linux-kernel - Re: [PATCH v5 10/12] x86,tlb: do targeted broadcast flushing from tlbbatch code

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Message-ID: <2c93b3f17e658483e3ea03ca3f0a717668fd117d.camel@surriel.com>
Date: Mon, 20 Jan 2025 11:11:10 -0500
From: Rik van Riel <riel@...riel.com>
To: Nadav Amit <nadav.amit@...il.com>, x86@...nel.org
Cc: linux-kernel@...r.kernel.org, bp@...en8.de, peterz@...radead.org, 
	dave.hansen@...ux.intel.com, zhengqi.arch@...edance.com,
 thomas.lendacky@....com, 	kernel-team@...a.com, linux-mm@...ck.org,
 akpm@...ux-foundation.org, 	jannh@...gle.com, mhklinux@...look.com,
 andrew.cooper3@...rix.com
Subject: Re: [PATCH v5 10/12] x86,tlb: do targeted broadcast flushing from
 tlbbatch code

On Mon, 2025-01-20 at 16:14 +0200, Nadav Amit wrote:
> 
> I am not sure we are on the same page. What I suggested is:
> 
> 1. arch_tlbbatch_flush() would still do tlbsync()
> 2. No migrate_enable() in arch_tlbbatch_flush()
> 3. No migrate_disable() in arch_tlbbatch_add_pending()
> 4. arch_tlbbatch_add_pending() sets
> cpu_tlbstate.pending_tlb_broadcast
> 5. switch_mm_irqs_off() checks cpu_tlbstate.pending_tlb_broadcast and
> if 
> it is set performs tlbsync and clears it.
> 
How does that synchronize the page freeing (from page
reclaim) with the TLBSYNCs?

What guarantees that the page reclaim path won't free
the pages until after TLBSYNC has completed on the CPUs
that kicked off asynchronous flushes with INVPLGB?

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