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[109.252.193.159]) by smtp.googlemail.com with ESMTPSA id n5sm2017481lfl.175.2020.11.09.23.44.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Nov 2020 23:44:14 -0800 (PST) Subject: Re: [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel compilation error To: Ard Biesheuvel Cc: Russell King - ARM Linux admin , Kees Cook , Nick Desaulniers , Linux Kernel Mailing List , clang-built-linux , Ingo Molnar , Linux ARM References: <202010211637.7CFD8435@keescook> <773fbdb0-5fc4-ab39-e72d-89845faa4c6d@gmail.com> <202010212028.32E8A5EF9B@keescook> <1d2e2b5d-3035-238c-d2ca-14c0c209a6a1@gmail.com> <20201022161118.GP1551@shell.armlinux.org.uk> <20201022162334.GQ1551@shell.armlinux.org.uk> <20201022174826.GS1551@shell.armlinux.org.uk> From: Dmitry Osipenko Message-ID: Date: Tue, 10 Nov 2020 10:44:14 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 09.11.2020 10:25, Ard Biesheuvel пишет: ... >>> So the options are >>> >>> a) merge my patch that adds 2 bytes of opcode to the Thumb2 build >>> b) merge Dmitry's patch that adds an unconditional literal load to all builds >>> c) remove kernel mode handling from vfp_support_entry() [my other patch] >>> d) move sections around so that vfp_kmode_exception is guaranteed to >>> be in range. >>> e) do nothing ... >> The performance argument is questionable to me, to be honest. In >> practice the performance difference should be absolutely negligible for >> either of the proposed options, it should stay in a noise even if >> somebody thoroughly counting cycles, IMO. >> >> I'm still thinking that the best option will be to apply a). >> > > Can we take that as an acked-by? Are you asking me for the ack? I think this is a more appropriate question to Russel. I'm not arm/ maintainer, but could give r-b and t-b. If you're going to follow approach that I'm suggesting with a) + d), then could you please resend the two patches in a single series? The first one-line patch-fix should contain the fixes tag.