linux-kernel - Re: [PATCH v13 04/14] x86/mm: use INVLPGB for kernel TLB flushes

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Message-ID: <20250224123142.GFZ7xmruuyrc2Wy0r7@fat_crate.local>
Date: Mon, 24 Feb 2025 13:31:42 +0100
From: Borislav Petkov <bp@...en8.de>
To: Rik van Riel <riel@...riel.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, peterz@...radead.org,
	dave.hansen@...ux.intel.com, zhengqi.arch@...edance.com,
	nadav.amit@...il.com, thomas.lendacky@....com, kernel-team@...a.com,
	linux-mm@...ck.org, akpm@...ux-foundation.org, jackmanb@...gle.com,
	jannh@...gle.com, mhklinux@...look.com, andrew.cooper3@...rix.com,
	Manali.Shukla@....com, mingo@...nel.org
Subject: Re: [PATCH v13 04/14] x86/mm: use INVLPGB for kernel TLB flushes

On Sun, Feb 23, 2025 at 02:48:54PM -0500, Rik van Riel wrote:
> Use broadcast TLB invalidation for kernel addresses when available.
> 
> Remove the need to send IPIs for kernel TLB flushes.
> 
> Signed-off-by: Rik van Riel <riel@...riel.com>
> Reviewed-by: Nadav Amit <nadav.amit@...il.com>
> Tested-by: Manali Shukla <Manali.Shukla@....com>
> Tested-by: Brendan Jackman <jackmanb@...gle.com>
> Tested-by: Michael Kelley <mhklinux@...look.com>

What's the point of keeping those Tested-by tags if you still keep changing
the patchset?

> ---
>  arch/x86/mm/tlb.c | 34 ++++++++++++++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index dbcb5c968ff9..59396a3c6e9c 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -1077,6 +1077,20 @@ void flush_tlb_all(void)
>  	on_each_cpu(do_flush_tlb_all, NULL, 1);
>  }
>  
> +static bool invlpgb_kernel_range_flush(struct flush_tlb_info *info)
> +{
> +	unsigned long addr;
> +	unsigned long nr;

Oh, c'mon:

	unsigned long addr, nr;

> +
> +	for (addr = info->start; addr < info->end; addr += nr << PAGE_SHIFT) {
> +		nr = (info->end - addr) >> PAGE_SHIFT;
> +		nr = clamp_val(nr, 1, invlpgb_count_max);
> +		invlpgb_flush_addr_nosync(addr, nr);
> +	}
> +	__tlbsync();
> +	return true;

Unused retval - that function looks like it wants to be void.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette