linux-kernel - Re: [PATCH v2 0/3] skip redundant TLB sync IPIs

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Message-ID: <f920487a-632c-407b-b092-7de87f66f4bb@intel.com>
Date: Sat, 3 Jan 2026 09:06:30 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Lance Yang <lance.yang@...ux.dev>,
 "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: will@...nel.org, aneesh.kumar@...nel.org, npiggin@...il.com,
 peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, arnd@...db.de,
 lorenzo.stoakes@...cle.com, ziy@...dia.com, baolin.wang@...ux.alibaba.com,
 Liam.Howlett@...cle.com, npache@...hat.com, ryan.roberts@....com,
 dev.jain@....com, baohua@...nel.org, ioworker0@...il.com,
 shy828301@...il.com, riel@...riel.com, jannh@...gle.com,
 linux-arch@...r.kernel.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH v2 0/3] skip redundant TLB sync IPIs

On 1/3/26 00:39, Lance Yang wrote:
...
> Maybe we could do that as a follow-up. I'd like to keep things simple
> for now, so we just add a bool property to skip redundant TLB sync IPIs
> on systems without INVLPGB support.

It's not just INVLPGB support. Take a look at hyperv_flush_tlb_multi(),
for instance. It can eventually land back in native_flush_tlb_multi(),
but would also "fail" the pv_ops check in all cases.

It's not that Hyper-V performance is super important, it just that the
semantics of the chosen approach here are rather complicated.

> Then we could add the mm->context (or something similar) tracking later
> to handle things more precisely.
> 
> Anyway, I'm open to going straight to the mm->context approach as well
> and happy to do that instead :D

I'd really like to see what an mm->context approach looks like before we
go forward with what is being proposed here.

Is there some kind of hurry to get this done immediately?