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

[Paolo Bonzini]

On 5/17/24 18:38, Sean Christopherson wrote:
> > > 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@xxxxxxxxxxxxxxxxxxxxx
> > 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.

Ok, so it does look like a CPU issue.  Even with the fixes you 
identified, I don't see any other solution than adding scary text in 
Kconfig, defaulting it to "n", and adding an also-very-scary 
pr_err_once("...") the first time VMPTRLD is executed with 
CONFIG_KVM_INTEL_PROVE_VE.

Paolo