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[203.221.156.192]) by smtp.gmail.com with ESMTPSA id d2sm1840594pjd.29.2021.01.26.02.16.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Jan 2021 02:16:45 -0800 (PST) Date: Tue, 26 Jan 2021 20:16:39 +1000 From: Nicholas Piggin Subject: Re: [PATCH v4 20/23] powerpc/syscall: Do not check unsupported scv vector on PPC32 To: Benjamin Herrenschmidt , Christophe Leroy , Michael Ellerman , msuchanek@suse.de, Paul Mackerras Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: In-Reply-To: MIME-Version: 1.0 Message-Id: <1611656145.efq1cxcpts.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Excerpts from Christophe Leroy's message of January 26, 2021 12:48 am: > Only PPC64 has scv. No need to check the 0x7ff0 trap on PPC32. >=20 > And ignore the scv parameter in syscall_exit_prepare (Save 14 cycles > 346 =3D> 332 cycles) >=20 > Signed-off-by: Christophe Leroy > --- > arch/powerpc/kernel/entry_32.S | 1 - > arch/powerpc/kernel/syscall.c | 7 +++++-- > 2 files changed, 5 insertions(+), 3 deletions(-) >=20 > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_3= 2.S > index 9922a04650f7..6ae9c7bcb06c 100644 > --- a/arch/powerpc/kernel/entry_32.S > +++ b/arch/powerpc/kernel/entry_32.S > @@ -343,7 +343,6 @@ transfer_to_syscall: > =20 > ret_from_syscall: > addi r4,r1,STACK_FRAME_OVERHEAD > - li r5,0 > bl syscall_exit_prepare > #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) > /* If the process has its own DBCR0 value, load it up. The internal > diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.= c > index 476909b11051..30f8a397a522 100644 > --- a/arch/powerpc/kernel/syscall.c > +++ b/arch/powerpc/kernel/syscall.c > @@ -86,7 +86,7 @@ notrace long system_call_exception(long r3, long r4, lo= ng r5, > local_irq_enable(); > =20 > if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) { > - if (unlikely(regs->trap =3D=3D 0x7ff0)) { > + if (IS_ENABLED(CONFIG_PPC64) && unlikely(regs->trap =3D=3D 0x7ff0)) { > /* Unsupported scv vector */ > _exception(SIGILL, regs, ILL_ILLOPC, regs->nip); > return regs->gpr[3]; > @@ -109,7 +109,7 @@ notrace long system_call_exception(long r3, long r4, = long r5, > r8 =3D regs->gpr[8]; > =20 > } else if (unlikely(r0 >=3D NR_syscalls)) { > - if (unlikely(regs->trap =3D=3D 0x7ff0)) { > + if (IS_ENABLED(CONFIG_PPC64) && unlikely(regs->trap =3D=3D 0x7ff0)) { Perhaps this could be hidden behind a function like trap_is_scv()? trap_is_unsupported_scv() ? Thanks, Nick