Re: Potential bug in soft-dirty bits (with test case)

[Mohamed Alzayat <alzayat@mpi-sws.org>]

Thanks a lot Vlastimil, and Peter for the pointers! Many thanks Will
for actually fixing it (v5.12)!

Thanks,
Mohamed

On Mon, Nov 30, 2020 at 1:50 PM Will Deacon <will@kernel.org> wrote:
>
> On Mon, Nov 30, 2020 at 01:02:41PM +0100, Peter Zijlstra wrote:
> > On Mon, Nov 30, 2020 at 12:51:59PM +0100, Vlastimil Babka wrote:
> > > On 11/30/20 11:37 AM, Mohamed Alzayat wrote:
> >
> > > > Thanks for confirming, Vlastimil!
> > > >
> > > > The first bad commit is: 0758cd8304942292e95a0f750c374533db378b32
> > > > asm-generic/tlb: avoid potential double flush
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0758cd8304942292e95a0f750c374533db378b32
> > > >
> > > > Reverting this commit solves the problem, but this might not be the
> > > > right way of fixing it.
> > >
> > > Thanks for bisecting! Let's CC people involved in that commit. All important
> > > should be in the quoted conversation above.
> >
> > There's a thread about it here:
> >
> >   https://lkml.kernel.org/r/20201120143557.6715-1-will@kernel.org
> >
> > That softdirty code really shouldn't be using mmu_gather imo, but I'm
> > still not clear on what exactly is broken why there.
>
> I'll spin a v2 of that series soon, so I'll add folks here to cc. The
> fact that a test noticed the missing invalidation is a pretty good reason
> for us to add it back!

Thanks, everyone! I appreciate your helpful comments and pointers,
looking forward to the v2 of that series. Until then, reverting to
double TLB flush works fine on recent kernels (tested on v5.10-rc5).

Thanks,
Mohamed

>
> Will
>