From: Jason Gunthorpe <jgg@nvidia.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Piotr Jaroszynski <pjaroszynski@nvidia.com>,
Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
Alistair Popple <apopple@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>, Zi Yan <ziy@nvidia.com>,
Breno Leitao <leitao@debian.org>,
stable@vger.kernel.org
Subject: Re: [PATCH] arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults
Date: Wed, 4 Mar 2026 09:44:45 -0400 [thread overview]
Message-ID: <20260304134445.GN972761@nvidia.com> (raw)
In-Reply-To: <1080db49-2f83-4fec-ba73-94c6b3a8f7fa@arm.com>
On Wed, Mar 04, 2026 at 12:20:31PM +0000, Ryan Roberts wrote:
> > static int __cont_access_flags_changed(pte_t *ptep, pte_t pte, int ncontig)
> > {
> > + const pteval_t access_mask = PTE_RDONLY | PTE_AF | PTE_WRITE | PTE_DIRTY;
> > + pteval_t pte_access = pte_val(pte) & access_mask;
> > int i;
> >
> > - if (pte_write(pte) != pte_write(__ptep_get(ptep)))
> > - return 1;
> > -
> > for (i = 0; i < ncontig; i++) {
> > - pte_t orig_pte = __ptep_get(ptep + i);
> > -
> > - if (pte_dirty(pte) != pte_dirty(orig_pte))
> > - return 1;
> > -
> > - if (pte_young(pte) != pte_young(orig_pte))
> > + if ((pte_val(__ptep_get(ptep + i)) & access_mask) != pte_access)
> > return 1;
> > }
>
> I think, based on all the above, the current version is actually not buggy. But
> I'm only willing to go to 95% confidence :)
If I understand it right James already found and fixed a case that
violated the invariant right? Maybe it is wise to be robust since
things lock up if it goes wrong.
Jason
next prev parent reply other threads:[~2026-03-04 13:44 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-03 6:37 Piotr Jaroszynski
2026-03-03 7:19 ` James Houghton
2026-03-03 12:45 ` Jason Gunthorpe
2026-03-03 21:40 ` Piotr Jaroszynski
2026-03-03 8:38 ` Ryan Roberts
2026-03-03 18:40 ` Piotr Jaroszynski
2026-03-03 19:12 ` Jason Gunthorpe
2026-03-04 12:20 ` Ryan Roberts
2026-03-04 13:44 ` Jason Gunthorpe [this message]
2026-03-04 11:17 ` Catalin Marinas
2026-03-04 13:43 ` Jason Gunthorpe
2026-03-04 15:01 ` Catalin Marinas
2026-03-04 15:39 ` Jason Gunthorpe
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