Commit c532f290 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
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KVM: SVM: Explicitly require DECODEASSISTS to enable SEV support 



Add a sanity check on DECODEASSIST being support if SEV is supported, as
KVM cannot read guest private memory and thus relies on the CPU to
provide the instruction byte stream on #NPF for emulation.  The intent of
the check is to document the dependency, it should never fail in practice
as producing hardware that supports SEV but not DECODEASSISTS would be
non-sensical.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarLiam Merwick <liam.merwick@oracle.com>
Message-Id: <20220120010719.711476-5-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 0b0be065

arch/x86/kvm/svm/sev.c

+7 −2
Original line number Diff line number Diff line
@@ -2100,8 +2100,13 @@ void __init sev_hardware_setup(void) 
	if (!sev_enabled || !npt_enabled)

		goto out;



	/* Does the CPU support SEV? */

	if (!boot_cpu_has(X86_FEATURE_SEV))

	/*

	 * SEV must obviously be supported in hardware.  Sanity check that the

	 * CPU supports decode assists, which is mandatory for SEV guests to

	 * support instruction emulation.

	 */

	if (!boot_cpu_has(X86_FEATURE_SEV) ||

	    WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS)))

		goto out;



	/* Retrieve SEV CPUID information */