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Documentation: kvm/sev: clarify usage of KVM_MEMORY_ENCRYPT_OP

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Explain that it operates on the VM file descriptor, and also clarify how
detection of SEV operates on old kernels predating commit 2da1ed62d5
("KVM: SVM: document KVM_MEM_ENCRYPT_OP, let userspace detect if SEV
is available").

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2024-03-18 12:11:41 -04:00
parent 19cebbab99
commit c20722c412
1 changed files with 7 additions and 6 deletions
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13
Documentation/virt/kvm/x86/amd-memory-encryption.rst
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@ -49,12 +49,13 @@ defined in the CPUID 0x8000001f[ecx] field.
The KVM_MEMORY_ENCRYPT_OP ioctl
===============================
The main ioctl to access SEV is KVM_MEMORY_ENCRYPT_OP. If the argument
to KVM_MEMORY_ENCRYPT_OP is NULL, the ioctl returns 0 if SEV is enabled
and ``ENOTTY`` if it is disabled (on some older versions of Linux,
the ioctl runs normally even with a NULL argument, and therefore will
likely return ``EFAULT``). If non-NULL, the argument to KVM_MEMORY_ENCRYPT_OP
must be a struct kvm_sev_cmd::
The main ioctl to access SEV is KVM_MEMORY_ENCRYPT_OP, which operates on
the VM file descriptor. If the argument to KVM_MEMORY_ENCRYPT_OP is NULL,
the ioctl returns 0 if SEV is enabled and ``ENOTTY`` if it is disabled
(on some older versions of Linux, the ioctl tries to run normally even
with a NULL argument, and therefore will likely return ``EFAULT`` instead
of zero if SEV is enabled). If non-NULL, the argument to
KVM_MEMORY_ENCRYPT_OP must be a struct kvm_sev_cmd::
struct kvm_sev_cmd {
__u32 id;