Re: [PATCH 1/8] KVM: SEV-ES: fix length of string I/O
From: Marc Orr <hidden>
Date: 2021-10-25 01:31:17
Also in:
kvm, lkml
Possibly related (same subject, not in this thread)
- 2021-10-18 · Re: [PATCH 1/8] KVM: SEV-ES: fix length of string I/O · Paolo Bonzini <pbonzini@redhat.com>
- 2021-10-18 · Re: [PATCH 1/8] KVM: SEV-ES: fix length of string I/O · Naresh Kamboju <hidden>
On Wed, Oct 13, 2021 at 9:56 AM Paolo Bonzini [off-list ref] wrote:
quoted hunk ↗ jump to hunk
The size of the data in the scratch buffer is not divided by the size of each port I/O operation, so vcpu->arch.pio.count ends up being larger than it should be by a factor of size. Cc: stable@vger.kernel.org Fixes: 7ed9abfe8e9f ("KVM: SVM: Support string IO operations for an SEV-ES guest") Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- arch/x86/kvm/svm/sev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index c36b5fe4c27c..e672493b5d8d 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c@@ -2583,7 +2583,7 @@ int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in) return -EINVAL; return kvm_sev_es_string_io(&svm->vcpu, size, port, - svm->ghcb_sa, svm->ghcb_sa_len, in); + svm->ghcb_sa, svm->ghcb_sa_len / size, in); } void sev_es_init_vmcb(struct vcpu_svm *svm) --2.27.0
I could be missing something, but I'm pretty sure that this is wrong. The GHCB spec says that `exit_info_2` is the `rep` count. Not the string length. For example, given a `rep outsw` instruction, with `ECX` set to `8`, the rep count written into `SW_EXITINFO2` should be eight x86 words (i.e., 16 bytes) and the IO size should be one x86 word (i.e., 2 bytes). In other words, the code was correct before this patch. This patch is incorrectly dividing the rep count by the IO size, causing the string IO to be truncated.