From 3988bd2723de407ae90fa7a6f6029b4e60238c58 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 1 May 2026 13:22:29 -0700 Subject: [PATCH] KVM: SEV: Ignore Port I/O requests of length '0' 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: 291bd20d5d88 ("KVM: SVM: Add initial support for a VMGEXIT VMEXIT") Cc: stable@vger.kernel.org Reviewed-by: Tom Lendacky Signed-off-by: Sean Christopherson Message-ID: <20260501202250.2115252-5-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/sev.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index e6579ca9f364..52703c954856 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -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;