From: "Jose A. Perez de Azpillaga" <azpijr@gmail.com>
To: Kiryl Shutsemau <kirill@shutemov.name>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
"David Hildenbrand (Arm)" <david@kernel.org>
Cc: "Kiryl Shutsemau (Meta)" <kas@kernel.org>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Peter Xu <peterx@redhat.com>, Lorenzo Stoakes <ljs@kernel.org>,
"Liam R. Howlett" <liam@infradead.org>,
Vlastimil Babka <vbabka@kernel.org>,
"Mike Rapoport (Microsoft)" <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>, Zi Yan <ziy@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Nico Pache <nico.pache@linux.dev>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>, Lance Yang <lance.yang@linux.dev>,
Usama Arif <usama.arif@linux.dev>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Andrew Donnellan <andrew+kernel@donnellan.id.au>,
Rohan McLure <rmclure@linux.ibm.com>, Tejun Heo <tj@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com
Subject: Re: [PATCH v2] x86/mm: Remove the zapped-entry checks
Date: Thu, 5 Nov 2026 23:09:24 +0100 [thread overview]
Message-ID: <9e98a961-fb45-4e61-a08b-d8d7f8e9894b@gmail.com> (raw)
In-Reply-To: <20261105120322.3319301-1-kirill@shutemov.name>
On 11/5/26 1:03 PM, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
>
> Zapping a range calls arch_check_zapped_pte() for every batch of PTEs,
> which is every page for small folios, and arch_check_zapped_pmd() or
> arch_check_zapped_pud() for every huge leaf. Only x86 implements them, as
> out-of-line functions that warn about a shadow stack entry (Write=0,
> Dirty=1) in a VMA without VM_SHADOW_STACK.
>
> The warning is a VM_WARN_ON_ONCE(), so without CONFIG_DEBUG_VM the
> functions are empty, but the calls remain. With the SRSO "Safe RET"
> mitigation the return of every such call mispredicts.
>
> The x86 helpers already keep such entries out of other VMAs.
> pte_wrprotect(), pte_mkdirty(), pte_modify() and their PMD versions go
> through SavedDirty, and only pte_mkwrite() and pmd_mkwrite() on a
> VM_SHADOW_STACK VMA create the combination.
makes sense to me.
Reviewed-by: Jose A. Perez de Azpillaga <azpijr@gmail.com>
--
cheers,
jose a. p-a
prev parent reply other threads:[~2026-11-05 22:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-05 12:03 Kiryl Shutsemau
2026-11-05 22:09 ` Jose A. Perez de Azpillaga [this message]
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