linux-kernel - Re: [PATCH 7/7] KVM: VMX: Introduce test mode related to EPT violation VE

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Message-ID: <7c0bbec7-fa5c-4f55-9c08-ca0e94e68f7c@redhat.com>
Date: Fri, 17 May 2024 18:35:01 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 Isaku Yamahata <isaku.yamahata@...el.com>
Subject: Re: [PATCH 7/7] KVM: VMX: Introduce test mode related to EPT
 violation VE

On 5/16/24 01:38, Sean Christopherson wrote:
> On Tue, May 07, 2024, Paolo Bonzini wrote:
>> @@ -5200,6 +5215,9 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
>>   	if (is_invalid_opcode(intr_info))
>>   		return handle_ud(vcpu);
>>   
>> +	if (KVM_BUG_ON(is_ve_fault(intr_info), vcpu->kvm))
>> +		return -EIO;
> 
> I've hit this three times now when running KVM-Unit-Tests (I'm pretty sure it's
> the EPT test, unsurprisingly).  And unless I screwed up my testing, I verified it
> still fires with Isaku's fix[*], though I'm suddenly having problems repro'ing.
> 
> I'll update tomorrow as to whether I botched my testing of Isaku's fix, or if
> there's another bug lurking.
> 
> https://lore.kernel.org/all/20240515173209.GD168153@ls.amr.corp.intel.com

I cannot reproduce it on a Skylake (Xeon Gold 5120), with or without 
Isaku's fix, with either ./runtests.sh or your reproducer line.

However I can reproduce it only if eptad=0 and with the following line:

/x86/run x86/vmx.flat -smp 1 -cpu max,host-phys-bits,+vmx -m 2560 \
   -append 'ept_access_test_not_present ept_access_test_read_only'



Paolo