linux-kernel - Re: [PATCH v5] KVM: selftests: Test READ=>WRITE dirty logging behavior for shadow MMU

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Message-ID: <aWl8cyfgqdbOrMV1@google.com>
Date: Thu, 15 Jan 2026 15:46:59 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] KVM: selftests: Test READ=>WRITE dirty logging
 behavior for shadow MMU

On Thu, Jan 15, 2026, Yosry Ahmed wrote:
> On Thu, Jan 15, 2026 at 09:21:54AM -0800, Sean Christopherson wrote:
> > +static void l2_guest_code(vm_vaddr_t base)
> >  {
> > -	READ_ONCE(*a);
> > -	WRITE_ONCE(*a, 1);
> > -	GUEST_SYNC(true);
> > -	GUEST_SYNC(false);
> > +	vm_vaddr_t page0 = TEST_GUEST_ADDR(base, 0);
> > +	vm_vaddr_t page1 = TEST_GUEST_ADDR(base, 1);
> >  
> > -	WRITE_ONCE(*b, 1);
> > -	GUEST_SYNC(true);
> > -	WRITE_ONCE(*b, 1);
> > -	GUEST_SYNC(true);
> > -	GUEST_SYNC(false);
> > +	READ_ONCE(*(u64 *)page0);
> > +	GUEST_SYNC(page0 | TEST_SYNC_READ_FAULT);
> > +	WRITE_ONCE(*(u64 *)page0, 1);
> > +	GUEST_SYNC(page0 | TEST_SYNC_WRITE_FAULT);
> > +	READ_ONCE(*(u64 *)page0);
> > +	GUEST_SYNC(page0 | TEST_SYNC_NO_FAULT);
> > +
> > +	WRITE_ONCE(*(u64 *)page1, 1);
> > +	GUEST_SYNC(page1 | TEST_SYNC_WRITE_FAULT);
> > +	WRITE_ONCE(*(u64 *)page1, 1);
> > +	GUEST_SYNC(page1 | TEST_SYNC_WRITE_FAULT);
> > +	READ_ONCE(*(u64 *)page1);
> > +	GUEST_SYNC(page1 | TEST_SYNC_NO_FAULT);
> > +	GUEST_SYNC(page1 | TEST_SYNC_NO_FAULT);
> 
> Extra GUEST_SYNC()?

Yeah, I'm guessing it was a copy+paste goof, I can't think of any value added by
a second sync here.  I'll drop it when applying.

Thanks!