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.
Allow mmap() on guest_memfd instances for x86 VMs with private memory as
the need to track private vs. shared state in the guest_memfd instance is
only pertinent to INIT_SHARED. Doing mmap() on private memory isn't
terrible useful (yet!), but it's now possible, and will be desirable when
guest_memfd gains support for other VMA-based syscalls, e.g. mbind() to
set NUMA policy.
Lift the restriction now, before MMAP support is officially released, so
that KVM doesn't need to add another capability to enumerate support for
mmap() on private memory.
Fixes: 3d3a04fad25a ("KVM: Allow and advertise support for host mmap() on guest_memfd files")
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Tested-by: Ackerley Tng <ackerleytng@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20251003232606.4070510-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add KVM_GENERIC_MMU_NOTIFIER as a dependency for selecting KVM_GUEST_MEMFD,
as guest_memfd relies on kvm_mmu_invalidate_{begin,end}(), which are
defined if and only if the generic mmu_notifier implementation is enabled.
The missing dependency is currently benign as s390 is the only KVM arch
that doesn't utilize the generic mmu_notifier infrastructure, and s390
doesn't currently support guest_memfd.
Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20251003232606.4070510-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
When invalidating gmem ranges, e.g. in response to PUNCH_HOLE, process all
possible range types (PRIVATE vs. SHARED) for the gmem instance. Since
since guest_memfd doesn't yet support in-place conversions, simply pivot
on INIT_SHARED as a gmem instance can currently only have private or shared
memory, not both.
Failure to mark shared GPAs for invalidation is benign in the current code
base, as only x86's TDX consumes KVM_FILTER_{PRIVATE,SHARED}, and TDX
doesn't yet support INIT_SHARED with guest_memfd. However, invalidating
only private GPAs is conceptually wrong and a lurking bug, e.g. could
result in missed invalidations if ARM starts filtering invalidations based
on attributes.
Fixes: 3d3a04fad25a ("KVM: Allow and advertise support for host mmap() on guest_memfd files")
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20251003232606.4070510-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add a guest_memfd flag to allow userspace to state that the underlying
memory should be configured to be initialized as shared, and reject user
page faults if the guest_memfd instance's memory isn't shared. Because
KVM doesn't yet support in-place private<=>shared conversions, all
guest_memfd memory effectively follows the initial state.
Alternatively, KVM could deduce the initial state based on MMAP, which for
all intents and purposes is what KVM currently does. However, implicitly
deriving the default state based on MMAP will result in a messy ABI when
support for in-place conversions is added.
For x86 CoCo VMs, which don't yet support MMAP, memory is currently private
by default (otherwise the memory would be unusable). If MMAP implies
memory is shared by default, then the default state for CoCo VMs will vary
based on MMAP, and from userspace's perspective, will change when in-place
conversion support is added. I.e. to maintain guest<=>host ABI, userspace
would need to immediately convert all memory from shared=>private, which
is both ugly and inefficient. The inefficiency could be avoided by adding
a flag to state that memory is _private_ by default, irrespective of MMAP,
but that would lead to an equally messy and hard to document ABI.
Bite the bullet and immediately add a flag to control the default state so
that the effective behavior is explicit and straightforward.
Fixes: 3d3a04fad25a ("KVM: Allow and advertise support for host mmap() on guest_memfd files")
Cc: David Hildenbrand <david@redhat.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Tested-by: Ackerley Tng <ackerleytng@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20251003232606.4070510-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Rework the not-yet-released KVM_CAP_GUEST_MEMFD_MMAP into a more generic KVM_CAP_GUEST_MEMFD_FLAGS capability so that adding new flags doesn't require a new capability, and so that developers aren't tempted to bundle multiple flags into a single capability. Note, kvm_vm_ioctl_check_extension_generic() can only return a 32-bit value, but that limitation can be easily circumvented by adding e.g. KVM_CAP_GUEST_MEMFD_FLAGS2 in the unlikely event guest_memfd supports more than 32 flags. Reviewed-by: Ackerley Tng <ackerleytng@google.com> Tested-by: Ackerley Tng <ackerleytng@google.com> Reviewed-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/r/20251003232606.4070510-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>
Pull hyperv updates from Wei Liu: - Unify guest entry code for KVM and MSHV (Sean Christopherson) - Switch Hyper-V MSI domain to use msi_create_parent_irq_domain() (Nam Cao) - Add CONFIG_HYPERV_VMBUS and limit the semantics of CONFIG_HYPERV (Mukesh Rathor) - Add kexec/kdump support on Azure CVMs (Vitaly Kuznetsov) - Deprecate hyperv_fb in favor of Hyper-V DRM driver (Prasanna Kumar T S M) - Miscellaneous enhancements, fixes and cleanups (Abhishek Tiwari, Alok Tiwari, Nuno Das Neves, Wei Liu, Roman Kisel, Michael Kelley) * tag 'hyperv-next-signed-20251006' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: hyperv: Remove the spurious null directive line MAINTAINERS: Mark hyperv_fb driver Obsolete fbdev/hyperv_fb: deprecate this in favor of Hyper-V DRM driver Drivers: hv: Make CONFIG_HYPERV bool Drivers: hv: Add CONFIG_HYPERV_VMBUS option Drivers: hv: vmbus: Fix typos in vmbus_drv.c Drivers: hv: vmbus: Fix sysfs output format for ring buffer index Drivers: hv: vmbus: Clean up sscanf format specifier in target_cpu_store() x86/hyperv: Switch to msi_create_parent_irq_domain() mshv: Use common "entry virt" APIs to do work in root before running guest entry: Rename "kvm" entry code assets to "virt" to genericize APIs entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper mshv: Handle NEED_RESCHED_LAZY before transferring to guest x86/hyperv: Add kexec/kdump support on Azure CVMs Drivers: hv: Simplify data structures for VMBus channel close message Drivers: hv: util: Cosmetic changes for hv_utils_transport.c mshv: Add support for a new parent partition configuration clocksource: hyper-v: Skip unnecessary checks for the root partition hyperv: Add missing field to hv_output_map_device_interrupt
Rename the "kvm" entry code files and Kconfigs to use generic "virt" nomenclature so that the code can be reused by other hypervisors (or rather, their root/dom0 partition drivers), without incorrectly suggesting the code somehow relies on and/or involves KVM. No functional change intended. Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com> Signed-off-by: Wei Liu <wei.liu@kernel.org>
Rework the vast majority of KVM's exports to expose symbols only to KVM
submodules, i.e. to x86's kvm-{amd,intel}.ko and PPC's kvm-{pr,hv}.ko.
With few exceptions, KVM's exported APIs are intended (and safe) for KVM-
internal usage only.
Keep kvm_get_kvm(), kvm_get_kvm_safe(), and kvm_put_kvm() as normal
exports, as they are needed by VFIO, and are generally safe for external
usage (though ideally even the get/put APIs would be KVM-internal, and
VFIO would pin a VM by grabbing a reference to its associated file).
Implement a framework in kvm_types.h in anticipation of providing a macro
to restrict KVM-specific kernel exports, i.e. to provide symbol exports
for KVM if and only if KVM is built as one or more modules.
Link: https://lore.kernel.org/r/20250919003303.1355064-3-seanjc@google.com
Cc: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
KVM SVM changes for 6.18 - Require a minimum GHCB version of 2 when starting SEV-SNP guests via KVM_SEV_INIT2 so that invalid GHCB versions result in immediate errors instead of latent guest failures. - Add support for Secure TSC for SEV-SNP guests, which prevents the untrusted host from tampering with the guest's TSC frequency, while still allowing the the VMM to configure the guest's TSC frequency prior to launch. - Mitigate the potential for TOCTOU bugs when accessing GHCB fields by wrapping all accesses via READ_ONCE(). - Validate the XCR0 provided by the guest (via the GHCB) to avoid tracking a bogous XCR0 value in KVM's software model. - Save an SEV guest's policy if and only if LAUNCH_START fully succeeds to avoid leaving behind stale state (thankfully not consumed in KVM). - Explicitly reject non-positive effective lengths during SNP's LAUNCH_UPDATE instead of subtly relying on guest_memfd to do the "heavy" lifting. - Reload the pre-VMRUN TSC_AUX on #VMEXIT for SEV-ES guests, not the host's desired TSC_AUX, to fix a bug where KVM could clobber a different vCPU's TSC_AUX due to hardware not matching the value cached in the user-return MSR infrastructure. - Enable AVIC by default for Zen4+ if x2AVIC (and other prereqs) is supported, and clean up the AVIC initialization code along the way.