linux-kernel - Re: [RFC PATCH 20/35] KVM: SVM: Add SEV/SEV-ES support for intercepting INVD

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Date:   Tue, 15 Sep 2020 10:08:56 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [RFC PATCH 20/35] KVM: SVM: Add SEV/SEV-ES support for
 intercepting INVD

On 9/14/20 5:00 PM, Sean Christopherson wrote:
> On Mon, Sep 14, 2020 at 03:15:34PM -0500, Tom Lendacky wrote:
>> From: Tom Lendacky <thomas.lendacky@....com>
>>
>> The INVD instruction intercept performs emulation. Emulation can't be done
>> on an SEV or SEV-ES guest because the guest memory is encrypted.
>>
>> Provide a specific intercept routine for the INVD intercept. Within this
>> intercept routine, skip the instruction for an SEV or SEV-ES guest since
>> it is emulated as a NOP anyway.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>>  arch/x86/kvm/svm/svm.c | 13 ++++++++++++-
>>  1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
>> index 37c98e85aa62..ac64a5b128b2 100644
>> --- a/arch/x86/kvm/svm/svm.c
>> +++ b/arch/x86/kvm/svm/svm.c
>> @@ -2275,6 +2275,17 @@ static int iret_interception(struct vcpu_svm *svm)
>>  	return 1;
>>  }
>>  
>> +static int invd_interception(struct vcpu_svm *svm)
>> +{
>> +	/*
>> +	 * Can't do emulation on any type of SEV guest and INVD is emulated
>> +	 * as a NOP, so just skip it.
>> +	 */
>> +	return (sev_guest(svm->vcpu.kvm))
> 
> Should this be a standalone/backported fix for SEV?

Yes. Let me split it out and send it separately.

Thanks,
Tom

> 
>> +		? kvm_skip_emulated_instruction(&svm->vcpu)
>> +		: kvm_emulate_instruction(&svm->vcpu, 0);
>> +}
>> +
>>  static int invlpg_interception(struct vcpu_svm *svm)
>>  {
>>  	if (!static_cpu_has(X86_FEATURE_DECODEASSISTS))
>> @@ -2912,7 +2923,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
>>  	[SVM_EXIT_RDPMC]			= rdpmc_interception,
>>  	[SVM_EXIT_CPUID]			= cpuid_interception,
>>  	[SVM_EXIT_IRET]                         = iret_interception,
>> -	[SVM_EXIT_INVD]                         = emulate_on_interception,
>> +	[SVM_EXIT_INVD]                         = invd_interception,
>>  	[SVM_EXIT_PAUSE]			= pause_interception,
>>  	[SVM_EXIT_HLT]				= halt_interception,
>>  	[SVM_EXIT_INVLPG]			= invlpg_interception,
>> -- 
>> 2.28.0
>>