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KVM: SEV: Ignore Port I/O requests of length '0'

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Explicitly ignore Port I/O requests of length '0' (or count '0'), so that
setting up the software scratch area (and other code) doesn't have to
worry about underflowing the length, and to allow for WARNing on trying
to configure the scratch area with len==0.

Fixes: 291bd20d5d ("KVM: SVM: Add initial support for a VMGEXIT VMEXIT")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2026-05-01 13:22:29 -07:00 committed by Paolo Bonzini
parent dcf1b2d4b0
commit 3988bd2723
1 changed files with 8 additions and 0 deletions
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8
arch/x86/kvm/svm/sev.c
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@ -4585,6 +4585,11 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
control->exit_info_1, control->exit_info_2);
ret = -EINVAL;
break;
case SVM_EXIT_IOIO:
if (!((control->exit_info_1 & SVM_IOIO_SIZE_MASK) >> SVM_IOIO_SIZE_SHIFT))
return 1;
fallthrough;
default:
ret = svm_invoke_exit_handler(vcpu, control->exit_code);
}
@ -4605,6 +4610,9 @@ int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in)
if (unlikely(check_mul_overflow(count, size, &bytes)))
return -EINVAL;
if (!bytes)
return 1;
r = setup_vmgexit_scratch(svm, in, bytes);
if (r)
return r;