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KVM: Rework KVM_CAP_GUEST_MEMFD_MMAP into KVM_CAP_GUEST_MEMFD_FLAGS

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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>
This commit is contained in:
Sean Christopherson
2025-10-03 16:25:54 -07:00
parent 034417c143
commit d2042d8f96
4 changed files with 19 additions and 13 deletions
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7
virt/kvm/kvm_main.c
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@@ -4928,8 +4928,11 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
#ifdef CONFIG_KVM_GUEST_MEMFD
case KVM_CAP_GUEST_MEMFD:
return 1;
case KVM_CAP_GUEST_MEMFD_MMAP:
return !kvm || kvm_arch_supports_gmem_mmap(kvm);
case KVM_CAP_GUEST_MEMFD_FLAGS:
if (!kvm || kvm_arch_supports_gmem_mmap(kvm))
return GUEST_MEMFD_FLAG_MMAP;
return 0;
#endif
default:
break;