linux-kernel - Re: [BUG] x86/mm: regression after 4a02ed8e1cc3

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Message-Id: <3990BE94-FB14-4D33-BEC3-07EB487A2490@gmail.com>
Date: Tue, 2 Sep 2025 19:08:08 +0300
From: Nadav Amit <nadav.amit@...il.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
 Rik van Riel <riel@...riel.com>,
 the arch/x86 maintainers <x86@...nel.org>,
 Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 Borislav Petkov <bp@...en8.de>,
 peterz@...radead.org,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 zhengqi.arch@...edance.com,
 thomas.lendacky@....com,
 kernel-team@...a.com,
 "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 jackmanb@...gle.com,
 jannh@...gle.com,
 mhklinux@...look.com,
 andrew.cooper3@...rix.com,
 Manali.Shukla@....com,
 Ingo Molnar <mingo@...nel.org>,
 baolu.lu@...el.com,
 david.guckian@...el.com,
 damian.muszynski@...el.com
Subject: Re: [BUG] x86/mm: regression after 4a02ed8e1cc3



> On 2 Sep 2025, at 18:50, Dave Hansen <dave.hansen@...el.com> wrote:
> 
> On 9/2/25 08:44, Giovanni Cabiddu wrote:
>> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
>> index 39f80111e6f1..e66c7662c254 100644
>> --- a/arch/x86/mm/tlb.c
>> +++ b/arch/x86/mm/tlb.c
>> @@ -1459,7 +1459,7 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
>> 
>> 	put_flush_tlb_info();
>> 	put_cpu();
>> - 	mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);
>> + 	mmu_notifier_arch_invalidate_secondary_tlbs(mm, info->start, info->end);
>> }
> 
> That does look like the right solution.
> 
> This is the downside of wrapping everything up in that 'info' struct;
> it's not obvious that the canonical source of the start/end information
> moved from those variables into the structure.

Just a reminder (which I am sure that you know): the main motivation behind
this info struct is to allow the payload that is required for the TLB
shootdown to be in a single cache-line.

It would be nice (if possible) that callees like broadcast_tlb_flush()
would constify flush_tlb_info (I’m not encouraging lots of consification,
but maybe it’s appropriate here) to prevent the misuse of flush_tlb_info.