From: Jim Mattson <jmattson@google.com>
To: Brijesh Singh <brijesh.singh@amd.com>
Cc: "kvm list" <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
"Borislav Petkov" <bp@alien8.de>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Joerg Roedel" <joro@8bytes.org>, "Borislav Petkov" <bp@suse.de>,
"Tom Lendacky" <thomas.lendacky@amd.com>
Subject: Re: [Part2 PATCH v9 38/38] KVM: X86: Restart the guest when insn_len is zero and SEV is enabled
Date: Fri, 1 Feb 2019 12:21:18 -0800 [thread overview]
Message-ID: <CALMp9eTpMm4qpNCUj00qk8CA7BmW-uq4YRwHzKa_GAwON2kgyQ@mail.gmail.com> (raw)
In-Reply-To: <20171205010616.5958-9-brijesh.singh@amd.com>
On Mon, Dec 4, 2017 at 5:07 PM Brijesh Singh <brijesh.singh@amd.com> wrote:
>
> On AMD platforms, under certain conditions insn_len may be zero on #NPF.
> This can happen if a guest gets a page-fault on data access but the HW
> table walker is not able to read the instruction page (e.g instruction
> page is not present in memory).
>
> Typically, when insn_len is zero, x86_emulate_instruction() walks the
> guest page table and fetches the instruction bytes from guest memory.
> When SEV is enabled, the guest memory is encrypted with guest-specific
> key hence hypervisor will not able to fetch the instruction bytes.
> In those cases we simply restart the guest.
>
> I have encountered this issue when running kernbench inside the guest.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: x86@kernel.org
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> arch/x86/kvm/mmu.c | 10 ++++++++++
> arch/x86/kvm/svm.c | 6 ++++--
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index e5e66e5c6640..d5e5dbd0e5ad 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -4950,6 +4950,16 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
> if (mmio_info_in_cache(vcpu, cr2, direct))
> emulation_type = 0;
> emulate:
> + /*
> + * On AMD platforms, under certain conditions insn_len may be zero on #NPF.
> + * This can happen if a guest gets a page-fault on data access but the HW
> + * table walker is not able to read the instruction page (e.g instruction
> + * page is not present in memory). In those cases we simply restart the
> + * guest.
> + */
> + if (unlikely(insn && !insn_len))
> + return 1;
> +
How does this work, for instance, with MMIO at CPL3 with SMAP enabled?
next prev parent reply other threads:[~2019-02-01 20:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-05 1:06 [Part2 PATCH v9 30/38] KVM: SVM: Add support for SEV LAUNCH_FINISH command Brijesh Singh
2017-12-05 1:06 ` [Part2 PATCH v9 31/38] KVM: SVM: Add support for SEV GUEST_STATUS command Brijesh Singh
2017-12-05 1:06 ` [Part2 PATCH v9 32/38] KVM: SVM: Add support for SEV DEBUG_DECRYPT command Brijesh Singh
2017-12-05 1:06 ` [Part2 PATCH v9 33/38] KVM: SVM: Add support for SEV DEBUG_ENCRYPT command Brijesh Singh
2017-12-05 1:06 ` [Part2 PATCH v9 34/38] KVM: SVM: Add support for SEV LAUNCH_SECRET command Brijesh Singh
2017-12-05 1:06 ` [Part2 PATCH v9 35/38] KVM: SVM: Pin guest memory when SEV is active Brijesh Singh
2017-12-05 1:06 ` [Part2 PATCH v9 36/38] KVM: SVM: Clear C-bit from the page fault address Brijesh Singh
2017-12-05 1:06 ` [Part2 PATCH v9 37/38] KVM: SVM: Do not install #UD intercept when SEV is enabled Brijesh Singh
2017-12-05 1:06 ` [Part2 PATCH v9 38/38] KVM: X86: Restart the guest when insn_len is zero and " Brijesh Singh
2019-02-01 20:21 ` Jim Mattson [this message]
2019-02-04 19:22 ` Singh, Brijesh
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