linux-kernel - Re: [PATCH v11 03/12] x86/mm: consolidate full flush threshold decision

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250219112122.GLZ7W-sjOTi-LXlRp4@fat_crate.local>
Date: Wed, 19 Feb 2025 12:21:22 +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,
	Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH v11 03/12] x86/mm: consolidate full flush threshold
 decision

On Thu, Feb 13, 2025 at 11:13:54AM -0500, Rik van Riel wrote:
> @@ -1009,6 +1009,15 @@ static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
>  	info->initiating_cpu	= smp_processor_id();
>  	info->trim_cpumask	= 0;
>  
> +	/*
> +	 * If the number of flushes is so large that a full flush
> +	 * would be faster, do a full flush.
> +	 */
> +	if ((end - start) >> stride_shift > tlb_single_page_flush_ceiling) {
> +		info->start = 0;
> +		info->end = TLB_FLUSH_ALL;
> +	}

And if you move the range decision before the info-> struct members
assignment, it becomes even more readable because you're using start and end
in the check and then you assign it so a reader doesn't have to go and look
whether start and end are the same as info->start and info->end:

        /*
         * If the number of flushes is so large that a full flush
         * would be faster, do a full flush.
         */
        if ((end - start) >> stride_shift > tlb_single_page_flush_ceiling) {
                start = 0;
                end = TLB_FLUSH_ALL;
        }

        info->start             = start;
        info->end               = end;
        info->mm                = mm;
        info->stride_shift      = stride_shift;
        info->freed_tables      = freed_tables;
        info->new_tlb_gen       = new_tlb_gen;
        info->initiating_cpu    = smp_processor_id();
        info->trim_cpumask      = 0;

        return info;
}

with that:

Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>

-- 
Regards/Gruss,
    Boris.

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