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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=/Z8FCJhJc8vaF3pv6iIl59Qxo3H1jiWyBrvdIdYTFZo=; b=ER/62PRS+H8Ec8mV22R2v5eczkkdzy8QONJxFZ4v2PDI5qUm46BsQO0JJw3XF80P5r Qj94XAjCLdTqXzreGZ/KUyOsQyuy+PJDPsEPNTe50GW5x7e2qSde1zzrWi5z+Io+gmP1 s+7eQaR+V7oJeUmLXCYtcVUX8xcWTwrYHR1r4r48Zi+Pj3PYUlBVmO6Mwv0qRupUq9Pi T2wygSu+j2Q6voQ2He4aLa2uBJXvA83CJQO70Q8TxHwygBohOXjaN0dPGOGjub2KGZa7 X745EpZHEU86Vcu1ddOg+9anlXdXBrZq2u9lWCRkO65trDelwresvk0MkGR5u/sdQXLt bdyA== X-Gm-Message-State: APjAAAVIVtVyzc+1trnShNtMr7pXTxHWQ8RXVpX0GSHPAPdLM+2qxuuS bMw5rlb0IxeZXMVFpZ2PIgZqp3Jwf3C30gyjfSl7dg== X-Google-Smtp-Source: APXvYqxGDaeQRy8RlmXm5+Hfyoixl8MwWZkSG4wSuF+yDcsB9jopivDI9V4aE5Iq+b3wnA8tPQTJZqZAcyU0fNo0u7s= X-Received: by 2002:a5d:69c8:: with SMTP id s8mr20980659wrw.32.1570545553804; Tue, 08 Oct 2019 07:39:13 -0700 (PDT) MIME-Version: 1.0 References: <20191004120430.11929-1-ard.biesheuvel@linaro.org> <20191004120430.11929-2-ard.biesheuvel@linaro.org> <20191008143537.GA14523@lakrids.cambridge.arm.com> In-Reply-To: <20191008143537.GA14523@lakrids.cambridge.arm.com> From: Ard Biesheuvel Date: Tue, 8 Oct 2019 16:39:02 +0200 Message-ID: Subject: Re: [RFC/RFT PATCH 01/16] arm64: cpufeature: Detect SSBS and advertise to userspace To: Mark Rutland X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191008_073916_550469_90BB62D2 X-CRM114-Status: GOOD ( 18.14 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Suzuki K Poulose , Catalin Marinas , Will Deacon , Jeremy Linton , Andre Przywara , Marc Zyngier , Will Deacon , linux-arm-kernel Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 8 Oct 2019 at 16:35, Mark Rutland wrote: > > Hi Ard, > > I have a few general backport notes below, and one issue with this > patch/series. > > On Fri, Oct 04, 2019 at 02:04:15PM +0200, Ard Biesheuvel wrote: > > From: Will Deacon > > > > Armv8.5 introduces a new PSTATE bit known as Speculative Store Bypass > > Safe (SSBS) which can be used as a mitigation against Spectre variant 4. > > > > Additionally, a CPU may provide instructions to manipulate PSTATE.SSBS > > directly, so that userspace can toggle the SSBS control without trapping > > to the kernel. > > > > This patch probes for the existence of SSBS and advertise the new instructions > > to userspace if they exist. > > > > Reviewed-by: Suzuki K Poulose > > Signed-off-by: Will Deacon > > Signed-off-by: Catalin Marinas > > (cherry picked from commit d71be2b6c0e19180b5f80a6d42039cc074a693a2) > > This should be the first line, formatted like: > > commit d71be2b6c0e19180b5f80a6d42039cc074a693a2 upstream. > > ... as documented in Documentation/process/stable-kernel-rules.rst. > I see that's sometimes not followed, but I think we should stick to that > unless there's a strong reason not to. > Indeed, but I have adopted the [ Upstream commit xxx ] style in the meantime in [0] (and [1]) > If you had to make any substantial changes, I'd recommend a note above > your S-o-B, e.g > > [v4.9: Renamed foo() to bar() to match xxyyzz()] > Sure. > ... and regardless I usually add a [vX.Y backport] trailing my S-o-B to > make it clear from the log where that happened. > > For this patch specifically, I believe that you also need to backport > commit: > > f54dada8274643e3 ("arm64: fix SSBS sanitization") > > ... which fixes the SSBS bit being cleared across sigreturns. > Coming up in 05/16 > Otherwise, this patch looks good to me. > Thanks. [0] https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=ssbs-v4.19-stable [1] https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=ssbs-v4.14-stable _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel