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

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Date: Fri, 17 May 2024 09:38:09 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.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 Fri, May 17, 2024, Paolo Bonzini wrote:
> 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'

FWIW, I tried that on RPL, still no failure.