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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 77E6AC02183 for ; Fri, 17 Jan 2025 17:20:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:Message-ID: References:Mime-Version:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=G4vv5al9TlXOnkhC9icLM9RkHToU8TnqdA30sRoh++k=; b=cW5NBicow8IJFxS6il1hrNLjiJ FW6poI/EK5b9xxl1tw7MXao6mnUc1JCThyzjRF36n4JBXZ7xGCDKp9+BTuCapV6bli8Lnt3oGknWM j18SGBNwQYx4sAC+xb17xYZN8Q86BV3+mb7IgT1ikmphTBvaSIoqo9fBUlc9vyLIfsOuhJyKC206g hUnU88B7cLiIFmLqI6rrr7Kv+GfOlGXeUHLSYF55mjxCLRKgKkqYZ/p2ayIWxtrPUWWlw7hGxP8NS BmnmxvwjwK6VHFT2PaTUly7kkMDYBtyu6g+RPmF1x+jY617xzGrf4IIg3Ck2oCYZrQDIodThrceYM YUXOAb/Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tYq1W-00000000wlO-0IGc; Fri, 17 Jan 2025 17:20:46 +0000 Received: from mail-pl1-x649.google.com ([2607:f8b0:4864:20::649]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tYpwQ-00000000w3Y-34Cn for linux-riscv@lists.infradead.org; Fri, 17 Jan 2025 17:15:32 +0000 Received: by mail-pl1-x649.google.com with SMTP id d9443c01a7336-2178115051dso44450825ad.1 for ; Fri, 17 Jan 2025 09:15:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1737134129; x=1737738929; darn=lists.infradead.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=/pcx17eniD+ASjh3teIfjrJN/d55a+1SMCIjE05N6Y0=; b=zttRI2SODOA2JjE61Y/01AnIpRrQYvAzSo00TWby6t6n99RBppCqDZRk81QL/ciooo NtwFq0hbxbaLPiGE63AwiIIs6treFB9pxTpKh0ujrbyRK9BRZAcygl/BocEQO86m5C2f Ay79PMYLs5AVRCy+utQ2t4HDt/DFRW+wFrLImBbWNlxfgMn8gSqzYEyb/nVVHgcQnfQR IcKV801YWlGXapQO/zE0dEpj+n0HadRTyOF8geBeXTKmAvNdNsGswHetiySjZJTTrzTq OrkNbc0dZtpV+32Q8mamHlXc3q/cR8JpkeX4cAHfnct5h+g2BtJBYHfGiYXyb3ivLs8q NZ+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1737134129; x=1737738929; 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=/pcx17eniD+ASjh3teIfjrJN/d55a+1SMCIjE05N6Y0=; b=CS/UKwfM/CM6cJHlJ2VzvYo7z6U+x8XNLYHjRilwzCC206B5AveoaEt8CITpS9kQ3V QoNLXFekSHNBAzHL0X1/CF+VLiPvpJvo3qGgp5JA/9T5M/7GsB25xMWgdmtenKbpLs0U ubALXBk0a41AlaUu81m4l1l6JI18ips2wyJnIUp1T5vbEpqSdcf29JZSG5pFiYc2ZBTp 01Gl186SIj1huPBLXNcC1pYkRbmf1jSBRQGhLWFqXqs84yp10YQ4SwMbe2XO1czlGyWh vfmPtaq2aIVVM7YOkt34UJ5DTg0hjBIR1qxnpVbwZT5Lxbde7wLuCntW4y00COpGWk8X DPDA== X-Forwarded-Encrypted: i=1; AJvYcCU6toT6gycOyEVST/FsNfI5BVadBZn+8YttU1ExGdJqEbnMtxLlXgV+EQrEAnNfpgmIWgnM+RE3GB2RNQ==@lists.infradead.org X-Gm-Message-State: AOJu0YwSjzyOURE7sKOHQFCKTzvbCLAmqkILmI/Q9oi+xyUNpyY9T9DT 8E3e5cC7dRrGDarUn5EnDhdlovqR6nFaA/zOWXlT8f8hy9TZmkFrPNyU2W0NLcDRk54buYrvwdr t8A== X-Google-Smtp-Source: AGHT+IFBt8EUJmCBrYJSR6SbgIXxnZj6fm10TNGjaAj4XRK+x0dRIzGirCE9VGAaKkDPtl0zEYTqCFRnILs= X-Received: from pfbcv2.prod.google.com ([2002:a05:6a00:44c2:b0:725:a760:4c72]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:148d:b0:725:eb85:f802 with SMTP id d2e1a72fcca58-72daf930e3cmr5815077b3a.2.1737134128872; Fri, 17 Jan 2025 09:15:28 -0800 (PST) Date: Fri, 17 Jan 2025 09:15:27 -0800 In-Reply-To: Mime-Version: 1.0 References: <20250114175143.81438-1-vschneid@redhat.com> <20250114175143.81438-26-vschneid@redhat.com> Message-ID: Subject: Re: [PATCH v4 25/30] context_tracking,x86: Defer kernel text patching IPIs From: Sean Christopherson To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, x86@kernel.org, virtualization@lists.linux.dev, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-perf-users@vger.kernel.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, bpf@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, Peter Zijlstra , Nicolas Saenz Julienne , Juergen Gross , Ajay Kaher , Alexey Makhalov , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , Boris Ostrovsky , Josh Poimboeuf , Pawan Gupta , Paolo Bonzini , Andy Lutomirski , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Juri Lelli , Clark Williams , Yair Podemsky , Tomas Glozar , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Kees Cook , Andrew Morton , Christoph Hellwig , Shuah Khan , Sami Tolvanen , Miguel Ojeda , Alice Ryhl , "Mike Rapoport (Microsoft)" , Samuel Holland , Rong Xu , Geert Uytterhoeven , Yosry Ahmed , "Kirill A. Shutemov" , "Masami Hiramatsu (Google)" , Jinghao Jia , Luis Chamberlain , Randy Dunlap , Tiezhu Yang X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250117_091530_762342_742A0F32 X-CRM114-Status: GOOD ( 21.62 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Fri, Jan 17, 2025, Valentin Schneider wrote: > On 14/01/25 13:13, Sean Christopherson wrote: > > On Tue, Jan 14, 2025, Valentin Schneider wrote: > >> +/** > >> + * is_kernel_noinstr_text - checks if the pointer address is located in the > >> + * .noinstr section > >> + * > >> + * @addr: address to check > >> + * > >> + * Returns: true if the address is located in .noinstr, false otherwise. > >> + */ > >> +static inline bool is_kernel_noinstr_text(unsigned long addr) > >> +{ > >> + return addr >= (unsigned long)__noinstr_text_start && > >> + addr < (unsigned long)__noinstr_text_end; > >> +} > > > > This doesn't do the right thing for modules, which matters because KVM can be > > built as a module on x86, and because context tracking understands transitions > > to GUEST mode, i.e. CPUs that are running in a KVM guest will be treated as not > > being in the kernel, and thus will have IPIs deferred. If KVM uses a static key > > or branch between guest_state_enter_irqoff() and guest_state_exit_irqoff(), the > > patching code won't wait for CPUs to exit guest mode, i.e. KVM could theoretically > > use the wrong static path. > > AFAICT guest_state_{enter,exit}_irqoff() are only used in noinstr functions > and thus such a static key usage should at the very least be caught and > warned about by objtool - when this isn't built as a module. That doesn't magically do the right thing though. If KVM is built as a module, is_kernel_noinstr_text() will get false negatives even for static keys/branches that are annotaed as NOINSTR. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv