[edk2-devel] [RFC/RFT PATCH] OvmfPkg/IoMmuDxe: don't rely on TPLs for re-entrancy

[Gerd Hoffmann]

On Wed, Aug 23, 2023 at 05:11:49PM +0200, Ard Biesheuvel wrote:
> On Wed, 23 Aug 2023 at 13:08, Gerd Hoffmann <kraxel at redhat.com> wrote:
> >
> > On Tue, Aug 22, 2023 at 09:57:12AM +0200, Ard Biesheuvel wrote:
> > > On Tue, 22 Aug 2023 at 08:25, Gerd Hoffmann <kraxel at redhat.com> wrote:
> > > >
> > > > Looks good to me.
> > > >
> > > > What is the status?  Merged?  Or waiting for testing still?  If so I can
> > > > create a test build with the patch and ask our QE department to check
> > > > it.
> > > >
> > >
> > > Still waiting for testing, so yes, please test.
> >
> > Hmm, QE reports back it slows down the boot alot.  No boot hangs yet
> > with 12 test runs so far, which isn't that much for a reproduce rate
> > below 20% ...
> >
> > https://bugzilla.redhat.com//show_bug.cgi?id=2211060#c28
> >
> > So I guess we go with the TPL version for the coming stable tag and
> > leave any improvements for later ...
> >
> 
> Yeah, this was not going to make the stable tag in any case.
> 
> The boot speed regression seems odd, though - this is effectively UP
> code so there shouldn't be any contention, the only thing this patch
> does is ensure that the critical section is restarted if it was
> interrupted
> 
> Are we comparing apples with apples here?

Hoping for an answer tomorrow, asked QE folks the same thing in comment
30.  The first test build (comment 11) essentially is stable-2023-05 with
a52044a9e602 ("OvmfPkg/IoMmuDxe: add locking to
IoMmuAllocateBounceBuffer") cherry-picked, the second test build
(comment 27) is stable-2023-05 + a52044a9e602 + this patch.

take care,
  Gerd



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