linux-toradex.git/Documentation/virt, branch v6.19-rc2

Merge tag 'hyperv-next-signed-20251207' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

2025-12-08T21:10:17+00:00

Pull hyperv updates from Wei Liu:

 - Enhancements to Linux as the root partition for Microsoft Hypervisor:
     - Support a new mode called L1VH, which allows Linux to drive the
       hypervisor running the Azure Host directly
     - Support for MSHV crash dump collection
     - Allow Linux's memory management subsystem to better manage guest
       memory regions
     - Fix issues that prevented a clean shutdown of the whole system on
       bare metal and nested configurations
     - ARM64 support for the MSHV driver
     - Various other bug fixes and cleanups

 - Add support for Confidential VMBus for Linux guest on Hyper-V

 - Secure AVIC support for Linux guests on Hyper-V

 - Add the mshv_vtl driver to allow Linux to run as the secure kernel in
   a higher virtual trust level for Hyper-V

* tag 'hyperv-next-signed-20251207' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: (58 commits)
  mshv: Cleanly shutdown root partition with MSHV
  mshv: Use reboot notifier to configure sleep state
  mshv: Add definitions for MSHV sleep state configuration
  mshv: Add support for movable memory regions
  mshv: Add refcount and locking to mem regions
  mshv: Fix huge page handling in memory region traversal
  mshv: Move region management to mshv_regions.c
  mshv: Centralize guest memory region destruction
  mshv: Refactor and rename memory region handling functions
  mshv: adjust interrupt control structure for ARM64
  Drivers: hv: use kmalloc_array() instead of kmalloc()
  mshv: Add ioctl for self targeted passthrough hvcalls
  Drivers: hv: Introduce mshv_vtl driver
  Drivers: hv: Export some symbols for mshv_vtl
  static_call: allow using STATIC_CALL_TRAMP_STR() from assembly
  mshv: Extend create partition ioctl to support cpu features
  mshv: Allow mappings that overlap in uaddr
  mshv: Fix create memory region overlap check
  mshv: add WQ_PERCPU to alloc_workqueue users
  Drivers: hv: Use kmalloc_array() instead of kmalloc()
  ...

Merge tag 'kvm-s390-next-6.19-1' of https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into HEAD

2025-12-02T17:58:47+00:00

- SCA rework
- VIRT_XFER_TO_GUEST_WORK support
- Operation exception forwarding support
- Cleanups

Merge tag 'kvmarm-6.19' of https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

2025-12-02T17:36:26+00:00

KVM/arm64 updates for 6.19

 - Support for userspace handling of synchronous external aborts (SEAs),
   allowing the VMM to potentially handle the abort in a non-fatal
   manner.

 - Large rework of the VGIC's list register handling with the goal of
   supporting more active/pending IRQs than available list registers in
   hardware. In addition, the VGIC now supports EOImode==1 style
   deactivations for IRQs which may occur on a separate vCPU than the
   one that acked the IRQ.

 - Support for FEAT_XNX (user / privileged execute permissions) and
   FEAT_HAF (hardware update to the Access Flag) in the software page
   table walkers and shadow MMU.

 - Allow page table destruction to reschedule, fixing long need_resched
   latencies observed when destroying a large VM.

 - Minor fixes to KVM and selftests

Merge tag 'kvm-riscv-6.19-1' of https://github.com/kvm-riscv/linux into HEAD

2025-12-02T17:35:25+00:00

KVM/riscv changes for 6.19

- SBI MPXY support for KVM guest
- New KVM_EXIT_FAIL_ENTRY_NO_VSFILE for the case when in-kernel
  AIA virtualization fails to allocate IMSIC VS-file
- Support enabling dirty log gradually in small chunks
- Fix guest page fault within HLV* instructions
- Flush VS-stage TLB after VCPU migration for Andes cores

Merge tag 'kvm-x86-svm-6.19' of https://github.com/kvm-x86/linux into HEAD

2025-11-26T08:48:39+00:00

KVM SVM changes for 6.19:

 - Fix a few missing "VMCB dirty" bugs.

 - Fix the worst of KVM's lack of EFER.LMSLE emulation.

 - Add AVIC support for addressing 4k vCPUs in x2AVIC mode.

 - Fix incorrect handling of selective CR0 writes when checking intercepts
   during emulation of L2 instructions.

 - Fix a currently-benign bug where KVM would clobber SPEC_CTRL[63:32] on
   VMRUN and #VMEXIT.

 - Fix a bug where KVM corrupt the guest code stream when re-injecting a soft
   interrupt if the guest patched the underlying code after the VM-Exit, e.g.
   when Linux patches code with a temporary INT3.

 - Add KVM_X86_SNP_POLICY_BITS to advertise supported SNP policy bits to
   userspace, and extend KVM "support" to all policy bits that don't require
   any actual support from KVM.

Merge tag 'kvm-x86-generic-6.19' of https://github.com/kvm-x86/linux into HEAD

2025-11-26T08:22:45+00:00

KVM generic changes for 6.19:

 - Use the recently-added WQ_PERCPU when creating the per-CPU workqueue for
   irqfd cleanup.

 - Fix a goof in the dirty ring documentation.

KVM: riscv: Support enabling dirty log gradually in small chunks

2025-11-24T04:25:36+00:00

There is already support of enabling dirty log gradually in small chunks
for x86 in commit 3c9bd4006bfc ("KVM: x86: enable dirty log gradually in
small chunks") and c862626 ("KVM: arm64: Support enabling dirty log
gradually in small chunks"). This adds support for riscv.

x86 and arm64 writes protect both huge pages and normal pages now, so
riscv protect also protects both huge pages and normal pages.

On a nested virtualization setup (RISC-V KVM running inside a QEMU VM
on an [Intel® Core™ i5-12500H] host), I did some tests with a 2G Linux
VM using different backing page sizes. The time taken for
memory_global_dirty_log_start in the L2 QEMU is listed below:

Page Size      Before    After Optimization
  4K            4490.23ms         31.94ms
  2M             48.97ms          45.46ms
  1G             28.40ms          30.93ms

Signed-off-by: Quan Zhou 
Signed-off-by: Dong Yang 
Reviewed-by: Anup Patel 
Link: https://lore.kernel.org/r/20251103062825.9084-1-dayss1224@gmail.com
Signed-off-by: Anup Patel

KVM: s390: Add capability that forwards operation exceptions

2025-11-21T09:26:03+00:00

Setting KVM_CAP_S390_USER_OPEREXEC will forward all operation
exceptions to user space. This also includes the 0x0000 instructions
managed by KVM_CAP_S390_USER_INSTR0. It's helpful if user space wants
to emulate instructions which do not (yet) have an opcode.

While we're at it refine the documentation for
KVM_CAP_S390_USER_INSTR0.

Signed-off-by: Janosch Frank 
Reviewed-by: Claudio Imbrenda 
Acked-by: Christian Borntraeger 
Signed-off-by: Janosch Frank

Documentation: hyperv: Confidential VMBus

2025-11-15T06:18:14+00:00

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

Signed-off-by: Roman Kisel 
Reviewed-by: Alok Tiwari 
Reviewed-by: Michael Kelley 
Signed-off-by: Wei Liu

KVM: x86: Document a virtualization gap for GIF on AMD CPUs

2025-11-13T21:15:15+00:00

According to the APM Volume #2, Section 15.17, Table 15-10 (24593—Rev.
3.42—March 2024), When "GIF==0", an "Debug exception or trap, due to
breakpoint register match" should be "Ignored and discarded".

KVM lacks any handling of this. Even when vGIF is enabled and vGIF==0,
the CPU does not ignore #DBs and relies on the VMM to do so.

Handling this is possible, but the complexity is unjustified given the
rarity of using HW breakpoints when GIF==0 (e.g. near VMRUN). KVM would
need to intercept the #DB, temporarily disable the breakpoint,
singe-step over the instruction (probably reusing NMI singe-stepping),
and re-enable the breakpoint.

Instead, document this as an erratum.

Signed-off-by: Yosry Ahmed 
Reviewed-by: Bagas Sanjaya 
Link: https://patch.msgid.link/20251030223757.2950309-1-yosry.ahmed@linux.dev
Signed-off-by: Sean Christopherson