linux-kernel - Re: [PATCH 06/12] x86/mm: use INVLPGB for kernel TLB flushes

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <f3fee10b851f21866cc6ba8a4391705999bb4f53.camel@surriel.com>
Date: Fri, 10 Jan 2025 15:29:16 -0500
From: Rik van Riel <riel@...riel.com>
To: Tom Lendacky <thomas.lendacky@....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 06/12] x86/mm: use INVLPGB for kernel TLB flushes

On Fri, 2025-01-10 at 12:53 -0600, Tom Lendacky wrote:
> On 12/30/24 11:53, Rik van Riel wrote:
> > Use broadcast TLB invalidation for kernel addresses when available.
> > 
> > +static void broadcast_kernel_range_flush(unsigned long start,
> > unsigned long end)
> > +{
> > +	unsigned long addr;
> > +	unsigned long maxnr = invlpgb_count_max;
> > +	unsigned long threshold = tlb_single_page_flush_ceiling *
> > maxnr;
> > +
> > +	/*
> > +	 * TLBSYNC only waits for flushes originating on the same
> > CPU.
> > +	 * Disabling migration allows us to wait on all flushes.
> > +	 */
> > +	guard(preempt)();
> > +
> > +	if (end == TLB_FLUSH_ALL ||
> > +	    (end - start) > threshold << PAGE_SHIFT) {
> > +		invlpgb_flush_all();
> > +	} else {
> > +		unsigned long nr;
> > +		for (addr = start; addr < end; addr += nr <<
> > PAGE_SHIFT) {
> > +			nr = min((end - addr) >> PAGE_SHIFT,
> > maxnr);
> > +			invlpgb_flush_addr(addr, nr);
> > +		}
> 
> Would it be better to put this loop in the actual invlpgb_flush*
> function(s)? Then callers don't have to worry about it, similar to
> what is
> done in clflush_cache_range() / clflush_cache_range_opt().

Maybe?

We only have one caller, though.


-- 
All Rights Reversed.