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From: Thomas Gleixner <tglx@kernel.org>
To: David Stevens <stevensd@google.com>, Pasha Tatashin
 <pasha.tatashin@soleen.com>, Linus Walleij <linus.walleij@linaro.org>,
 Will Deacon <willdeacon@google.com>, Quentin Perret <qperret@google.com>,
 Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Dave
 Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, "H. Peter Anvin"
 <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>, Xin Li
 <xin@zytor.com>, Peter Zijlstra <peterz@infradead.org>, Andrew Morton
 <akpm@linux-foundation.org>, David Hildenbrand <david@kernel.org>, Lorenzo
 Stoakes <ljs@kernel.org>, "Liam R. Howlett" <Liam.Howlett@oracle.com>,
 Vlastimil Babka <vbabka@kernel.org>, Mike Rapoport <rppt@kernel.org>,
 Suren Baghdasaryan <surenb@google.com>, Michal Hocko <mhocko@suse.com>,
 Uladzislau Rezki <urezki@gmail.com>, Kees Cook <kees@kernel.org>
Cc: David Stevens <stevensd@google.com>, linux-kernel@vger.kernel.org,
 linux-mm@kvack.org
Subject: Re: [PATCH v2 10/13] fork: Store task pointer in unpopulated stack
 ptes
In-Reply-To: <20260424191456.2679717-11-stevensd@google.com>
References: <20260424191456.2679717-1-stevensd@google.com>
 <20260424191456.2679717-11-stevensd@google.com>
Date: Sat, 27 Jun 2026 00:46:35 +0200
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On Fri, Apr 24 2026 at 12:14, David Stevens wrote:
> Store the task pointer in the ptes of the unpopulated pages of dynamic
> stacks, to allow the vm_struct pointer to be retrieved without relying
> on any locks or current.

You fail to explain why you can't use current. Changelogs have to
describe the WHY and not the WHAT.

>  
> -bool is_vmalloc_addr(const void *x)
> +noinstr bool is_vmalloc_addr(const void *x)
>  {
>  	unsigned long addr = (unsigned long)kasan_reset_tag(x);

noinstr is not enough here unless this depends on !KASAN because
kasan_reset_tag() is a 'static inline' which CLANG happily puts out of
line into the instrumentable section...