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| author | Paolo Bonzini <pbonzini@redhat.com> | 2025-10-18 10:25:43 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2025-10-18 10:25:43 +0200 |
| commit | 4361f5aa8bfcecbab3fc8db987482b9e08115a6a (patch) | |
| tree | 7fbee6760544a527348a11775c286105e47f73d2 /Documentation | |
| parent | Merge tag 'kvmarm-fixes-6.18-1' of git://git.kernel.org/pub/scm/linux/kernel/... (diff) | |
| parent | KVM: selftests: Verify that reads to inaccessible guest_memfd VMAs SIGBUS (diff) | |
| download | linux-4361f5aa8bfcecbab3fc8db987482b9e08115a6a.tar.gz linux-4361f5aa8bfcecbab3fc8db987482b9e08115a6a.zip | |
Merge tag 'kvm-x86-fixes-6.18-rc2' of https://github.com/kvm-x86/linux into HEAD
KVM x86 fixes for 6.18:
- Expand the KVM_PRE_FAULT_MEMORY selftest to add a regression test for the
bug fixed by commit 3ccbf6f47098 ("KVM: x86/mmu: Return -EAGAIN if userspace
deletes/moves memslot during prefault")
- Don't try to get PMU capabbilities from perf when running a CPU with hybrid
CPUs/PMUs, as perf will rightly WARN.
- Rework KVM_CAP_GUEST_MEMFD_MMAP (newly introduced in 6.18) into a more
generic KVM_CAP_GUEST_MEMFD_FLAGS
- Add a guest_memfd INIT_SHARED flag and require userspace to explicitly set
said flag to initialize memory as SHARED, irrespective of MMAP. The
behavior merged in 6.18 is that enabling mmap() implicitly initializes
memory as SHARED, which would result in an ABI collision for x86 CoCo VMs
as their memory is currently always initialized PRIVATE.
- Allow mmap() on guest_memfd for x86 CoCo VMs, i.e. on VMs with private
memory, to enable testing such setups, i.e. to hopefully flush out any
other lurking ABI issues before 6.18 is officially released.
- Add testcases to the guest_memfd selftest to cover guest_memfd without MMAP,
and host userspace accesses to mmap()'d private memory.
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 4973c74db5c6..57061fa29e6a 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6437,9 +6437,18 @@ most one mapping per page, i.e. binding multiple memory regions to a single guest_memfd range is not allowed (any number of memory regions can be bound to a single guest_memfd file, but the bound ranges must not overlap). -When the capability KVM_CAP_GUEST_MEMFD_MMAP is supported, the 'flags' field -supports GUEST_MEMFD_FLAG_MMAP. Setting this flag on guest_memfd creation -enables mmap() and faulting of guest_memfd memory to host userspace. +The capability KVM_CAP_GUEST_MEMFD_FLAGS enumerates the `flags` that can be +specified via KVM_CREATE_GUEST_MEMFD. Currently defined flags: + + ============================ ================================================ + GUEST_MEMFD_FLAG_MMAP Enable using mmap() on the guest_memfd file + descriptor. + GUEST_MEMFD_FLAG_INIT_SHARED Make all memory in the file shared during + KVM_CREATE_GUEST_MEMFD (memory files created + without INIT_SHARED will be marked private). + Shared memory can be faulted into host userspace + page tables. Private memory cannot. + ============================ ================================================ When the KVM MMU performs a PFN lookup to service a guest fault and the backing guest_memfd has the GUEST_MEMFD_FLAG_MMAP set, then the fault will always be |