Documentation: kvm/sev: clarify usage of KVM_MEMORY_ENCRYPT_OP
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>
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@ -49,12 +49,13 @@ defined in the CPUID 0x8000001f[ecx] field.
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The KVM_MEMORY_ENCRYPT_OP ioctl
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===============================
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The main ioctl to access SEV is KVM_MEMORY_ENCRYPT_OP. If the argument
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to KVM_MEMORY_ENCRYPT_OP is NULL, the ioctl returns 0 if SEV is enabled
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and ``ENOTTY`` if it is disabled (on some older versions of Linux,
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the ioctl runs normally even with a NULL argument, and therefore will
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likely return ``EFAULT``). If non-NULL, the argument to KVM_MEMORY_ENCRYPT_OP
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must be a struct kvm_sev_cmd::
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The main ioctl to access SEV is KVM_MEMORY_ENCRYPT_OP, which operates on
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the VM file descriptor. If the argument to KVM_MEMORY_ENCRYPT_OP is NULL,
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the ioctl returns 0 if SEV is enabled and ``ENOTTY`` if it is disabled
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(on some older versions of Linux, the ioctl tries to run normally even
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with a NULL argument, and therefore will likely return ``EFAULT`` instead
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of zero if SEV is enabled). If non-NULL, the argument to
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KVM_MEMORY_ENCRYPT_OP must be a struct kvm_sev_cmd::
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struct kvm_sev_cmd {
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__u32 id;
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