linux-kernel - Re: [PATCH 2/3] mm/tlb: Fix wrong judgement in allocate_global

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Message-ID: <df4f0ce855b7acd6fc9777457b89359e075a5cbb.camel@surriel.com>
Date: Sat, 29 Mar 2025 13:33:44 -0400
From: Rik van Riel <riel@...riel.com>
To: Hou Wenlong <houwenlong.hwl@...group.com>, linux-kernel@...r.kernel.org
Cc: Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski
 <luto@...nel.org>,  Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner
 <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,  Borislav Petkov	
 <bp@...en8.de>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 2/3] mm/tlb: Fix wrong judgement in
 allocate_global_asid()

On Sat, 2025-03-29 at 21:05 +0800, Hou Wenlong wrote:
> In allocate_global_asid(), 'global_asid_available' cannot be zero, as
> it
> has already been checked in use_global_asid(). Therefore, the warning
> in
> allocate_global_asid() cannot be triggered; fix the wrong judgment in
> allocate_global_asid().
> 
> Fixes: d504d1247e36 ("x86/mm: Add global ASID allocation helper
> functions")
> Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>

Good catch.

Reviewed-by: Rik van Riel <riel@...riel.com>

Looking at allocate_global_asid() again, I wonder if
that needs to be turned back into a loop.

What if we have no global asids available, and then
an asid gets freed that is smaller than the value
of last_global_asid?
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