Re: [PATCH 1/4] KVM: selftests: aarch64: Relax userfaultfd read vs. write checks

[Ricardo Koller <ricarkol@google.com>]

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?

> 
> --
> Thanks,
> Oliver