linux-kernel - Re: [PATCH 07/12] x86/tlb: use INVLPGB in flush_tlb

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Message-ID: <194072ff-32af-4a5d-8e73-0a45f75290e7@intel.com>
Date: Mon, 6 Jan 2025 09:29:33 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Rik van Riel <riel@...riel.com>, x86@...nel.org
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com,
 dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
 tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
 akpm@...ux-foundation.org, nadav.amit@...il.com, zhengqi.arch@...edance.com,
 linux-mm@...ck.org
Subject: Re: [PATCH 07/12] x86/tlb: use INVLPGB in flush_tlb_all

On 12/30/24 09:53, Rik van Riel wrote:
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -1074,6 +1074,12 @@ static void do_flush_tlb_all(void *info)
>  void flush_tlb_all(void)
>  {
>  	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
> +	if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) {
> +		guard(preempt)();
> +		invlpgb_flush_all();
> +		tlbsync();
> +		return;
> +	}

After seeing a few of these, I'd really prefer that the preempt and
tlbsync() logic be hidden in the invlpgb_*() helper, or *a* helper at least.

This would be a lot easier on the eyes if it were something like:

	flushed = invlpgb_flush_all();
	if (flushed)
		return;

or even:

	if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) {
		invlpgb_flush_all();
		return;
	}