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From: Oliver Upton <oliver.upton@linux.dev>
To: Ricardo Koller <ricarkol@google.com>
Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, andrew.jones@linux.dev,
	pbonzini@redhat.com, maz@kernel.org, alexandru.elisei@arm.com,
	eric.auger@redhat.com, yuzenghui@huawei.com
Subject: Re: [PATCH 1/4] KVM: selftests: aarch64: Relax userfaultfd read vs.
 write checks
Message-ID: <Y9AmGHMjx6BZX0gy@google.com>
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 <Y88TLcuetXMSYyfD@google.com>
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Ricardo,

On Tue, Jan 24, 2023 at 08:17:49AM -0800, Ricardo Koller wrote:
> On Mon, Jan 23, 2023 at 11:07:25PM +0000, Oliver Upton wrote:
> > On Tue, Jan 10, 2023 at 02:24:29AM +0000, Ricardo Koller wrote:
> > > Only Stage1 Page table walks (S1PTW) writing a PTE on an unmapped page
> > > should result in a userfaultfd write. However, the userfaultfd tests in
> > > page_fault_test wrongly assert that any S1PTW is a PTE write.
> > > 
> > > Fix this by relaxing the read vs. write checks in all userfaultfd handlers.
> > > Note that this is also an attempt to focus less on KVM (and userfaultfd)
> > > behavior, and more on architectural behavior. Also note that after commit
> > > "KVM: arm64: Fix S1PTW handling on RO memslots" the userfaultfd fault
> > > (S1PTW with AF on an unmaped PTE page) is actually a read: the translation
> > > fault that comes before the permission fault.
> > 
> > I certainly agree that we cannot make assertions about read v. write
> > when registering uffd in 'missing' mode. We probably need another test
> > to assert that we get write faults for hardware AF updates when using
> > uffd in write protect mode.
> 
> I can do that. Only question, do you prefer having them in this series
> with fixes, or another one?

Oh, don't worry about it for this series as I'd like to grab it sooner
rather than later. Just making a note of some additional improvements to
the test :)

--
Thanks,
Oliver