From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3EF3ECCD183 for ; Tue, 14 Oct 2025 00:01:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 839348E00B5; Mon, 13 Oct 2025 20:01:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7EA208E0024; Mon, 13 Oct 2025 20:01:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6D85F8E00B5; Mon, 13 Oct 2025 20:01:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 55B158E0024 for ; Mon, 13 Oct 2025 20:01:39 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 0E68211AA7D for ; Tue, 14 Oct 2025 00:01:39 +0000 (UTC) X-FDA: 83994765918.20.44B4161 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) by imf11.hostedemail.com (Postfix) with ESMTP id 4D49340002 for ; Tue, 14 Oct 2025 00:01:37 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=SmU7VCXj; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf11.hostedemail.com: domain of 34JLtaAYKCAs3plyunrzzrwp.nzxwty58-xxv6lnv.z2r@flex--seanjc.bounces.google.com designates 209.85.216.73 as permitted sender) smtp.mailfrom=34JLtaAYKCAs3plyunrzzrwp.nzxwty58-xxv6lnv.z2r@flex--seanjc.bounces.google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1760400097; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=60W7dGApFCGXHKlXBRGDaLpu3YLgl4WyK3JcN6QaedU=; b=2Wtxi9wuZbWGRGfGxJ6HueufgAylo0LXSXz/P8WAqzPzIS7NjDaPLMr7IeXWz7SCxgMp+p /qA+PeJ8N7EHVdcOcgeDnNSmVy3Ceo9tnJ/mSMYnCOpH1zxUW3skGhKuaKqyVJeFN8YFUz mGYxA2oiag0yhCgsQX68JPHrwf6m10g= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1760400097; a=rsa-sha256; cv=none; b=1Emqj+ccY7n2ZAR/TkwnGB3UMlSjBMk06/X4WSotaz07J8Kuz7uJNNMY9/EITfRPIz/l3K aMZc2YqPiDqcyLDKT1JMBtpQ1jEMj71CBlqcBe857BkHFoz+zhSvWoaqKZ9WoMXzQHsmp+ I+R9j15h7rawVmZ8qz/PzKjhYDFrjhY= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=SmU7VCXj; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf11.hostedemail.com: domain of 34JLtaAYKCAs3plyunrzzrwp.nzxwty58-xxv6lnv.z2r@flex--seanjc.bounces.google.com designates 209.85.216.73 as permitted sender) smtp.mailfrom=34JLtaAYKCAs3plyunrzzrwp.nzxwty58-xxv6lnv.z2r@flex--seanjc.bounces.google.com Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-32eb18b5659so8431523a91.2 for ; Mon, 13 Oct 2025 17:01:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1760400096; x=1761004896; darn=kvack.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=60W7dGApFCGXHKlXBRGDaLpu3YLgl4WyK3JcN6QaedU=; b=SmU7VCXjL5N7tEMa84vuze2DbbaO6sLX4QkeODYXQHek0NrHWaLZL1T7JkOxFbN+79 KnBYAgQX3bpSqhnVi2trFd9gKuvXcMJ0+z3XBHrnqAMQoz85Oo+20mI57kyYlNQlVEUi 8XOZuCyKpkskqQ9ANI7r3iEue1sj/qEngCrsMBzddlP+Ld5XgX2oZ6QDa0t/LlYTXV5/ ZwDXaOUe4VvfcJCFrnqA7YWj+KX7qO/3+T/85nCdIZWQ9IvV3S4Yy8/gCexIIB+cMNjE E+UPfEIy3uveHe12hxNU0WeYoi462cQiTB3862iCia5FhCu/YA/bHJkXgpHKBa6qCccb dajQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760400096; x=1761004896; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=60W7dGApFCGXHKlXBRGDaLpu3YLgl4WyK3JcN6QaedU=; b=Xk2etlf72xqHkWtbO2tGTrEyi9vXjMTJcveMaAJPNGaiO7XLK0G0PMAL5QL83s06Qo 19Zc0Orx5nkuATxIJp/K5pEFWov/tURhIkPuA3YU1dYiUDu3UTz5qyOxCictVkJRxsKG PvXAZTjaM193wKmWX0NhhuPNMZcjP5h6jyzbf8LR8xtD5ayNp6mElHBGhoHvr/n+t1z0 PWHOxoPg6HgdsAYXcT48VNp4EII4tOPKuKtzmEyqGLj361Hc9RMGxfya6D4ZA1uzcNo0 jrfwK/B4uWdUapmQWHiFf0zbM5sI1dwYtgOyL1aonqoKfgqqDPUh0jrtrdl0XpyRYUaw D4hw== X-Forwarded-Encrypted: i=1; AJvYcCU4+T/1PUcJ/qUQSLzdXb35ZZo6vxY4GyXowoZynFoD/78PJLnpeE1LkY1NU4R0pKtde5tdoKJiuA==@kvack.org X-Gm-Message-State: AOJu0Yzkov4WYo+JsTyL1+zN8eUIO0LGTRa2fqiNMDcitdH9xKYdl7C0 2D6DHBQd0bEfoPGn7vS9AagWuD0rYtdKJAlbKlSw3JrTpP++L2+yuqLYHvl6mV/FDN6iHWVJfIb yigQrow== X-Google-Smtp-Source: AGHT+IHFYfnmFjxjbFQp7BMqqD83h/lwfyE6WGt5bwyArJ6H0ox9P/tbWn8NIGRGgabEk9PVFSZMkd4SLvs= X-Received: from pjbbk16.prod.google.com ([2002:a17:90b:810:b0:339:dc19:ae5d]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:38d2:b0:335:2eee:19dc with SMTP id 98e67ed59e1d1-33b5138401amr31287086a91.28.1760400096074; Mon, 13 Oct 2025 17:01:36 -0700 (PDT) Date: Mon, 13 Oct 2025 17:01:34 -0700 In-Reply-To: <20251010153839.151763-20-vschneid@redhat.com> Mime-Version: 1.0 References: <20251010153839.151763-1-vschneid@redhat.com> <20251010153839.151763-20-vschneid@redhat.com> Message-ID: Subject: Re: [PATCH v6 19/29] KVM: VMX: Mark vmx_l1d_should flush and vmx_l1d_flush_cond keys as allowed in .noinstr From: Sean Christopherson To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Josh Poimboeuf , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Paolo Bonzini , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik Content-Type: text/plain; charset="us-ascii" X-Rspam-User: X-Rspamd-Queue-Id: 4D49340002 X-Rspamd-Server: rspam02 X-Stat-Signature: 9m7p5ojhn6gfubwrydhpbzasjec1x3qj X-HE-Tag: 1760400097-252491 X-HE-Meta: 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 ZC0oxPAZ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 10, 2025, Valentin Schneider wrote: > Later commits will cause objtool to warn about static keys being used in > .noinstr sections in order to safely defer instruction patching IPIs > targeted at NOHZ_FULL CPUs. > > These keys are used in .noinstr code, and can be modified at runtime > (/proc/kernel/vmx* write). However it is not expected that they will be > flipped during latency-sensitive operations, and thus shouldn't be a source > of interference wrt the text patching IPI. > > Mark it to let objtool know not to warn about it. Can you elaborate in the changelog on what will happen if the key is toggle? IIUC, smp_text_poke_batch_finish() will force IPIs if noinstr code is being patched. Even just a small footnote like this: Note, smp_text_poke_batch_finish() never defers IPIs if noinstr code is being patched, i.e. this is purely about silencing objtool warnings. to make it clear that there's no bug/race being introduced. > Reported-by: Josh Poimboeuf > Signed-off-by: Valentin Schneider > --- > arch/x86/kvm/vmx/vmx.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index aa157fe5b7b31..dce2bd7375ec8 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -204,8 +204,15 @@ module_param(pt_mode, int, S_IRUGO); > > struct x86_pmu_lbr __ro_after_init vmx_lbr_caps; > > -static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush); > -static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_cond); > +/* > + * Both of these static keys end up being used in .noinstr sections, however > + * they are only modified: > + * - at init > + * - from a /proc/kernel/vmx* write > + * thus during latency-sensitive operations they should remain stable. > + */ > +static DEFINE_STATIC_KEY_FALSE_NOINSTR(vmx_l1d_should_flush); > +static DEFINE_STATIC_KEY_FALSE_NOINSTR(vmx_l1d_flush_cond); > static DEFINE_MUTEX(vmx_l1d_flush_mutex); > > /* Storage for pre module init parameter parsing */ > -- > 2.51.0 >