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[14.201.150.91]) by smtp.gmail.com with ESMTPSA id b14sm185543pfi.74.2021.02.09.17.57.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Feb 2021 17:57:45 -0800 (PST) Date: Wed, 10 Feb 2021 11:57:40 +1000 From: Nicholas Piggin Subject: Re: [PATCH v5 18/22] powerpc/syscall: Remove FULL_REGS verification in system_call_exception To: Benjamin Herrenschmidt , Christophe Leroy , Michael Ellerman , msuchanek@suse.de, Paul Mackerras References: <6bef4d9ba0cba50160d13e344ee4627ebdf801dc.1612796617.git.christophe.leroy@csgroup.eu> <1612836023.l122pe2n2b.astroid@bobo.none> In-Reply-To: MIME-Version: 1.0 Message-Id: <1612922197.2b51jxzeqs.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Christophe Leroy's message of February 10, 2021 12:31 am: >=20 >=20 > Le 09/02/2021 =C3=A0 03:02, Nicholas Piggin a =C3=A9crit=C2=A0: >> Excerpts from Christophe Leroy's message of February 9, 2021 1:10 am: >>> For book3s/64, FULL_REGS() is 'true' at all time, so the test voids. >>> For others, non volatile registers are saved inconditionally. >>> >>> So the verification is pointless. >>> >>> Should one fail to do it, it would anyway be caught by the >>> CHECK_FULL_REGS() in copy_thread() as we have removed the >>> special versions ppc_fork() and friends. >>> >>> null_syscall benchmark reduction 4 cycles (332 =3D> 328 cycles) >>=20 >> I wonder if we rather make a CONFIG option for a bunch of these simpler >> debug checks here (and also in interrupt exit, wrappers, etc) rather >> than remove them entirely. >=20 > We can drop this patch if you prefer. Anyway, like book3s/64, once ppc32 = also do interrupt=20 > entry/exit in C, FULL_REGS() will already return true. Sure let's do that. Thanks, Nick