;
+	void *hyp_synic_event_page;
 
 	/*
 	 * The page is only used in hv_post_message() for a TDX VM (with the
diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
index e3931b0f1269..db6b42db2fdc 100644
--- a/drivers/hv/mshv_root.h
+++ b/drivers/hv/mshv_root.h
@@ -169,7 +169,7 @@ struct mshv_girq_routing_table {
 };
 
 struct hv_synic_pages {
-	struct hv_message_page *synic_message_page;
+	struct hv_message_page *hyp_synic_message_page;
 	struct hv_synic_event_flags_page *synic_event_flags_page;
 	struct hv_synic_event_ring_page *synic_event_ring_page;
 };
diff --git a/drivers/hv/mshv_synic.c b/drivers/hv/mshv_synic.c
index e6b6381b7c36..f8b0337cdc82 100644
--- a/drivers/hv/mshv_synic.c
+++ b/drivers/hv/mshv_synic.c
@@ -394,7 +394,7 @@ mshv_intercept_isr(struct hv_message *msg)
 void mshv_isr(void)
 {
 	struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
-	struct hv_message_page **msg_page = &spages->synic_message_page;
+	struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
 	struct hv_message *msg;
 	bool handled;
 
@@ -456,7 +456,7 @@ int mshv_synic_init(unsigned int cpu)
 #endif
 	union hv_synic_scontrol sctrl;
 	struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
-	struct hv_message_page **msg_page = &spages->synic_message_page;
+	struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
 	struct hv_synic_event_flags_page **event_flags_page =
 			&spages->synic_event_flags_page;
 	struct hv_synic_event_ring_page **event_ring_page =
@@ -550,7 +550,7 @@ int mshv_synic_cleanup(unsigned int cpu)
 	union hv_synic_sirbp sirbp;
 	union hv_synic_scontrol sctrl;
 	struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
-	struct hv_message_page **msg_page = &spages->synic_message_page;
+	struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
 	struct hv_synic_event_flags_page **event_flags_page =
 		&spages->synic_event_flags_page;
 	struct hv_synic_event_ring_page **event_ring_page =
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 3c414560fa5f..e12f0ba0701f 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1060,7 +1060,7 @@ static void vmbus_onmessage_work(struct work_struct *work)
 void vmbus_on_msg_dpc(unsigned long data)
 {
 	struct hv_per_cpu_context *hv_cpu = (void *)data;
-	void *page_addr = hv_cpu->synic_message_page;
+	void *page_addr = hv_cpu->hyp_synic_message_page;
 	struct hv_message msg_copy, *msg = (struct hv_message *)page_addr +
 				  VMBUS_MESSAGE_SINT;
 	struct vmbus_channel_message_header *hdr;
@@ -1244,7 +1244,7 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
 	 * The event page can be directly checked to get the id of
 	 * the channel that has the interrupt pending.
 	 */
-	void *page_addr = hv_cpu->synic_event_page;
+	void *page_addr = hv_cpu->hyp_synic_event_page;
 	union hv_synic_event_flags *event
 		= (union hv_synic_event_flags *)page_addr +
 					 VMBUS_MESSAGE_SINT;
@@ -1327,7 +1327,7 @@ static void vmbus_isr(void)
 
 	vmbus_chan_sched(hv_cpu);
 
-	page_addr = hv_cpu->synic_message_page;
+	page_addr = hv_cpu->hyp_synic_message_page;
 	msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
 
 	/* Check if there are actual msgs to be processed */
-- 
2.43.0

[PATCH hyperv-next v6 07/17] Drivers: hv: Allocate the paravisor SynIC pages when required

[Roman Kisel]

Confidential VMBus requires interacting with two SynICs -- one
provided by the host hypervisor, and one provided by the paravisor.
Each SynIC requires its own message and event pages.

Refactor and extend the existing code to add allocating and freeing
the message and event pages for the paravisor SynIC when it is
present.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/hv.c           | 184 +++++++++++++++++++-------------------
 drivers/hv/hyperv_vmbus.h |  18 ++++
 2 files changed, 112 insertions(+), 90 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index b7419d0fad1d..90db1e17582d 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -96,10 +96,70 @@ int hv_post_message(union hv_connection_id connection_id,
 	return hv_result(status);
 }
 
+static int hv_alloc_page(void **page, bool decrypt, const char *note)
+{
+	int ret = 0;
+
+	/*
+	 * After the page changes its encryption status, its contents might
+	 * appear scrambled on some hardware. Thus `get_zeroed_page` would
+	 * zero the page out in vain, so do that explicitly exactly once.
+	 *
+	 * By default, the page is allocated encrypted in a CoCo VM.
+	 */
+	*page = (void *)__get_free_page(GFP_KERNEL);
+	if (!*page)
+		return -ENOMEM;
+
+	if (decrypt)
+		ret = set_memory_decrypted((unsigned long)*page, 1);
+	if (ret)
+		goto failed;
+
+	memset(*page, 0, PAGE_SIZE);
+	return 0;
+
+failed:
+	/*
+	 * Report the failure but don't put the page back on the free list as
+	 * its encryption status is unknown.
+	 */
+	pr_err("allocation failed for %s page, error %d, decrypted %d\n",
+		note, ret, decrypt);
+	*page = NULL;
+	return ret;
+}
+
+static int hv_free_page(void **page, bool encrypt, const char *note)
+{
+	int ret = 0;
+
+	if (!*page)
+		return 0;
+
+	if (encrypt)
+		ret = set_memory_encrypted((unsigned long)*page, 1);
+
+	/*
+	 * In the case of the failure, the page is leaked. Something is wrong,
+	 * prefer to lose the page with the unknown encryption status and stay afloat.
+	 */
+	if (ret)
+		pr_err("deallocation failed for %s page, error %d, encrypt %d\n",
+			note, ret, encrypt);
+	else
+		free_page((unsigned long)*page);
+
+	*page = NULL;
+
+	return ret;
+}
+
 int hv_synic_alloc(void)
 {
 	int cpu, ret = -ENOMEM;
 	struct hv_per_cpu_context *hv_cpu;
+	const bool decrypt = !vmbus_is_confidential();
 
 	/*
 	 * First, zero all per-cpu memory areas so hv_synic_free() can
@@ -125,73 +185,37 @@ int hv_synic_alloc(void)
 			     vmbus_on_msg_dpc, (unsigned long)hv_cpu);
 
 		if (ms_hyperv.paravisor_present && hv_isolation_type_tdx()) {
-			hv_cpu->post_msg_page = (void *)get_zeroed_page(GFP_ATOMIC);
-			if (!hv_cpu->post_msg_page) {
-				pr_err("Unable to allocate post msg page\n");
+			ret = hv_alloc_page(&hv_cpu->post_msg_page,
+				decrypt, "post msg");
+			if (ret)
 				goto err;
-			}
-
-			ret = set_memory_decrypted((unsigned long)hv_cpu->post_msg_page, 1);
-			if (ret) {
-				pr_err("Failed to decrypt post msg page: %d\n", ret);
-				/* Just leak the page, as it's unsafe to free the page. */
-				hv_cpu->post_msg_page = NULL;
-				goto err;
-			}
-
-			memset(hv_cpu->post_msg_page, 0, PAGE_SIZE);
 		}
 
 		/*
-		 * Synic message and event pages are allocated by paravisor.
-		 * Skip these pages allocation here.
+		 * If these SynIC pages are not allocated, SIEF and SIM pages
+		 * are configured using what the root partition or the paravisor
+		 * provides upon reading the SIEFP and SIMP registers.
 		 */
 		if (!ms_hyperv.paravisor_present && !hv_root_partition()) {
-			hv_cpu->hyp_synic_message_page =
-				(void *)get_zeroed_page(GFP_ATOMIC);
-			if (!hv_cpu->hyp_synic_message_page) {
-				pr_err("Unable to allocate SYNIC message page\n");
+			ret = hv_alloc_page(&hv_cpu->hyp_synic_message_page,
+				decrypt, "hypervisor SynIC msg");
+			if (ret)
 				goto err;
-			}
-
-			hv_cpu->hyp_synic_event_page =
-				(void *)get_zeroed_page(GFP_ATOMIC);
-			if (!hv_cpu->hyp_synic_event_page) {
-				pr_err("Unable to allocate SYNIC event page\n");
-
-				free_page((unsigned long)hv_cpu->hyp_synic_message_page);
-				hv_cpu->hyp_synic_message_page = NULL;
+			ret = hv_alloc_page(&hv_cpu->hyp_synic_event_page,
+				decrypt, "hypervisor SynIC event");
+			if (ret)
 				goto err;
-			}
 		}
 
-		if (!ms_hyperv.paravisor_present &&
-		    (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
-			ret = set_memory_decrypted((unsigned long)
-				hv_cpu->hyp_synic_message_page, 1);
-			if (ret) {
-				pr_err("Failed to decrypt SYNIC msg page: %d\n", ret);
-				hv_cpu->hyp_synic_message_page = NULL;
-
-				/*
-				 * Free the event page here so that hv_synic_free()
-				 * won't later try to re-encrypt it.
-				 */
-				free_page((unsigned long)hv_cpu->hyp_synic_event_page);
-				hv_cpu->hyp_synic_event_page = NULL;
+		if (vmbus_is_confidential()) {
+			ret = hv_alloc_page(&hv_cpu->para_synic_message_page,
+				false, "paravisor SynIC msg");
+			if (ret)
 				goto err;
-			}
-
-			ret = set_memory_decrypted((unsigned long)
-				hv_cpu->hyp_synic_event_page, 1);
-			if (ret) {
-				pr_err("Failed to decrypt SYNIC event page: %d\n", ret);
-				hv_cpu->hyp_synic_event_page = NULL;
+			ret = hv_alloc_page(&hv_cpu->para_synic_event_page,
+				false, "paravisor SynIC event");
+			if (ret)
 				goto err;
-			}
-
-			memset(hv_cpu->hyp_synic_message_page, 0, PAGE_SIZE);
-			memset(hv_cpu->hyp_synic_event_page, 0, PAGE_SIZE);
 		}
 	}
 
@@ -207,48 +231,28 @@ int hv_synic_alloc(void)
 
 void hv_synic_free(void)
 {
-	int cpu, ret;
+	int cpu;
+	const bool encrypt = !vmbus_is_confidential();
 
 	for_each_present_cpu(cpu) {
 		struct hv_per_cpu_context *hv_cpu =
 			per_cpu_ptr(hv_context.cpu_context, cpu);
 
-		/* It's better to leak the page if the encryption fails. */
-		if (ms_hyperv.paravisor_present && hv_isolation_type_tdx()) {
-			if (hv_cpu->post_msg_page) {
-				ret = set_memory_encrypted((unsigned long)
-					hv_cpu->post_msg_page, 1);
-				if (ret) {
-					pr_err("Failed to encrypt post msg page: %d\n", ret);
-					hv_cpu->post_msg_page = NULL;
-				}
-			}
+		if (ms_hyperv.paravisor_present && hv_isolation_type_tdx())
+			hv_free_page(&hv_cpu->post_msg_page,
+				encrypt, "post msg");
+		if (!ms_hyperv.paravisor_present && !hv_root_partition()) {
+			hv_free_page(&hv_cpu->hyp_synic_event_page,
+				encrypt, "hypervisor SynIC event");
+			hv_free_page(&hv_cpu->hyp_synic_message_page,
+				encrypt, "hypervisor SynIC msg");
 		}
-
-		if (!ms_hyperv.paravisor_present &&
-		    (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
-			if (hv_cpu->hyp_synic_message_page) {
-				ret = set_memory_encrypted((unsigned long)
-					hv_cpu->hyp_synic_message_page, 1);
-				if (ret) {
-					pr_err("Failed to encrypt SYNIC msg page: %d\n", ret);
-					hv_cpu->hyp_synic_message_page = NULL;
-				}
-			}
-
-			if (hv_cpu->hyp_synic_event_page) {
-				ret = set_memory_encrypted((unsigned long)
-					hv_cpu->hyp_synic_event_page, 1);
-				if (ret) {
-					pr_err("Failed to encrypt SYNIC event page: %d\n", ret);
-					hv_cpu->hyp_synic_event_page = NULL;
-				}
-			}
+		if (vmbus_is_confidential()) {
+			hv_free_page(&hv_cpu->para_synic_event_page,
+				false, "paravisor SynIC event");
+			hv_free_page(&hv_cpu->para_synic_message_page,
+				false, "paravisor SynIC msg");
 		}
-
-		free_page((unsigned long)hv_cpu->post_msg_page);
-		free_page((unsigned long)hv_cpu->hyp_synic_event_page);
-		free_page((unsigned long)hv_cpu->hyp_synic_message_page);
 	}
 
 	kfree(hv_context.hv_numa_map);
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index d593af45a5b2..3c70051c0431 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -121,8 +121,26 @@ enum {
  * Per cpu state for channel handling
  */
 struct hv_per_cpu_context {
+	/*
+	 * SynIC pages for communicating with the host.
+	 *
+	 * These pages are accessible to the host partition and the hypervisor.
+	 * They may be used for exchanging data with the host partition and the
+	 * hypervisor even when they aren't trusted yet the guest partition
+	 * must be prepared to handle the malicious behavior.
+	 */
 	void *hyp_synic_message_page;
 	void *hyp_synic_event_page;
+	/*
+	 * SynIC pages for communicating with the paravisor.
+	 *
+	 * These pages may be accessed from within the guest partition only in
+	 * CoCo VMs. Neither the host partition nor the hypervisor can access
+	 * these pages in that case; they are used for exchanging data with the
+	 * paravisor.
+	 */
+	void *para_synic_message_page;
+	void *para_synic_event_page;
 
 	/*
 	 * The page is only used in hv_post_message() for a TDX VM (with the
-- 
2.43.0

[PATCH hyperv-next v6 08/17] Drivers: hv: Post messages through the confidential VMBus if available

[Roman Kisel]

When the confidential VMBus is available, the guest should post
messages to the paravisor.

Update hv_post_message() to post messages to the paravisor rather than
through GHCB or TD calls.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/hv.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 90db1e17582d..b1085473778c 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -74,7 +74,11 @@ int hv_post_message(union hv_connection_id connection_id,
 	aligned_msg->payload_size = payload_size;
 	memcpy((void *)aligned_msg->payload, payload, payload_size);
 
-	if (ms_hyperv.paravisor_present) {
+	if (ms_hyperv.paravisor_present && !vmbus_is_confidential()) {
+		/*
+		 * If the VMBus isn't confidential, use the CoCo-specific
+		 * mechanism to communicate with the hypervisor.
+		 */
 		if (hv_isolation_type_tdx())
 			status = hv_tdx_hypercall(HVCALL_POST_MESSAGE,
 						  virt_to_phys(aligned_msg), 0);
@@ -88,6 +92,11 @@ int hv_post_message(union hv_connection_id connection_id,
 		u64 control = HVCALL_POST_MESSAGE;
 
 		control |= hv_nested ? HV_HYPERCALL_NESTED : 0;
+		/*
+		 * If there is no paravisor, this will go to the hypervisor.
+		 * In the Confidential VMBus case, there is the paravisor
+		 * to which this will trap.
+		 */
 		status = hv_do_hypercall(control, aligned_msg, NULL);
 	}
 
-- 
2.43.0

[PATCH hyperv-next v6 09/17] Drivers: hv: remove stale comment

[Roman Kisel]

The comment about the x2v shim is ancient and long since incorrect.

Remove the incorrect comment.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/hv.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index b1085473778c..95631c08a71f 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -268,11 +268,7 @@ void hv_synic_free(void)
 }
 
 /*
- * hv_synic_init - Initialize the Synthetic Interrupt Controller.
- *
- * If it is already initialized by another entity (ie x2v shim), we need to
- * retrieve the initialized message and event pages.  Otherwise, we create and
- * initialize the message and event pages.
+ * hv_synic_enable_regs - Initialize the Synthetic Interrupt Controller.
  */
 void hv_synic_enable_regs(unsigned int cpu)
 {
-- 
2.43.0

[PATCH hyperv-next v6 10/17] Drivers: hv: Check message and event pages for non-NULL before iounmap()

[Roman Kisel]

It might happen that some hyp SynIC pages aren't allocated.

Check for that and only then call iounmap().

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/hv.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 95631c08a71f..8e102bcc0be8 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -369,8 +369,10 @@ void hv_synic_disable_regs(unsigned int cpu)
 	 */
 	simp.simp_enabled = 0;
 	if (ms_hyperv.paravisor_present || hv_root_partition()) {
-		iounmap(hv_cpu->hyp_synic_message_page);
-		hv_cpu->hyp_synic_message_page = NULL;
+		if (hv_cpu->hyp_synic_message_page) {
+			iounmap(hv_cpu->hyp_synic_message_page);
+			hv_cpu->hyp_synic_message_page = NULL;
+		}
 	} else {
 		simp.base_simp_gpa = 0;
 	}
@@ -381,8 +383,10 @@ void hv_synic_disable_regs(unsigned int cpu)
 	siefp.siefp_enabled = 0;
 
 	if (ms_hyperv.paravisor_present || hv_root_partition()) {
-		iounmap(hv_cpu->hyp_synic_event_page);
-		hv_cpu->hyp_synic_event_page = NULL;
+		if (hv_cpu->hyp_synic_event_page) {
+			iounmap(hv_cpu->hyp_synic_event_page);
+			hv_cpu->hyp_synic_event_page = NULL;
+		}
 	} else {
 		siefp.base_siefp_gpa = 0;
 	}
-- 
2.43.0

[PATCH hyperv-next v6 11/17] Drivers: hv: Rename the SynIC enable and disable routines

[Roman Kisel]

The confidential VMBus requires support for the both hypervisor
facing SynIC and the paravisor one.

Rename the functions that enable and disable SynIC with the
hypervisor. No functional changes.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/channel_mgmt.c |  2 +-
 drivers/hv/hv.c           | 11 ++++++-----
 drivers/hv/hyperv_vmbus.h |  4 ++--
 drivers/hv/vmbus_drv.c    |  6 +++---
 4 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 1a33c6944b3c..6d66cbc9030b 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -846,7 +846,7 @@ static void vmbus_wait_for_unload(void)
 			/*
 			 * In a CoCo VM the hyp_synic_message_page is not allocated
 			 * in hv_synic_alloc(). Instead it is set/cleared in
-			 * hv_synic_enable_regs() and hv_synic_disable_regs()
+			 * hv_hyp_synic_enable_regs() and hv_hyp_synic_disable_regs()
 			 * such that it is set only when the CPU is online. If
 			 * not all present CPUs are online, the message page
 			 * might be NULL, so skip such CPUs.
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 8e102bcc0be8..76138ebe7c0c 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -268,9 +268,10 @@ void hv_synic_free(void)
 }
 
 /*
- * hv_synic_enable_regs - Initialize the Synthetic Interrupt Controller.
+ * hv_hyp_synic_enable_regs - Initialize the Synthetic Interrupt Controller
+ * with the hypervisor.
  */
-void hv_synic_enable_regs(unsigned int cpu)
+void hv_hyp_synic_enable_regs(unsigned int cpu)
 {
 	struct hv_per_cpu_context *hv_cpu =
 		per_cpu_ptr(hv_context.cpu_context, cpu);
@@ -336,14 +337,14 @@ void hv_synic_enable_regs(unsigned int cpu)
 
 int hv_synic_init(unsigned int cpu)
 {
-	hv_synic_enable_regs(cpu);
+	hv_hyp_synic_enable_regs(cpu);
 
 	hv_stimer_legacy_init(cpu, VMBUS_MESSAGE_SINT);
 
 	return 0;
 }
 
-void hv_synic_disable_regs(unsigned int cpu)
+void hv_hyp_synic_disable_regs(unsigned int cpu)
 {
 	struct hv_per_cpu_context *hv_cpu =
 		per_cpu_ptr(hv_context.cpu_context, cpu);
@@ -530,7 +531,7 @@ int hv_synic_cleanup(unsigned int cpu)
 always_cleanup:
 	hv_stimer_legacy_cleanup(cpu);
 
-	hv_synic_disable_regs(cpu);
+	hv_hyp_synic_disable_regs(cpu);
 
 	return ret;
 }
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 3c70051c0431..552ed782bcfc 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -190,10 +190,10 @@ extern int hv_synic_alloc(void);
 
 extern void hv_synic_free(void);
 
-extern void hv_synic_enable_regs(unsigned int cpu);
+extern void hv_hyp_synic_enable_regs(unsigned int cpu);
 extern int hv_synic_init(unsigned int cpu);
 
-extern void hv_synic_disable_regs(unsigned int cpu);
+extern void hv_hyp_synic_disable_regs(unsigned int cpu);
 extern int hv_synic_cleanup(unsigned int cpu);
 
 /* Interface */
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index e12f0ba0701f..2b5bf672c467 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -2810,7 +2810,7 @@ static void hv_crash_handler(struct pt_regs *regs)
 	 */
 	cpu = smp_processor_id();
 	hv_stimer_cleanup(cpu);
-	hv_synic_disable_regs(cpu);
+	hv_hyp_synic_disable_regs(cpu);
 };
 
 static int hv_synic_suspend(void)
@@ -2835,14 +2835,14 @@ static int hv_synic_suspend(void)
 	 * interrupts-disabled context.
 	 */
 
-	hv_synic_disable_regs(0);
+	hv_hyp_synic_disable_regs(0);
 
 	return 0;
 }
 
 static void hv_synic_resume(void)
 {
-	hv_synic_enable_regs(0);
+	hv_hyp_synic_enable_regs(0);
 
 	/*
 	 * Note: we don't need to call hv_stimer_init(0), because the timer
-- 
2.43.0

[PATCH hyperv-next v6 12/17] Drivers: hv: Functions for setting up and tearing down the paravisor SynIC

[Roman Kisel]

The confidential VMBus runs with the paravisor SynIC and requires
configuring it with the paravisor.

Add the functions for configuring the paravisor SynIC. Update
overall SynIC initialization logic to initialize the SynIC if it
is present. Finally, break out SynIC interrupt enable/disable
code into separate functions so that SynIC interrupts can be
enabled or disabled via the paravisor instead of the hypervisor
if the paravisor SynIC is present.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/hv.c | 138 +++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 126 insertions(+), 12 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 76138ebe7c0c..5789b41be76c 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -278,9 +278,8 @@ void hv_hyp_synic_enable_regs(unsigned int cpu)
 	union hv_synic_simp simp;
 	union hv_synic_siefp siefp;
 	union hv_synic_sint shared_sint;
-	union hv_synic_scontrol sctrl;
 
-	/* Setup the Synic's message page */
+	/* Setup the Synic's message page with the hypervisor. */
 	simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
 	simp.simp_enabled = 1;
 
@@ -299,7 +298,7 @@ void hv_hyp_synic_enable_regs(unsigned int cpu)
 
 	hv_set_msr(HV_MSR_SIMP, simp.as_uint64);
 
-	/* Setup the Synic's event page */
+	/* Setup the Synic's event page with the hypervisor. */
 	siefp.as_uint64 = hv_get_msr(HV_MSR_SIEFP);
 	siefp.siefp_enabled = 1;
 
@@ -327,6 +326,11 @@ void hv_hyp_synic_enable_regs(unsigned int cpu)
 	shared_sint.masked = false;
 	shared_sint.auto_eoi = hv_recommend_using_aeoi();
 	hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
+}
+
+static void hv_hyp_synic_enable_interrupts(void)
+{
+	union hv_synic_scontrol sctrl;
 
 	/* Enable the global synic bit */
 	sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
@@ -335,9 +339,59 @@ void hv_hyp_synic_enable_regs(unsigned int cpu)
 	hv_set_msr(HV_MSR_SCONTROL, sctrl.as_uint64);
 }
 
+static void hv_para_synic_enable_regs(unsigned int cpu)
+{
+	union hv_synic_simp simp;
+	union hv_synic_siefp siefp;
+	struct hv_per_cpu_context *hv_cpu
+		= per_cpu_ptr(hv_context.cpu_context, cpu);
+
+	/* Setup the Synic's message page with the paravisor. */
+	simp.as_uint64 = hv_para_get_synic_register(HV_MSR_SIMP);
+	simp.simp_enabled = 1;
+	simp.base_simp_gpa = virt_to_phys(hv_cpu->para_synic_message_page)
+			>> HV_HYP_PAGE_SHIFT;
+	hv_para_set_synic_register(HV_MSR_SIMP, simp.as_uint64);
+
+	/* Setup the Synic's event page with the paravisor. */
+	siefp.as_uint64 = hv_para_get_synic_register(HV_MSR_SIEFP);
+	siefp.siefp_enabled = 1;
+	siefp.base_siefp_gpa = virt_to_phys(hv_cpu->para_synic_event_page)
+			>> HV_HYP_PAGE_SHIFT;
+	hv_para_set_synic_register(HV_MSR_SIEFP, siefp.as_uint64);
+}
+
+static void hv_para_synic_enable_interrupts(void)
+{
+	union hv_synic_scontrol sctrl;
+
+	/* Enable the global synic bit */
+	sctrl.as_uint64 = hv_para_get_synic_register(HV_MSR_SCONTROL);
+	sctrl.enable = 1;
+	hv_para_set_synic_register(HV_MSR_SCONTROL, sctrl.as_uint64);
+}
+
 int hv_synic_init(unsigned int cpu)
 {
+	if (vmbus_is_confidential())
+		hv_para_synic_enable_regs(cpu);
+
+	/*
+	 * The SINT is set in hv_hyp_synic_enable_regs() by calling
+	 * hv_set_msr(). hv_set_msr() in turn has special case code for the
+	 * SINT MSRs that write to the hypervisor version of the MSR *and*
+	 * the paravisor version of the MSR (but *without* the proxy bit when
+	 * VMBus is confidential).
+	 *
+	 * Then enable interrupts via the paravisor if VMBus is confidential,
+	 * and otherwise via the hypervisor.
+	 */
+
 	hv_hyp_synic_enable_regs(cpu);
+	if (vmbus_is_confidential())
+		hv_para_synic_enable_interrupts();
+	else
+		hv_hyp_synic_enable_interrupts();
 
 	hv_stimer_legacy_init(cpu, VMBUS_MESSAGE_SINT);
 
@@ -351,7 +405,6 @@ void hv_hyp_synic_disable_regs(unsigned int cpu)
 	union hv_synic_sint shared_sint;
 	union hv_synic_simp simp;
 	union hv_synic_siefp siefp;
-	union hv_synic_scontrol sctrl;
 
 	shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
 
@@ -363,7 +416,7 @@ void hv_hyp_synic_disable_regs(unsigned int cpu)
 
 	simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
 	/*
-	 * In Isolation VM, sim and sief pages are allocated by
+	 * In Isolation VM, simp and sief pages are allocated by
 	 * paravisor. These pages also will be used by kdump
 	 * kernel. So just reset enable bit here and keep page
 	 * addresses.
@@ -393,14 +446,42 @@ void hv_hyp_synic_disable_regs(unsigned int cpu)
 	}
 
 	hv_set_msr(HV_MSR_SIEFP, siefp.as_uint64);
+}
+
+static void hv_hyp_synic_disable_interrupts(void)
+{
+	union hv_synic_scontrol sctrl;
 
 	/* Disable the global synic bit */
 	sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
 	sctrl.enable = 0;
 	hv_set_msr(HV_MSR_SCONTROL, sctrl.as_uint64);
+}
 
-	if (vmbus_irq != -1)
-		disable_percpu_irq(vmbus_irq);
+static void hv_para_synic_disable_regs(unsigned int cpu)
+{
+	union hv_synic_simp simp;
+	union hv_synic_siefp siefp;
+
+	/* Disable SynIC's message page in the paravisor. */
+	simp.as_uint64 = hv_para_get_synic_register(HV_MSR_SIMP);
+	simp.simp_enabled = 0;
+	hv_para_set_synic_register(HV_MSR_SIMP, simp.as_uint64);
+
+	/* Disable SynIC's event page in the paravisor. */
+	siefp.as_uint64 = hv_para_get_synic_register(HV_MSR_SIEFP);
+	siefp.siefp_enabled = 0;
+	hv_para_set_synic_register(HV_MSR_SIEFP, siefp.as_uint64);
+}
+
+static void hv_para_synic_disable_interrupts(void)
+{
+	union hv_synic_scontrol sctrl;
+
+	/* Disable the global synic bit */
+	sctrl.as_uint64 = hv_para_get_synic_register(HV_MSR_SCONTROL);
+	sctrl.enable = 0;
+	hv_para_set_synic_register(HV_MSR_SCONTROL, sctrl.as_uint64);
 }
 
 #define HV_MAX_TRIES 3
@@ -413,16 +494,18 @@ void hv_hyp_synic_disable_regs(unsigned int cpu)
  * that the normal interrupt handling mechanism will find and process the channel interrupt
  * "very soon", and in the process clear the bit.
  */
-static bool hv_synic_event_pending(void)
+static bool __hv_synic_event_pending(union hv_synic_event_flags *event, int sint)
 {
-	struct hv_per_cpu_context *hv_cpu = this_cpu_ptr(hv_context.cpu_context);
-	union hv_synic_event_flags *event =
-		(union hv_synic_event_flags *)hv_cpu->hyp_synic_event_page + VMBUS_MESSAGE_SINT;
-	unsigned long *recv_int_page = event->flags; /* assumes VMBus version >= VERSION_WIN8 */
+	unsigned long *recv_int_page;
 	bool pending;
 	u32 relid;
 	int tries = 0;
 
+	if (!event)
+		return false;
+
+	event += sint;
+	recv_int_page = event->flags; /* assumes VMBus version >= VERSION_WIN8 */
 retry:
 	pending = false;
 	for_each_set_bit(relid, recv_int_page, HV_EVENT_FLAGS_COUNT) {
@@ -439,6 +522,17 @@ static bool hv_synic_event_pending(void)
 	return pending;
 }
 
+static bool hv_synic_event_pending(void)
+{
+	struct hv_per_cpu_context *hv_cpu = this_cpu_ptr(hv_context.cpu_context);
+	union hv_synic_event_flags *hyp_synic_event_page = hv_cpu->hyp_synic_event_page;
+	union hv_synic_event_flags *para_synic_event_page = hv_cpu->para_synic_event_page;
+
+	return
+		__hv_synic_event_pending(hyp_synic_event_page, VMBUS_MESSAGE_SINT) ||
+		__hv_synic_event_pending(para_synic_event_page, VMBUS_MESSAGE_SINT);
+}
+
 static int hv_pick_new_cpu(struct vmbus_channel *channel)
 {
 	int ret = -EBUSY;
@@ -531,7 +625,27 @@ int hv_synic_cleanup(unsigned int cpu)
 always_cleanup:
 	hv_stimer_legacy_cleanup(cpu);
 
+	/*
+	 * First, disable the event and message pages
+	 * used for communicating with the host, and then
+	 * disable the host interrupts if VMBus is not
+	 * confidential.
+	 */
 	hv_hyp_synic_disable_regs(cpu);
+	if (!vmbus_is_confidential())
+		hv_hyp_synic_disable_interrupts();
+
+	/*
+	 * Perform the same steps for the Confidential VMBus.
+	 * The sequencing provides the guarantee that no data
+	 * may be posted for processing before disabling interrupts.
+	 */
+	if (vmbus_is_confidential()) {
+		hv_para_synic_disable_regs(cpu);
+		hv_para_synic_disable_interrupts();
+	}
+	if (vmbus_irq != -1)
+		disable_percpu_irq(vmbus_irq);
 
 	return ret;
 }
-- 
2.43.0

[PATCH hyperv-next v6 13/17] Drivers: hv: Allocate encrypted buffers when requested

[Roman Kisel]

Confidential VMBus is built around using buffers not shared with
the host.

Support allocating encrypted buffers when requested.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/channel.c      | 49 +++++++++++++++++++++++----------------
 drivers/hv/hyperv_vmbus.h |  3 ++-
 drivers/hv/ring_buffer.c  |  5 ++--
 3 files changed, 34 insertions(+), 23 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 162d6aeece7b..d69713201bef 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -444,20 +444,23 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
 		return ret;
 	}
 
-	/*
-	 * Set the "decrypted" flag to true for the set_memory_decrypted()
-	 * success case. In the failure case, the encryption state of the
-	 * memory is unknown. Leave "decrypted" as true to ensure the
-	 * memory will be leaked instead of going back on the free list.
-	 */
-	gpadl->decrypted = true;
-	ret = set_memory_decrypted((unsigned long)kbuffer,
-				   PFN_UP(size));
-	if (ret) {
-		dev_warn(&channel->device_obj->device,
-			 "Failed to set host visibility for new GPADL %d.\n",
-			 ret);
-		return ret;
+	gpadl->decrypted = !((channel->co_external_memory && type == HV_GPADL_BUFFER) ||
+		(channel->co_ring_buffer && type == HV_GPADL_RING));
+	if (gpadl->decrypted) {
+		/*
+		 * The "decrypted" flag being true assumes that set_memory_decrypted() succeeds.
+		 * But if it fails, the encryption state of the memory is unknown. In that case,
+		 * leave "decrypted" as true to ensure the memory is leaked instead of going back
+		 * on the free list.
+		 */
+		ret = set_memory_decrypted((unsigned long)kbuffer,
+					PFN_UP(size));
+		if (ret) {
+			dev_warn(&channel->device_obj->device,
+				"Failed to set host visibility for new GPADL %d.\n",
+				ret);
+			return ret;
+		}
 	}
 
 	init_completion(&msginfo->waitevent);
@@ -545,8 +548,10 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
 		 * left as true so the memory is leaked instead of being
 		 * put back on the free list.
 		 */
-		if (!set_memory_encrypted((unsigned long)kbuffer, PFN_UP(size)))
-			gpadl->decrypted = false;
+		if (gpadl->decrypted) {
+			if (!set_memory_encrypted((unsigned long)kbuffer, PFN_UP(size)))
+				gpadl->decrypted = false;
+		}
 	}
 
 	return ret;
@@ -677,12 +682,13 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
 		goto error_clean_ring;
 
 	err = hv_ringbuffer_init(&newchannel->outbound,
-				 page, send_pages, 0);
+				 page, send_pages, 0, newchannel->co_ring_buffer);
 	if (err)
 		goto error_free_gpadl;
 
 	err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
-				 recv_pages, newchannel->max_pkt_size);
+				 recv_pages, newchannel->max_pkt_size,
+				 newchannel->co_ring_buffer);
 	if (err)
 		goto error_free_gpadl;
 
@@ -863,8 +869,11 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, struct vmbus_gpadl *gpad
 
 	kfree(info);
 
-	ret = set_memory_encrypted((unsigned long)gpadl->buffer,
-				   PFN_UP(gpadl->size));
+	if (gpadl->decrypted)
+		ret = set_memory_encrypted((unsigned long)gpadl->buffer,
+					PFN_UP(gpadl->size));
+	else
+		ret = 0;
 	if (ret)
 		pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret);
 
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 552ed782bcfc..f7fc2630c054 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -201,7 +201,8 @@ extern int hv_synic_cleanup(unsigned int cpu);
 void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
 
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
-		       struct page *pages, u32 pagecnt, u32 max_pkt_size);
+		       struct page *pages, u32 pagecnt, u32 max_pkt_size,
+			   bool confidential);
 
 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);
 
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 23ce1fb70de1..3c421a7f78c0 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -184,7 +184,8 @@ void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
 
 /* Initialize the ring buffer. */
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
-		       struct page *pages, u32 page_cnt, u32 max_pkt_size)
+		       struct page *pages, u32 page_cnt, u32 max_pkt_size,
+			   bool confidential)
 {
 	struct page **pages_wraparound;
 	int i;
@@ -208,7 +209,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 
 	ring_info->ring_buffer = (struct hv_ring_buffer *)
 		vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
-			pgprot_decrypted(PAGE_KERNEL));
+			confidential ? PAGE_KERNEL : pgprot_decrypted(PAGE_KERNEL));
 
 	kfree(pages_wraparound);
 	if (!ring_info->ring_buffer)
-- 
2.43.0

[PATCH hyperv-next v6 14/17] Drivers: hv: Free msginfo when the buffer fails to decrypt

[Roman Kisel]

The early failure path in __vmbus_establish_gpadl() doesn't deallocate
msginfo if the buffer fails to decrypt.

Fix the leak by breaking out the cleanup code into a separate function
and calling it where required.

Fixes: d4dccf353db80 ("Drivers: hv: vmbus: Mark vmbus ring buffer visible to host in Isolation VM")
Reported-by: Michael Kelley <mkhlinux@outlook.com>
Closes: https://lore.kernel.org/linux-hyperv/SN6PR02MB41573796F9787F67E0E97049D472A@SN6PR02MB4157.namprd02.prod.outlook.com
Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/channel.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index d69713201bef..88485d255a42 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -410,6 +410,21 @@ static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
 	return 0;
 }
 
+static void vmbus_free_channel_msginfo(struct vmbus_channel_msginfo *msginfo)
+{
+	struct vmbus_channel_msginfo *submsginfo, *tmp;
+
+	if (!msginfo)
+		return;
+
+	list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
+				 msglistentry) {
+		kfree(submsginfo);
+	}
+
+	kfree(msginfo);
+}
+
 /*
  * __vmbus_establish_gpadl - Establish a GPADL for a buffer or ringbuffer
  *
@@ -429,7 +444,7 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
 	struct vmbus_channel_gpadl_header *gpadlmsg;
 	struct vmbus_channel_gpadl_body *gpadl_body;
 	struct vmbus_channel_msginfo *msginfo = NULL;
-	struct vmbus_channel_msginfo *submsginfo, *tmp;
+	struct vmbus_channel_msginfo *submsginfo;
 	struct list_head *curr;
 	u32 next_gpadl_handle;
 	unsigned long flags;
@@ -459,6 +474,7 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
 			dev_warn(&channel->device_obj->device,
 				"Failed to set host visibility for new GPADL %d.\n",
 				ret);
+			vmbus_free_channel_msginfo(msginfo);
 			return ret;
 		}
 	}
@@ -535,12 +551,8 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
 	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 	list_del(&msginfo->msglistentry);
 	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
-	list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
-				 msglistentry) {
-		kfree(submsginfo);
-	}
 
-	kfree(msginfo);
+	vmbus_free_channel_msginfo(msginfo);
 
 	if (ret) {
 		/*
-- 
2.43.0

[PATCH hyperv-next v6 15/17] Drivers: hv: Support confidential VMBus channels

[Roman Kisel]

To make use of Confidential VMBus channels, initialize the
co_ring_buffers and co_external_memory fields of the channel
structure.

Advertise support upon negotiating the version and compute
values for those fields and initialize them.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/channel_mgmt.c | 19 +++++++++++++++++++
 drivers/hv/connection.c   |  3 +++
 2 files changed, 22 insertions(+)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 6d66cbc9030b..74fed2c073d4 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -1022,6 +1022,7 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 	struct vmbus_channel_offer_channel *offer;
 	struct vmbus_channel *oldchannel, *newchannel;
 	size_t offer_sz;
+	bool co_ring_buffer, co_external_memory;
 
 	offer = (struct vmbus_channel_offer_channel *)hdr;
 
@@ -1034,6 +1035,22 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 		return;
 	}
 
+	co_ring_buffer = is_co_ring_buffer(offer);
+	co_external_memory = is_co_external_memory(offer);
+	if (!co_ring_buffer && co_external_memory) {
+		pr_err("Invalid offer relid=%d: the ring buffer isn't encrypted\n",
+			offer->child_relid);
+		return;
+	}
+	if (co_ring_buffer || co_external_memory) {
+		if (vmbus_proto_version < VERSION_WIN10_V6_0 || !vmbus_is_confidential()) {
+			pr_err("Invalid offer relid=%d: no support for confidential VMBus\n",
+				offer->child_relid);
+			atomic_dec(&vmbus_connection.offer_in_progress);
+			return;
+		}
+	}
+
 	oldchannel = find_primary_channel_by_offer(offer);
 
 	if (oldchannel != NULL) {
@@ -1112,6 +1129,8 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 		pr_err("Unable to allocate channel object\n");
 		return;
 	}
+	newchannel->co_ring_buffer = co_ring_buffer;
+	newchannel->co_external_memory = co_external_memory;
 
 	vmbus_setup_channel_state(newchannel, offer);
 
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 1fe3573ae52a..5ac9232396f7 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -105,6 +105,9 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
 		vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID;
 	}
 
+	if (vmbus_is_confidential() && version >= VERSION_WIN10_V6_0)
+		msg->feature_flags = VMBUS_FEATURE_FLAG_CONFIDENTIAL_CHANNELS;
+
 	/*
 	 * shared_gpa_boundary is zero in non-SNP VMs, so it's safe to always
 	 * bitwise OR it
-- 
2.43.0

[PATCH hyperv-next v6 16/17] Drivers: hv: Set the default VMBus version to 6.0

[Roman Kisel]

The confidential VMBus is supported by the protocol version
6.0 onwards.

Attempt to establish the VMBus 6.0 connection thus enabling
the confidential VMBus features when available.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/connection.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 5ac9232396f7..5d9cb5bf2d62 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -51,6 +51,7 @@ EXPORT_SYMBOL_GPL(vmbus_proto_version);
  * Linux guests and are not listed.
  */
 static __u32 vmbus_versions[] = {
+	VERSION_WIN10_V6_0,
 	VERSION_WIN10_V5_3,
 	VERSION_WIN10_V5_2,
 	VERSION_WIN10_V5_1,
@@ -65,7 +66,7 @@ static __u32 vmbus_versions[] = {
  * Maximal VMBus protocol version guests can negotiate.  Useful to cap the
  * VMBus version for testing and debugging purpose.
  */
-static uint max_version = VERSION_WIN10_V5_3;
+static uint max_version = VERSION_WIN10_V6_0;
 
 module_param(max_version, uint, S_IRUGO);
 MODULE_PARM_DESC(max_version,
-- 
2.43.0

[PATCH hyperv-next v6 17/17] Drivers: hv: Support establishing the confidential VMBus connection

[Roman Kisel]

To establish the confidential VMBus connection the CoCo VM, the guest
first checks on the confidential VMBus availability, and then proceeds
to initializing the communication stack.

Implement that in the VMBus driver initialization.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/vmbus_drv.c | 168 ++++++++++++++++++++++++++---------------
 1 file changed, 106 insertions(+), 62 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 2b5bf672c467..0dc4692b411a 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1057,12 +1057,9 @@ static void vmbus_onmessage_work(struct work_struct *work)
 	kfree(ctx);
 }
 
-void vmbus_on_msg_dpc(unsigned long data)
+static void __vmbus_on_msg_dpc(void *message_page_addr)
 {
-	struct hv_per_cpu_context *hv_cpu = (void *)data;
-	void *page_addr = hv_cpu->hyp_synic_message_page;
-	struct hv_message msg_copy, *msg = (struct hv_message *)page_addr +
-				  VMBUS_MESSAGE_SINT;
+	struct hv_message msg_copy, *msg;
 	struct vmbus_channel_message_header *hdr;
 	enum vmbus_channel_message_type msgtype;
 	const struct vmbus_channel_message_table_entry *entry;
@@ -1070,6 +1067,10 @@ void vmbus_on_msg_dpc(unsigned long data)
 	__u8 payload_size;
 	u32 message_type;
 
+	if (!message_page_addr)
+		return;
+	msg = (struct hv_message *)message_page_addr + VMBUS_MESSAGE_SINT;
+
 	/*
 	 * 'enum vmbus_channel_message_type' is supposed to always be 'u32' as
 	 * it is being used in 'struct vmbus_channel_message_header' definition
@@ -1195,6 +1196,14 @@ void vmbus_on_msg_dpc(unsigned long data)
 	vmbus_signal_eom(msg, message_type);
 }
 
+void vmbus_on_msg_dpc(unsigned long data)
+{
+	struct hv_per_cpu_context *hv_cpu = (void *)data;
+
+	__vmbus_on_msg_dpc(hv_cpu->hyp_synic_message_page);
+	__vmbus_on_msg_dpc(hv_cpu->para_synic_message_page);
+}
+
 #ifdef CONFIG_PM_SLEEP
 /*
  * Fake RESCIND_CHANNEL messages to clean up hv_sock channels by force for
@@ -1233,21 +1242,19 @@ static void vmbus_force_channel_rescinded(struct vmbus_channel *channel)
 #endif /* CONFIG_PM_SLEEP */
 
 /*
- * Schedule all channels with events pending
+ * Schedule all channels with events pending.
+ * The event page can be directly checked to get the id of
+ * the channel that has the interrupt pending.
  */
-static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
+static void vmbus_chan_sched(void *event_page_addr)
 {
 	unsigned long *recv_int_page;
 	u32 maxbits, relid;
+	union hv_synic_event_flags *event;
 
-	/*
-	 * The event page can be directly checked to get the id of
-	 * the channel that has the interrupt pending.
-	 */
-	void *page_addr = hv_cpu->hyp_synic_event_page;
-	union hv_synic_event_flags *event
-		= (union hv_synic_event_flags *)page_addr +
-					 VMBUS_MESSAGE_SINT;
+	if (!event_page_addr)
+		return;
+	event = (union hv_synic_event_flags *)event_page_addr + VMBUS_MESSAGE_SINT;
 
 	maxbits = HV_EVENT_FLAGS_COUNT;
 	recv_int_page = event->flags;
@@ -1255,6 +1262,11 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
 	if (unlikely(!recv_int_page))
 		return;
 
+	/*
+	 * Suggested-by: Michael Kelley <mhklinux@outlook.com>
+	 * One possible optimization would be to keep track of the largest relID that's in use,
+	 * and only scan up to that relID.
+	 */
 	for_each_set_bit(relid, recv_int_page, maxbits) {
 		void (*callback_fn)(void *context);
 		struct vmbus_channel *channel;
@@ -1318,26 +1330,35 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
 	}
 }
 
-static void vmbus_isr(void)
+static void vmbus_message_sched(struct hv_per_cpu_context *hv_cpu, void *message_page_addr)
 {
-	struct hv_per_cpu_context *hv_cpu
-		= this_cpu_ptr(hv_context.cpu_context);
-	void *page_addr;
 	struct hv_message *msg;
 
-	vmbus_chan_sched(hv_cpu);
-
-	page_addr = hv_cpu->hyp_synic_message_page;
-	msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
+	if (!message_page_addr)
+		return;
+	msg = (struct hv_message *)message_page_addr + VMBUS_MESSAGE_SINT;
 
 	/* Check if there are actual msgs to be processed */
 	if (msg->header.message_type != HVMSG_NONE) {
 		if (msg->header.message_type == HVMSG_TIMER_EXPIRED) {
 			hv_stimer0_isr();
 			vmbus_signal_eom(msg, HVMSG_TIMER_EXPIRED);
-		} else
+		} else {
 			tasklet_schedule(&hv_cpu->msg_dpc);
+		}
 	}
+}
+
+static void vmbus_isr(void)
+{
+	struct hv_per_cpu_context *hv_cpu
+		= this_cpu_ptr(hv_context.cpu_context);
+
+	vmbus_chan_sched(hv_cpu->hyp_synic_event_page);
+	vmbus_chan_sched(hv_cpu->para_synic_event_page);
+
+	vmbus_message_sched(hv_cpu, hv_cpu->hyp_synic_message_page);
+	vmbus_message_sched(hv_cpu, hv_cpu->para_synic_message_page);
 
 	add_interrupt_randomness(vmbus_interrupt);
 }
@@ -1355,6 +1376,59 @@ static void vmbus_percpu_work(struct work_struct *work)
 	hv_synic_init(cpu);
 }
 
+static int vmbus_alloc_synic_and_connect(void)
+{
+	int ret, cpu;
+	struct work_struct __percpu *works;
+	int hyperv_cpuhp_online;
+
+	ret = hv_synic_alloc();
+	if (ret < 0)
+		goto err_alloc;
+
+	works = alloc_percpu(struct work_struct);
+	if (!works) {
+		ret = -ENOMEM;
+		goto err_alloc;
+	}
+
+	/*
+	 * Initialize the per-cpu interrupt state and stimer state.
+	 * Then connect to the host.
+	 */
+	cpus_read_lock();
+	for_each_online_cpu(cpu) {
+		struct work_struct *work = per_cpu_ptr(works, cpu);
+
+		INIT_WORK(work, vmbus_percpu_work);
+		schedule_work_on(cpu, work);
+	}
+
+	for_each_online_cpu(cpu)
+		flush_work(per_cpu_ptr(works, cpu));
+
+	/* Register the callbacks for possible CPU online/offline'ing */
+	ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",
+						   hv_synic_init, hv_synic_cleanup);
+	cpus_read_unlock();
+	free_percpu(works);
+	if (ret < 0)
+		goto err_alloc;
+	hyperv_cpuhp_online = ret;
+
+	ret = vmbus_connect();
+	if (ret)
+		goto err_connect;
+	return 0;
+
+err_connect:
+	cpuhp_remove_state(hyperv_cpuhp_online);
+	return -ENODEV;
+err_alloc:
+	hv_synic_free();
+	return -ENOMEM;
+}
+
 /*
  * vmbus_bus_init -Main vmbus driver initialization routine.
  *
@@ -1365,8 +1439,7 @@ static void vmbus_percpu_work(struct work_struct *work)
  */
 static int vmbus_bus_init(void)
 {
-	int ret, cpu;
-	struct work_struct __percpu *works;
+	int ret;
 
 	ret = hv_init();
 	if (ret != 0) {
@@ -1401,41 +1474,15 @@ static int vmbus_bus_init(void)
 		}
 	}
 
-	ret = hv_synic_alloc();
-	if (ret)
-		goto err_alloc;
-
-	works = alloc_percpu(struct work_struct);
-	if (!works) {
-		ret = -ENOMEM;
-		goto err_alloc;
-	}
-
 	/*
-	 * Initialize the per-cpu interrupt state and stimer state.
-	 * Then connect to the host.
+	 * Cache the value as getting it involves a VM exit on x86(_64), and
+	 * doing that on each VP while initializing SynIC's wastes time.
 	 */
-	cpus_read_lock();
-	for_each_online_cpu(cpu) {
-		struct work_struct *work = per_cpu_ptr(works, cpu);
-
-		INIT_WORK(work, vmbus_percpu_work);
-		schedule_work_on(cpu, work);
-	}
-
-	for_each_online_cpu(cpu)
-		flush_work(per_cpu_ptr(works, cpu));
-
-	/* Register the callbacks for possible CPU online/offline'ing */
-	ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",
-						   hv_synic_init, hv_synic_cleanup);
-	cpus_read_unlock();
-	free_percpu(works);
-	if (ret < 0)
-		goto err_alloc;
-	hyperv_cpuhp_online = ret;
-
-	ret = vmbus_connect();
+	is_confidential = ms_hyperv.confidential_vmbus_available;
+	if (is_confidential)
+		pr_info("Establishing connection to the confidential VMBus\n");
+	hv_para_set_sint_proxy(!is_confidential);
+	ret = vmbus_alloc_synic_and_connect();
 	if (ret)
 		goto err_connect;
 
@@ -1451,9 +1498,6 @@ static int vmbus_bus_init(void)
 	return 0;
 
 err_connect:
-	cpuhp_remove_state(hyperv_cpuhp_online);
-err_alloc:
-	hv_synic_free();
 	if (vmbus_irq == -1) {
 		hv_remove_vmbus_handler();
 	} else {
-- 
2.43.0

Re: [PATCH hyperv-next v6 05/17] arch/x86: mshyperv: Trap on access for some synthetic MSRs

[kernel test robot]

Hi Roman,

kernel test robot noticed the following build warnings:

[auto build test WARNING on b595edcb24727e7f93e7962c3f6f971cc16dd29e]

url:    https://github.com/intel-lab-lkp/linux/commits/Roman-Kisel/Documentation-hyperv-Confidential-VMBus/20251004-063158
base:   b595edcb24727e7f93e7962c3f6f971cc16dd29e
patch link:    https://lore.kernel.org/r/20251003222710.6257-6-romank%40linux.microsoft.com
patch subject: [PATCH hyperv-next v6 05/17] arch/x86: mshyperv: Trap on access for some synthetic MSRs
config: i386-buildonly-randconfig-003-20251004 (https://download.01.org/0day-ci/archive/20251004/202510041544.zPic8ogA-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251004/202510041544.zPic8ogA-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202510041544.zPic8ogA-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/x86/kernel/cpu/mshyperv.c:46:13: warning: unused variable 'hv_para_sint_proxy' [-Wunused-variable]
      46 | static bool hv_para_sint_proxy;
         |             ^~~~~~~~~~~~~~~~~~
   1 warning generated.


vim +/hv_para_sint_proxy +46 arch/x86/kernel/cpu/mshyperv.c

    41	
    42	/*
    43	 * When running with the paravisor, controls proxying the synthetic interrupts
    44	 * from the host
    45	 */
  > 46	static bool hv_para_sint_proxy;
    47	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

RE: [PATCH hyperv-next v6 00/17] Confidential VMBus

[Michael Kelley]

From: Roman Kisel <romank@linux.microsoft.com> Sent: Friday, October 3, 2025 3:27 PM
> 
> Greetings everyone,
> 
> We've got to the 6th version of the patch series, and the full changelog
> is at the end of the cover letter. I addressed feedback from
> Michael and Wei on the previous version of the patch series.
> 
> Since v5, the fallback mechanism for establishing the VMBus connection
> is no longer used as the availability of the Confidential VMBus is
> now indicated by a bit in the Virtualization Stack (VS) CPUID leaf.
> The v6 patch series breaks that out into a separate patch seizing
> the opportunity to refactor the code that uses the same leaf.
> 
> That is obviously an x86_64 specific technique. On ARM64, the
> Confidential VMBus is expected to be required once support for ARM CCA is
> implemented. Despite that change, the functions for getting and setting
> registers via paravisor remain fallible. 

This statement seems to contradict your description of the v6
changes further down in this cover letter:

     - Gave another thought to the fallible routines for getting and setting
       SynIC registers via paravisor introduced in the patch series, and after
       Michael's feedback decided to make them infallible

Patches 4 and 12 of this series also implement "infallible".

> That provides a clearer root cause
> for failures instead of printing messages about unchecked MSR accesses.
> That might seem as not needed with the paravisors run in Azure (OpenHCL
> and the TrustedLauch aka HCL paravisor). However, if someone decides to
> implement their own or tweak the exisiting one, this will help with debugging.
> 
> TLDR; is that these patches are for the Hyper-V guests, and the patches
> allow to keep data flowing from physical devices into the guests encrypted
> at the CPU level so that neither the root/host partition nor the hypervisor
> can access the data being processed (they only "see" the encrypted/garbled
> data) unless the guest decides to share it. The changes are backward compatible
> with older systems, and their full potential is realized on hardware that
> supports memory encryption.
> 
> These features also require running a paravisor, such as
> OpenHCL (https://github.com/microsoft/openvmm) used in Azure. Another
> implementation of the functionality available in this patch set is
> available in the Hyper-V UEFI: https://github.com/microsoft/mu_msvm.
> 
> A more detailed description of the patches follows.
> 
> The guests running on Hyper-V can be confidential where the memory and the
> register content are encrypted, provided that the hardware supports that
> (currently support for AMD SEV-SNP and Intel TDX is implemented) and the guest
> is capable of using these features. The confidential guests cannot be
> introspected by the host nor the hypervisor without the guest sharing the
> memory contents upon doing which the memory is decrypted.
> 
> In the confidential guests, neither the host nor the hypervisor need to be
> trusted, and the guests processing sensitive data can take advantage of that.
> 
> Not trusting the host and the hypervisor (removing them from the Trusted
> Computing Base aka TCB) necessitates that the method of communication
> between the host and the guest be changed. Here is the data flow for a
> conventional and the confidential VMBus connections (`C` stands for the
> client or VSC, `S` for the server or VSP, the `DEVICE` is a physical one,
> might be with multiple virtual functions):
> 
> 1. Without the paravisor the devices are connected to the host, and the
> host provides the device emulation or translation to the guest:
> 
>   +---- GUEST ----+       +----- DEVICE ----+        +----- HOST -----+
>   |               |       |                 |        |                |
>   |               |       |                 |        |                |
>   |               |       |                 ==========                |
>   |               |       |                 |        |                |
>   |               |       |                 |        |                |
>   |               |       |                 |        |                |
>   +----- C -------+       +-----------------+        +------- S ------+
>          ||                                                   ||
>          ||                                                   ||
>   +------||------------------ VMBus --------------------------||------+
>   |                     Interrupts, MMIO                              |
>   +-------------------------------------------------------------------+
> 
> 2. With the paravisor, the devices are connected to the paravisor, and
> the paravisor provides the device emulation or translation to the guest.
> The guest doesn't communicate with the host directly, and the guest
> communicates with the paravisor via the VMBus. The host is not trusted
> in this model, and the paravisor is trusted:
> 
>   +---- GUEST --------------- VTL0 ------+               +-- DEVICE --+
>   |                                      |               |            |
>   | +- PARAVISOR --------- VTL2 -----+   |               |            |
>   | |     +-- VMBus Relay ------+    ====+================            |
>   | |     |   Interrupts, MMIO  |    |   |               |            |
>   | |     +-------- S ----------+    |   |               +------------+
>   | |               ||               |   |
>   | +---------+     ||               |   |
>   | |  Linux  |     ||    OpenHCL    |   |
>   | |  kernel |     ||               |   |
>   | +---- C --+-----||---------------+   |
>   |       ||        ||                   |
>   +-------++------- C -------------------+               +------------+
>           ||                                             |    HOST    |
>           ||                                             +---- S -----+
>   +-------||----------------- VMBus ---------------------------||-----+
>   |                     Interrupts, MMIO                              |
>   +-------------------------------------------------------------------+
> 
> Note that in the second case the guest doesn't need to share the memory
> with the host as it communicates only with the paravisor within their
> partition boundary. That is precisely the raison d'etre and the value
> proposition of this patch series: equip the confidential guest to use
> private (encrypted) memory and rely on the paravisor when this is
> available to be more secure.
> 
> An implementation of the VMBus relay that offers the Confidential VMBus
> channels is available in the OpenVMM project as a part of the OpenHCL
> paravisor. Please refer to
> 
>   * https://openvmm.dev/guide/, and
>   * https://github.com/microsoft/openvmm 
> 
> for more information about the OpenHCL paravisor. A VMBus client
> that can work with the Confidential VMBus is available in the
> open-source Hyper-V UEFI: https://github.com/microsoft/mu_msvm.
> 
> I'd like to thank the following people for their help with this
> patch series:
> 
> * Dexuan for help with validation and the fruitful discussions,
> * Easwar for reviewing the refactoring of the page allocating and
>   freeing in `hv.c`,
> * John and Sven for the design,
> * Mike for helping to avoid pitfalls when dealing with the GFP flags,
> * Sven for blazing the trail and implementing the design in few
>   codebases.
> 
> I made sure to validate the patch series on
> 
>     {TrustedLaunch(x86_64), OpenHCL} x
>     {SNP(x86_64), TDX(x86_64), No hardware isolation, No paravisor} x
>     {VMBus 5.0, VMBus 6.0} x
>     {arm64, x86_64}.
> 
> [V6]
>     - Rebased onto the latest hyperv-next tree.
> 
>     - Gave another thought to the fallible routines for getting and setting
>       SynIC registers via paravisor introduced in the patch series, and after
>       Michael's feedback decided to make them infallible as now we have the
>       CPUID bit to indicate the availability of the Confidential VMBus. That
>       simplifies the code and makes it clearer and more robust - a reflection
>       of the improvements in the design throught the patch series iterations.
>     - Removed the sentence discussing the fallback mechanism in the Documentation
>       as it is no longer relevant.
>       **Thank you, Michael!**
> 
>     - Avoided using the macro'es for (un)masking the proxy bit thanks to
>       `union hv_synic_sint`.
>       **Thank you, Wei!**
> 
> [V5] https://lore.kernel.org/linux-hyperv/20250828010557.123869-1-romank@linux.microsoft.com/ 
>     - Rebased onto the latest hyperv-next tree.
> 
>     - Fixed build issues with the configs provided by the kernel robot.
>       **Thank you, kernel robot!**
> 
>     - Fixed the potential NULL deref in a failure path.
>       **Thank you, Michael!**
> 
>     - Removed the added blurb from the vmbus_drv.c with taxonomy of Hyper-V VMs
>       that was providing reasons for the trade-offs in the fallback code. That
>       code is no longer needed.
> 
> [V4] https://lore.kernel.org/linux-hyperv/20250714221545.5615-1-romank@linux.microsoft.com/ 
>     - Rebased the patch series on top of the latest hyperv-next branch,
>       applying changes as needed.
> 
>     - Fixed typos and clarifications all around the patch series.
>     - Added clarifications in the patch 7 for `ms_hyperv.paravisor_present && !vmbus_is_confidential()`
>       and using hypercalls vs SNP or TDX specific protocols.
>       **Thank you, Alok!**
> 
>     - Trim the Documentation changes to 80 columns.
>       **Thank you, Randy!**
> 
>     - Make sure adhere to the RST format, actually built the PDF docs
>       and made sure the layout was correct.
>     **Thank you, Jon!**
> 
>     - Better section order in Documentation.
>     - Fixed the commit descriptions where suggested.
>     - Moved EOI/EOM signaling for the confidential VMBus to the specialized function.
>     - Removed the unused `cpu` parameters.
>     - Clarified comments in the `hv_per_cpu_context` struct
>     - Explicitly test for NULL and only call `iounmap()` if non-NULL instead of
>       using `munmap()`.
>     - Don't deallocate SynIC pages in the CPU online and offline paths.
>     - Made sure the post page needs to be allocated for the future.
>     - Added comments to describe trade-offs.
>     **Thank you, Michael!**
> 
> [V3] https://lore.kernel.org/linux-hyperv/20250604004341.7194-1-romank@linux.microsoft.com/ 
>     - The patch series is rebased on top of the latest hyperv-next branch.
>     - Reworked the "wiring" diagram in the cover letter, added links to the
>       OpenVMM project and the OpenHCL paravisor.
> 
>     - More precise wording in the comments and clearer code.
>     **Thank you, Alok!**
> 
>     - Reworked the documentation patch.
>     - Split the patchset into much more granular patches.
>     - Various fixes and improvements throughout the patch series.
>     **Thank you, Michael!**
> 
> [V2] https://lore.kernel.org/linux-hyperv/20250511230758.160674-1-romank@linux.microsoft.com/ 
>     - The patch series is rebased on top of the latest hyperv-next branch.
> 
>     - Better wording in the commit messages and the Documentation.
>     **Thank you, Alok and Wei!**
> 
>     - Removed the patches 5 and 6 concerning turning bounce buffering off from
>       the previous version of the patch series as they were found to be
>       architecturally unsound. The value proposition of the patch series is not
>       diminished by this removal: these patches were an optimization and only for
>       the storage (for the simplicity sake) but not for the network. These changes
>       might be proposed in the future again after revolving the issues.
>     ** Thanks you, Christoph, Dexuan, Dan, Michael, James, Robin! **
> 
> [V1] https://lore.kernel.org/linux-hyperv/20250409000835.285105-1-romank@linux.microsoft.com/ 
> 
> Roman Kisel (17):
>   Documentation: hyperv: Confidential VMBus
>   Drivers: hv: VMBus protocol version 6.0
>   arch/x86: mshyperv: Discover Confidential VMBus availability
>   arch: hyperv: Get/set SynIC synth.registers via paravisor
>   arch/x86: mshyperv: Trap on access for some synthetic MSRs
>   Drivers: hv: Rename fields for SynIC message and event pages
>   Drivers: hv: Allocate the paravisor SynIC pages when required
>   Drivers: hv: Post messages through the confidential VMBus if available
>   Drivers: hv: remove stale comment
>   Drivers: hv: Check message and event pages for non-NULL before
>     iounmap()
>   Drivers: hv: Rename the SynIC enable and disable routines
>   Drivers: hv: Functions for setting up and tearing down the paravisor
>     SynIC
>   Drivers: hv: Allocate encrypted buffers when requested
>   Drivers: hv: Free msginfo when the buffer fails to decrypt
>   Drivers: hv: Support confidential VMBus channels
>   Drivers: hv: Set the default VMBus version to 6.0
>   Drivers: hv: Support establishing the confidential VMBus connection
> 
>  Documentation/virt/hyperv/coco.rst | 139 ++++++++++-
>  arch/x86/kernel/cpu/mshyperv.c     |  77 ++++--
>  drivers/hv/channel.c               |  73 ++++--
>  drivers/hv/channel_mgmt.c          |  27 ++-
>  drivers/hv/connection.c            |   6 +-
>  drivers/hv/hv.c                    | 372 +++++++++++++++++++----------
>  drivers/hv/hv_common.c             |  16 ++
>  drivers/hv/hyperv_vmbus.h          |  75 +++++-
>  drivers/hv/mshv_root.h             |   2 +-
>  drivers/hv/mshv_synic.c            |   6 +-
>  drivers/hv/ring_buffer.c           |   5 +-
>  drivers/hv/vmbus_drv.c             | 186 ++++++++++-----
>  include/asm-generic/mshyperv.h     |  45 +---
>  include/hyperv/hvgdk_mini.h        |   1 +
>  include/linux/hyperv.h             |  69 ++++--
>  15 files changed, 793 insertions(+), 306 deletions(-)
> 

Nice! The net lines of code added is now 487, vs. 591
lines added in v5 of this series.

Modulo the contradiction above in this cover letter, the two typos in
the documentation in Patch 1, and the simple fix for the error reported
by the kernel test robot for Patch 5, I'm happy with this entire series.
For the series,

Reviewed-by: Michael Kelley <mhklinux@outlook.com>

RE: [PATCH hyperv-next v6 01/17] Documentation: hyperv: Confidential VMBus

[Michael Kelley]

From: Roman Kisel <romank@linux.microsoft.com> Sent: Friday, October 3, 2025 3:27 PM
>
> Define what the confidential VMBus is and describe what advantages
> it offers on the capable hardware.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
> Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
>  Documentation/virt/hyperv/coco.rst | 139 ++++++++++++++++++++++++++++-
>  1 file changed, 138 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/virt/hyperv/coco.rst b/Documentation/virt/hyperv/coco.rst
> index c15d6fe34b4e..e00d94d9f88f 100644
> --- a/Documentation/virt/hyperv/coco.rst
> +++ b/Documentation/virt/hyperv/coco.rst
> @@ -178,7 +178,7 @@ These Hyper-V and VMBus memory pages are marked as decrypted:
>
>  * VMBus monitor pages
>
> -* Synthetic interrupt controller (synic) related pages (unless supplied by
> +* Synthetic interrupt controller (SynIC) related pages (unless supplied by
>    the paravisor)
>
>  * Per-cpu hypercall input and output pages (unless running with a paravisor)
> @@ -232,6 +232,143 @@ with arguments explicitly describing the access. See
>  _hv_pcifront_read_config() and _hv_pcifront_write_config() and the
>  "use_calls" flag indicating to use hypercalls.
>
> +Confidential VMBus
> +------------------
> +The confidential VMBus enables the confidential guest not to interact with
> +the untrusted host partition and the untrusted hypervisor. Instead, the guest
> +relies on the trusted paravisor to communicate with the devices processing
> +sensitive data. The hardware (SNP or TDX) encrypts the guest memory and the
> +register state while measuring the paravisor image using the platform security
> +processor to ensure trusted and confidential computing.
> +
> +Confidential VMBus provides a secure communication channel between the guest
> +and the paravisor, ensuring that sensitive data is protected from hypervisor-
> +level access through memory encryption and register state isolation.
> +
> +Confidential VMBus is an extension of Confidential Computing (CoCo) VMs
> +(a.k.a. "Isolated" VMs in Hyper-V terminology). Without Confidential VMBus,
> +guest VMBus device drivers (the "VSC"s in VMBus terminology) communicate
> +with VMBus servers (the VSPs) running on the Hyper-V host. The
> +communication must be through memory that has been decrypted so the
> +host can access it. With Confidential VMBus, one or more of the VSPs reside
> +in the trusted paravisor layer in the guest VM. Since the paravisor layer also
> +operates in encrypted memory, the memory used for communication with
> +such VSPs does not need to be decrypted and thereby exposed to the
> +Hyper-V host. The paravisor is responsible for communicating securely
> +with the Hyper-V host as necessary.
> +
> +The data is transferred directly between the VM and a vPCI device (a.k.a.
> +a PCI pass-thru device, see :doc:`vpci`) that is directly assigned to VTL2
> +and that supports encrypted memory. In such a case, neither the host partition
> +nor the hypervisor has any access to the data. The guest needs to establish
> +a VMBus connection only with the paravisor for the channels that process
> +sensitive data, and the paravisor abstracts the details of communicating
> +with the specific devices away providing the guest with the well-established
> +VSP (Virtual Service Provider) interface that has had support in the Hyper-V
> +drivers for a decade.
> +
> +In the case the device does not support encrypted memory, the paravisor
> +provides bounce-buffering, and although the data is not encrypted, the backing
> +pages aren't mapped into the host partition through SLAT. While not impossible,
> +it becomes much more difficult for the host partition to exfiltrate the data
> +than it would be with a conventional VMBus connection where the host partition
> +has direct access to the memory used for communication.
> +
> +Here is the data flow for a conventional VMBus connection (`C` stands for the
> +client or VSC, `S` for the server or VSP, the `DEVICE` is a physical one, might
> +be with multiple virtual functions)::
> +
> +  +---- GUEST ----+       +----- DEVICE ----+        +----- HOST -----+
> +  |               |       |                 |        |                |
> +  |               |       |                 |        |                |
> +  |               |       |                 ==========                |
> +  |               |       |                 |        |                |
> +  |               |       |                 |        |                |
> +  |               |       |                 |        |                |
> +  +----- C -------+       +-----------------+        +------- S ------+
> +         ||                                                   ||
> +         ||                                                   ||
> +  +------||------------------ VMBus --------------------------||------+
> +  |                     Interrupts, MMIO                              |
> +  +-------------------------------------------------------------------+
> +
> +and the Confidential VMBus connection::
> +
> +  +---- GUEST --------------- VTL0 ------+               +-- DEVICE --+
> +  |                                      |               |            |
> +  | +- PARAVISOR --------- VTL2 -----+   |               |            |
> +  | |     +-- VMBus Relay ------+    ====+================            |
> +  | |     |   Interrupts, MMIO  |    |   |               |            |
> +  | |     +-------- S ----------+    |   |               +------------+
> +  | |               ||               |   |
> +  | +---------+     ||               |   |
> +  | |  Linux  |     ||    OpenHCL    |   |
> +  | |  kernel |     ||               |   |
> +  | +---- C --+-----||---------------+   |
> +  |       ||        ||                   |
> +  +-------++------- C -------------------+               +------------+
> +          ||                                             |    HOST    |
> +          ||                                             +---- S -----+
> +  +-------||----------------- VMBus ---------------------------||-----+
> +  |                     Interrupts, MMIO                              |
> +  +-------------------------------------------------------------------+
> +
> +An implementation of the VMBus relay that offers the Confidential VMBus
> +channels is available in the OpenVMM project as a part of the OpenHCL
> +paravisor. Please refer to
> +
> +  *
> https://openvmm.dev/
> %2F&data=05%7C02%7C%7Ceb6de4b7295c4e8a8ab908de02cc219c%7C84df9e7fe9
> f640afb435aaaaaaaaaaaa%7C1%7C0%7C638951272987274372%7CUnknown%7CT
> WFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIs
> IkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=9iTXf52zezdCCpMv4
> wv1S1AkWvnokRyXJD7hF3vU6h4%3D&reserved=0, and
> +  *
> https://github.com/
> microsoft%2Fopenvmm&data=05%7C02%7C%7Ceb6de4b7295c4e8a8ab908de02cc2
> 19c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638951272987295766
> %7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwM
> CIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=r
> Dp0el9NwDfSpRLSTmdLQgIqXqgLxrFrWJFcZcgb3Zk%3D&reserved=0
> +
> +for more information about the OpenHCL paravisor.
> +
> +A guest that is running with a paravisor must determine at runtime if
> +Confidential VMBus is supported by the current paravisor.The x86_64-specific

Nit: Missing a space before "The".

> +approach relies on the CPUID Virtualization Stack leaf; the ARM64 implementation
> +is expected to support the Confidential VMBus unconditionally when running
> +the ARM CCA guests.

s/the ARM CCA/ARM CCA/

> +
> +Confidential VMBus is a characteristic of the VMBus connection as a whole,
> +and of each VMBus channel that is created. When a Confidential VMBus
> +connection is established, the paravisor provides the guest the message-passing
> +path that is used for VMBus device creation and deletion, and it provides a
> +per-CPU synthetic interrupt controller (SynIC) just like the SynIC that is
> +offered by the Hyper-V host. Each VMBus device that is offered to the guest
> +indicates the degree to which it participates in Confidential VMBus. The offer
> +indicates if the device uses encrypted ring buffers, and if the device uses
> +encrypted memory for DMA that is done outside the ring buffer. These settings
> +may be different for different devices using the same Confidential VMBus
> +connection.
> +
> +Although these settings are separate, in practice it'll always be encrypted
> +ring buffer only, or both encrypted ring buffer and external data. If a channel
> +is offered by the paravisor with confidential VMBus, the ring buffer can always
> +be encrypted since it's strictly for communication between the VTL2 paravisor
> +and the VTL0 guest. However, other memory regions are often used for e.g. DMA,
> +so they need to be accessible by the underlying hardware, and must be
> +unencrypted (unless the device supports encrypted memory). Currently, there are
> +not any VSPs in OpenHCL that support encrypted external memory, but future
> +versions are expected to enable this capability.
> +
> +Because some devices on a Confidential VMBus may require decrypted ring buffers
> +and DMA transfers, the guest must interact with two SynICs -- the one provided
> +by the paravisor and the one provided by the Hyper-V host when Confidential
> +VMBus is not offered. Interrupts are always signaled by the paravisor SynIC,
> +but the guest must check for messages and for channel interrupts on both SynICs.
> +
> +In the case of a confidential VMBus, regular SynIC access by the guest is
> +intercepted by the paravisor (this includes various MSRs such as the SIMP and
> +SIEFP, as well as hypercalls like HvPostMessage and HvSignalEvent). If the
> +guest actually wants to communicate with the hypervisor, it has to use special
> +mechanisms (GHCB page on SNP, or tdcall on TDX). Messages can be of either
> +kind: with confidential VMBus, messages use the paravisor SynIC, and if the
> +guest chose to communicate directly to the hypervisor, they use the hypervisor
> +SynIC. For interrupt signaling, some channels may be running on the host
> +(non-confidential, using the VMBus relay) and use the hypervisor SynIC, and
> +some on the paravisor and use its SynIC. The RelIDs are coordinated by the
> +OpenHCL VMBus server and are guaranteed to be unique regardless of whether
> +the channel originated on the host or the paravisor.
> +
>  load_unaligned_zeropad()
>  ------------------------
>  When transitioning memory between encrypted and decrypted, the caller of
> --
> 2.43.0
>

RE: [PATCH hyperv-next v6 05/17] arch/x86: mshyperv: Trap on access for some synthetic MSRs

[Michael Kelley]

From: Roman Kisel <romank@linux.microsoft.com> Sent: Friday, October 3, 2025 3:27 PM
> 
> hv_set_non_nested_msr() has special handling for SINT MSRs
> when a paravisor is present. In addition to updating the MSR on the
> host, the mirror MSR in the paravisor is updated, including with the
> proxy bit. But with Confidential VMBus, the proxy bit must not be
> used, so add a special case to skip it.
> 
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
> Reviewed-by: Tianyu Lan <tiala@microsoft.com>
> ---
>  arch/x86/kernel/cpu/mshyperv.c | 29 +++++++++++++++++++++++++----
>  drivers/hv/hv_common.c         |  5 +++++
>  include/asm-generic/mshyperv.h |  1 +
>  3 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index af5a3bbbca9f..b410b930938a 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -28,6 +28,7 @@
>  #include <asm/apic.h>
>  #include <asm/timer.h>
>  #include <asm/reboot.h>
> +#include <asm/msr.h>
>  #include <asm/nmi.h>
>  #include <clocksource/hyperv_timer.h>
>  #include <asm/msr.h>
> @@ -38,6 +39,12 @@
>  bool hv_nested;
>  struct ms_hyperv_info ms_hyperv;
> 
> +/*
> + * When running with the paravisor, controls proxying the synthetic interrupts
> + * from the host
> + */
> +static bool hv_para_sint_proxy;

This needs to move down a few lines and be under the #if IS_ENABLED(CONFIG_HYPERV)
in order to eliminate the "unused variable" warning reported by the kernel test robot.

> +
>  /* Used in modules via hv_do_hypercall(): see arch/x86/include/asm/mshyperv.h */
>  bool hyperv_paravisor_present __ro_after_init;
>  EXPORT_SYMBOL_GPL(hyperv_paravisor_present);
> @@ -79,17 +86,31 @@ EXPORT_SYMBOL_GPL(hv_get_non_nested_msr);
>  void hv_set_non_nested_msr(unsigned int reg, u64 value)
>  {
>  	if (hv_is_synic_msr(reg) && ms_hyperv.paravisor_present) {
> +		/* The hypervisor will get the intercept. */
>  		hv_ivm_msr_write(reg, value);
> 
> -		/* Write proxy bit via wrmsl instruction */
> -		if (hv_is_sint_msr(reg))
> -			wrmsrq(reg, value | 1 << 20);
> +		/* Using wrmsrq so the following goes to the paravisor. */
> +		if (hv_is_sint_msr(reg)) {
> +			union hv_synic_sint sint = { .as_uint64 = value };
> +
> +			sint.proxy = hv_para_sint_proxy;
> +			native_wrmsrq(reg, sint.as_uint64);
> +		}
>  	} else {
> -		wrmsrq(reg, value);
> +		native_wrmsrq(reg, value);
>  	}
>  }
>  EXPORT_SYMBOL_GPL(hv_set_non_nested_msr);
> 
> +/*
> + * Enable or disable proxying synthetic interrupts
> + * to the paravisor.
> + */
> +void hv_para_set_sint_proxy(bool enable)
> +{
> +	hv_para_sint_proxy = enable;
> +}
> +
>  /*
>   * Get the SynIC register value from the paravisor.
>   */
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 8756ca834546..1a5c7a358971 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -716,6 +716,11 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64
> param2)
>  }
>  EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
> 
> +void __weak hv_para_set_sint_proxy(bool enable)
> +{
> +}
> +EXPORT_SYMBOL_GPL(hv_para_set_sint_proxy);
> +
>  u64 __weak hv_para_get_synic_register(unsigned int reg)
>  {
>  	return ~0ULL;
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index c010059f1518..3955ba6d60b8 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -298,6 +298,7 @@ bool hv_is_isolation_supported(void);
>  bool hv_isolation_type_snp(void);
>  u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
>  u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
> +void hv_para_set_sint_proxy(bool enable);
>  u64 hv_para_get_synic_register(unsigned int reg);
>  void hv_para_set_synic_register(unsigned int reg, u64 val);
>  void hyperv_cleanup(void);
> --
> 2.43.0
> 

Re: [PATCH hyperv-next v6 05/17] arch/x86: mshyperv: Trap on access for some synthetic MSRs

[Roman Kisel]

On 10/6/2025 9:55 AM, Michael Kelley wrote:
> From: Roman Kisel <romank@linux.microsoft.com> Sent: Friday, October 3, 2025 3:27 PM

[...]

>> +/*
>> + * When running with the paravisor, controls proxying the synthetic interrupts
>> + * from the host
>> + */
>> +static bool hv_para_sint_proxy;
> 
> This needs to move down a few lines and be under the #if IS_ENABLED(CONFIG_HYPERV)
> in order to eliminate the "unused variable" warning reported by the kernel test robot.

Thanks, Michael, will do!

[...]
-- 
Thank you,
Roman

Re: [PATCH hyperv-next v6 00/17] Confidential VMBus

[Roman Kisel]

On 10/6/2025 9:55 AM, Michael Kelley wrote:
> From: Roman Kisel <romank@linux.microsoft.com> Sent: Friday, October 3, 2025 3:27 PM

[...]

>>   include/linux/hyperv.h             |  69 ++++--
>>   15 files changed, 793 insertions(+), 306 deletions(-)
>>
> 
> Nice! The net lines of code added is now 487, vs. 591
> lines added in v5 of this series.
> 

Thanks, I appreciate your help throughout the multiple versions very
much!!

> Modulo the contradiction above in this cover letter, the two typos in
> the documentation in Patch 1, and the simple fix for the error reported
> by the kernel test robot for Patch 5, I'm happy with this entire series.

I'll wait few days just in case and will send out the fixed series :)

> For the series,
> 
> Reviewed-by: Michael Kelley <mhklinux@outlook.com>

-- 
Thank you,
Roman

Re: [PATCH hyperv-next v6 01/17] Documentation: hyperv: Confidential VMBus

[Bagas Sanjaya]

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On Fri, Oct 03, 2025 at 03:26:54PM -0700, Roman Kisel wrote:
> +The data is transferred directly between the VM and a vPCI device (a.k.a.
> +a PCI pass-thru device, see :doc:`vpci`) that is directly assigned to VTL2
> +and that supports encrypted memory. In such a case, neither the host partition

Nit: You can also write the cross-reference simply as vpci.rst.

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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Re: [PATCH hyperv-next v6 01/17] Documentation: hyperv: Confidential VMBus

[Roman Kisel]

On 10/6/2025 7:23 PM, Bagas Sanjaya wrote:
> On Fri, Oct 03, 2025 at 03:26:54PM -0700, Roman Kisel wrote:
>> +The data is transferred directly between the VM and a vPCI device (a.k.a.
>> +a PCI pass-thru device, see :doc:`vpci`) that is directly assigned to VTL2
>> +and that supports encrypted memory. In such a case, neither the host partition
> 
> Nit: You can also write the cross-reference simply as vpci.rst.
> 

Thanks for helping out! I could not find that way of cross-referencing
in the Sphinx documentation though:
https://www.sphinx-doc.org/en/master/usage/referencing.html#cross-referencing-documents

I tried it out anyway. The suggestion worked out only for the HTML
documentation, and would not work for the PDF one. Options attempted:

1. vpci
2. vpci.rst
3. Documentation/virt/hyperv/vpci
4. Documentation/virt/hyperv/vpci.rst

and neither would produce a hyperlink inside virt.pdf. Options 2 & 4
generated a hyperlink in HTML.

The

| :doc:`vpci`

directive I've used produces a hyperlink both for HTML & PDF and is
mentioned in the Sphinx documentation linked above.

Please let me know if I misunderstood your suggestion and/or tested
it in a wrong way. So far, it appears that it works only for HTML.

> Thanks.
> 

-- 
Thank you,
Roman

Re: [PATCH hyperv-next v6 01/17] Documentation: hyperv: Confidential VMBus

[Bagas Sanjaya]

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On Tue, Oct 07, 2025 at 01:38:02PM -0700, Roman Kisel wrote:
> 
> 
> On 10/6/2025 7:23 PM, Bagas Sanjaya wrote:
> > On Fri, Oct 03, 2025 at 03:26:54PM -0700, Roman Kisel wrote:
> > > +The data is transferred directly between the VM and a vPCI device (a.k.a.
> > > +a PCI pass-thru device, see :doc:`vpci`) that is directly assigned to VTL2
> > > +and that supports encrypted memory. In such a case, neither the host partition
> > 
> > Nit: You can also write the cross-reference simply as vpci.rst.
> > 
> 
> Thanks for helping out! I could not find that way of cross-referencing
> in the Sphinx documentation though:
> https://www.sphinx-doc.org/en/master/usage/referencing.html#cross-referencing-documents

That's kernel-specific extension (see Documentation/doc-guide/sphinx.rst).

> 
> I tried it out anyway. The suggestion worked out only for the HTML
> documentation, and would not work for the PDF one. Options attempted:
> 
> 1. vpci
> 2. vpci.rst
> 3. Documentation/virt/hyperv/vpci
> 4. Documentation/virt/hyperv/vpci.rst
> 
> and neither would produce a hyperlink inside virt.pdf. Options 2 & 4
> generated a hyperlink in HTML.

That's it.

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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Re: [PATCH hyperv-next v6 01/17] Documentation: hyperv: Confidential VMBus

[Roman Kisel]

On 10/7/2025 4:56 PM, Bagas Sanjaya wrote:
> On Tue, Oct 07, 2025 at 01:38:02PM -0700, Roman Kisel wrote:
>>
>>
>> On 10/6/2025 7:23 PM, Bagas Sanjaya wrote:
>>> On Fri, Oct 03, 2025 at 03:26:54PM -0700, Roman Kisel wrote:
>>>> +The data is transferred directly between the VM and a vPCI device (a.k.a.
>>>> +a PCI pass-thru device, see :doc:`vpci`) that is directly assigned to VTL2
>>>> +and that supports encrypted memory. In such a case, neither the host partition
>>>
>>> Nit: You can also write the cross-reference simply as vpci.rst.
>>>
>>
>> Thanks for helping out! I could not find that way of cross-referencing
>> in the Sphinx documentation though:
>> https://www.sphinx-doc.org/en/master/usage/referencing.html#cross-referencing-documents
> 
> That's kernel-specific extension (see Documentation/doc-guide/sphinx.rst).
> 

Thanks, got it! So far, in my experience, that doesn't work for PDFs.

>>
>> I tried it out anyway. The suggestion worked out only for the HTML
>> documentation, and would not work for the PDF one. Options attempted:
>>
>> 1. vpci
>> 2. vpci.rst
>> 3. Documentation/virt/hyperv/vpci
>> 4. Documentation/virt/hyperv/vpci.rst
>>
>> and neither would produce a hyperlink inside virt.pdf. Options 2 & 4
>> generated a hyperlink in HTML.
> 
> That's it.
> 
> Thanks.
> 

I found in the document you referred to ("1.3.4 Cross-referencing") that

"Cross-referencing from one documentation page to another can be done
simply by writing the path to the document file, no special syntax
required."

 From the document, that relies on some additional processing within the
kernel tree (above you mentioned that, too), and that doesn't seem to
work for PDFs. I'll stick to the :doc: syntax then used in the patch.
I'll investigate separately why the additional processing that allows to
simplify syntax works for HTMLs only.

Appreciate your help very much!

-- 
Thank you,
Roman

Re: [PATCH hyperv-next v6 01/17] Documentation: hyperv: Confidential VMBus

[Bagas Sanjaya]

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On Wed, Oct 08, 2025 at 03:11:35PM -0700, Roman Kisel wrote:
> 
> 
> On 10/7/2025 4:56 PM, Bagas Sanjaya wrote:
> > On Tue, Oct 07, 2025 at 01:38:02PM -0700, Roman Kisel wrote:
> > > 
> > > 
> > > On 10/6/2025 7:23 PM, Bagas Sanjaya wrote:
> > > > On Fri, Oct 03, 2025 at 03:26:54PM -0700, Roman Kisel wrote:
> > > > > +The data is transferred directly between the VM and a vPCI device (a.k.a.
> > > > > +a PCI pass-thru device, see :doc:`vpci`) that is directly assigned to VTL2
> > > > > +and that supports encrypted memory. In such a case, neither the host partition
> > > > 
> > > > Nit: You can also write the cross-reference simply as vpci.rst.
> > > > 
> > > 
> > > Thanks for helping out! I could not find that way of cross-referencing
> > > in the Sphinx documentation though:
> > > https://www.sphinx-doc.org/en/master/usage/referencing.html#cross-referencing-documents
> > 
> > That's kernel-specific extension (see Documentation/doc-guide/sphinx.rst).
> > 
> 
> Thanks, got it! So far, in my experience, that doesn't work for PDFs.
> 
> > > 
> > > I tried it out anyway. The suggestion worked out only for the HTML
> > > documentation, and would not work for the PDF one. Options attempted:
> > > 
> > > 1. vpci
> > > 2. vpci.rst
> > > 3. Documentation/virt/hyperv/vpci
> > > 4. Documentation/virt/hyperv/vpci.rst
> > > 
> > > and neither would produce a hyperlink inside virt.pdf. Options 2 & 4
> > > generated a hyperlink in HTML.
> > 
> > That's it.
> > 
> > Thanks.
> > 
> 
> I found in the document you referred to ("1.3.4 Cross-referencing") that
> 
> "Cross-referencing from one documentation page to another can be done
> simply by writing the path to the document file, no special syntax
> required."
> 
> From the document, that relies on some additional processing within the
> kernel tree (above you mentioned that, too), and that doesn't seem to
> work for PDFs. I'll stick to the :doc: syntax then used in the patch.
> I'll investigate separately why the additional processing that allows to
> simplify syntax works for HTMLs only.

OK, thanks!

-- 
An old man doll... just what I always wanted! - Clara

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