linux-kernel - Re: [PATCH v4 29/30] x86/mm, mm/vmalloc: Defer flush_tlb_kernel_range() targeting NOHZ

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: <CAG48ez2bSh6=J8cXJhqYX=Y8pXcGsFgC05HsGcF0b1sJK2VH7A@mail.gmail.com>
Date: Tue, 25 Mar 2025 19:41:49 +0100
From: Jann Horn <jannh@...gle.com>
To: Valentin Schneider <vschneid@...hat.com>, Rik van Riel <riel@...riel.com>
Cc: Dave Hansen <dave.hansen@...el.com>, linux-kernel@...r.kernel.org, x86@...nel.org, 
	virtualization@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	loongarch@...ts.linux.dev, linux-riscv@...ts.infradead.org, 
	linux-perf-users@...r.kernel.org, xen-devel@...ts.xenproject.org, 
	kvm@...r.kernel.org, linux-arch@...r.kernel.org, rcu@...r.kernel.org, 
	linux-hardening@...r.kernel.org, linux-mm@...ck.org, 
	linux-kselftest@...r.kernel.org, bpf@...r.kernel.org, 
	bcm-kernel-feedback-list@...adcom.com, Juergen Gross <jgross@...e.com>, 
	Ajay Kaher <ajay.kaher@...adcom.com>, Alexey Makhalov <alexey.amakhalov@...adcom.com>, 
	Russell King <linux@...linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Peter Zijlstra <peterz@...radead.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, 
	Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	"Liang, Kan" <kan.liang@...ux.intel.com>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Frederic Weisbecker <frederic@...nel.org>, "Paul E. McKenney" <paulmck@...nel.org>, 
	Jason Baron <jbaron@...mai.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Ard Biesheuvel <ardb@...nel.org>, Neeraj Upadhyay <neeraj.upadhyay@...nel.org>, 
	Joel Fernandes <joel@...lfernandes.org>, Josh Triplett <josh@...htriplett.org>, 
	Boqun Feng <boqun.feng@...il.com>, Uladzislau Rezki <urezki@...il.com>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Lai Jiangshan <jiangshanlai@...il.com>, 
	Zqiang <qiang.zhang1211@...il.com>, Juri Lelli <juri.lelli@...hat.com>, 
	Clark Williams <williams@...hat.com>, Yair Podemsky <ypodemsk@...hat.com>, 
	Tomas Glozar <tglozar@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Ben Segall <bsegall@...gle.com>, 
	Mel Gorman <mgorman@...e.de>, Kees Cook <kees@...nel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Christoph Hellwig <hch@...radead.org>, 
	Shuah Khan <shuah@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Miguel Ojeda <ojeda@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	"Mike Rapoport (Microsoft)" <rppt@...nel.org>, Samuel Holland <samuel.holland@...ive.com>, Rong Xu <xur@...gle.com>, 
	Nicolas Saenz Julienne <nsaenzju@...hat.com>, Geert Uytterhoeven <geert@...ux-m68k.org>, 
	Yosry Ahmed <yosryahmed@...gle.com>, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, 
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Jinghao Jia <jinghao7@...inois.edu>, 
	Luis Chamberlain <mcgrof@...nel.org>, Randy Dunlap <rdunlap@...radead.org>, 
	Tiezhu Yang <yangtiezhu@...ngson.cn>
Subject: Re: [PATCH v4 29/30] x86/mm, mm/vmalloc: Defer flush_tlb_kernel_range()
 targeting NOHZ_FULL CPUs

On Tue, Mar 25, 2025 at 6:52 PM Valentin Schneider <vschneid@...hat.com> wrote:
> On 20/02/25 09:38, Dave Hansen wrote:
> > But, honestly, I'm still not sure this is worth all the trouble. If
> > folks want to avoid IPIs for TLB flushes, there are hardware features
> > that *DO* that. Just get new hardware instead of adding this complicated
> > pile of software that we have to maintain forever. In 10 years, we'll
> > still have this software *and* 95% of our hardware has the hardware
> > feature too.
>
> Sorry, you're going to have to deal with my ignorance a little bit longer...
>
> Were you thinking x86 hardware specifically, or something else?
> AIUI things like arm64's TLBIVMALLE1IS can do what is required without any
> IPI:
>
> C5.5.78
> """
> The invalidation applies to all PEs in the same Inner Shareable shareability domain as the PE that
> executes this System instruction.
> """
>
> But for (at least) these architectures:
>
>   alpha
>   x86
>   loongarch
>   mips
>   (non-freescale 8xx) powerpc
>   riscv
>   xtensa
>
> flush_tlb_kernel_range() has a path with a hardcoded use of on_each_cpu(),
> so AFAICT for these the IPIs will be sent no matter the hardware.

On X86, both AMD and Intel have some fairly recently introduced CPU
features that can shoot down TLBs remotely.

The patch series
<https://lore.kernel.org/all/20250226030129.530345-1-riel@surriel.com/>
adds support for the AMD flavor; that series landed in the current
merge window (it's present in the mainline git repository now and should
be part of 6.15). I think support for the Intel flavor has not yet
been implemented, but the linked patch series mentions a plan to look
at the Intel flavor next.