lkml.org 
[lkml]   [2020]   [Sep]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC PATCH 09/35] KVM: SVM: Do not emulate MMIO under SEV-ES
From
Date
On 9/14/20 4:33 PM, Sean Christopherson wrote:
> On Mon, Sep 14, 2020 at 03:15:23PM -0500, Tom Lendacky wrote:
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>
>> When a guest is running as an SEV-ES guest, it is not possible to emulate
>> MMIO. Add support to prevent trying to perform MMIO emulation.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>> arch/x86/kvm/mmu/mmu.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
>> index a5d0207e7189..2e1b8b876286 100644
>> --- a/arch/x86/kvm/mmu/mmu.c
>> +++ b/arch/x86/kvm/mmu/mmu.c
>> @@ -5485,6 +5485,13 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,
>> if (!mmio_info_in_cache(vcpu, cr2_or_gpa, direct) && !is_guest_mode(vcpu))
>> emulation_type |= EMULTYPE_ALLOW_RETRY_PF;
>> emulate:
>> + /*
>> + * When the guest is an SEV-ES guest, emulation is not possible. Allow
>> + * the guest to handle the MMIO emulation.
>> + */
>> + if (vcpu->arch.vmsa_encrypted)
>> + return 1;
>
> A better approach is to refactor need_emulation_on_page_fault() (the hook
> that's just out of sight in this patch) into a more generic
> kvm_x86_ops.is_emulatable() so that the latter can be used to kill emulation
> everywhere, and for other reasons. E.g. TDX obviously shares very similar
> logic, but SGX also adds a case where KVM can theoretically end up in an
> emulator path without the ability to access the necessary guest state.
>
> I have exactly such a prep patch (because SGX and TDX...), I'll get it posted
> in the next day or two.

Sounds good. I'll check it out when it's posted.

Thanks,
Tom

>
>> +
>> /*
>> * 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
>> --
>> 2.28.0
>>

\
 
 \ /
  Last update: 2020-09-15 17:57    [W:0.105 / U:1.804 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site