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[118.208.203.28]) by smtp.gmail.com with ESMTPSA id b2-20020a170902d50200b0017315b11bb8sm21552853plg.213.2022.09.19.17.51.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Sep 2022 17:51:23 -0700 (PDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 20 Sep 2022 10:51:18 +1000 Message-Id: To: "Rohan McLure" , Subject: Re: [PATCH 05/23] powerpc/32: Clarify interrupt restores with REST_GPR macro in entry_32.S From: "Nicholas Piggin" X-Mailer: aerc 0.11.0 References: <20220916053300.786330-1-rmclure@linux.ibm.com> <20220916053300.786330-6-rmclure@linux.ibm.com> In-Reply-To: <20220916053300.786330-6-rmclure@linux.ibm.com> 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: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri Sep 16, 2022 at 3:32 PM AEST, Rohan McLure wrote: > Restoring the register state of the interrupted thread involves issuing > a large number of predictable loads to the kernel stack frame. Issue the > REST_GPR{,S} macros to clearly signal when this is happening, and bunch > together restores at the end of the interrupt handler where the saved > value is not consumed earlier in the handler code. > > Signed-off-by: Rohan McLure > Reported-by: Christophe Leroy Reviewed-by: Nicholas Piggin > --- > V2 -> V3: New patch. > V3 -> V4: Minimise restores in the unrecoverable window between > restoring SRR0/1 and return from interrupt. > --- > arch/powerpc/kernel/entry_32.S | 33 +++++++++++++------------------- > 1 file changed, 13 insertions(+), 20 deletions(-) > > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_3= 2.S > index 44dfce9a60c5..e4b694cebc44 100644 > --- a/arch/powerpc/kernel/entry_32.S > +++ b/arch/powerpc/kernel/entry_32.S > @@ -68,7 +68,7 @@ prepare_transfer_to_handler: > lwz r9,_MSR(r11) /* if sleeping, clear MSR.EE */ > rlwinm r9,r9,0,~MSR_EE > lwz r12,_LINK(r11) /* and return to address in LR */ > - lwz r2, GPR2(r11) > + REST_GPR(2, r11) > b fast_exception_return > _ASM_NOKPROBE_SYMBOL(prepare_transfer_to_handler) > #endif /* CONFIG_PPC_BOOK3S_32 || CONFIG_E500 */ > @@ -144,7 +144,7 @@ ret_from_syscall: > lwz r7,_NIP(r1) > lwz r8,_MSR(r1) > cmpwi r3,0 > - lwz r3,GPR3(r1) > + REST_GPR(3, r1) > syscall_exit_finish: > mtspr SPRN_SRR0,r7 > mtspr SPRN_SRR1,r8 > @@ -152,8 +152,8 @@ syscall_exit_finish: > bne 3f > mtcr r5 > =20 > -1: lwz r2,GPR2(r1) > - lwz r1,GPR1(r1) > +1: REST_GPR(2, r1) > + REST_GPR(1, r1) > rfi > #ifdef CONFIG_40x > b . /* Prevent prefetch past rfi */ > @@ -165,10 +165,8 @@ syscall_exit_finish: > REST_NVGPRS(r1) > mtctr r4 > mtxer r5 > - lwz r0,GPR0(r1) > - lwz r3,GPR3(r1) > - REST_GPRS(4, 11, r1) > - lwz r12,GPR12(r1) > + REST_GPR(0, r1) > + REST_GPRS(3, 12, r1) > b 1b > =20 > #ifdef CONFIG_44x > @@ -260,9 +258,8 @@ fast_exception_return: > beq 3f /* if not, we've got problems */ > #endif > =20 > -2: REST_GPRS(3, 6, r11) > - lwz r10,_CCR(r11) > - REST_GPRS(1, 2, r11) > +2: lwz r10,_CCR(r11) > + REST_GPRS(1, 6, r11) > mtcr r10 > lwz r10,_LINK(r11) > mtlr r10 > @@ -277,7 +274,7 @@ fast_exception_return: > mtspr SPRN_SRR0,r12 > REST_GPR(9, r11) > REST_GPR(12, r11) > - lwz r11,GPR11(r11) > + REST_GPR(11, r11) > rfi > #ifdef CONFIG_40x > b . /* Prevent prefetch past rfi */ > @@ -454,9 +451,8 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return) > lwz r3,_MSR(r1); \ > andi. r3,r3,MSR_PR; \ > bne interrupt_return; \ > - lwz r0,GPR0(r1); \ > - lwz r2,GPR2(r1); \ > - REST_GPRS(3, 8, r1); \ > + REST_GPR(0, r1); \ > + REST_GPRS(2, 8, r1); \ > lwz r10,_XER(r1); \ > lwz r11,_CTR(r1); \ > mtspr SPRN_XER,r10; \ > @@ -475,11 +471,8 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return) > lwz r12,_MSR(r1); \ > mtspr exc_lvl_srr0,r11; \ > mtspr exc_lvl_srr1,r12; \ > - lwz r9,GPR9(r1); \ > - lwz r12,GPR12(r1); \ > - lwz r10,GPR10(r1); \ > - lwz r11,GPR11(r1); \ > - lwz r1,GPR1(r1); \ > + REST_GPRS(9, 12, r1); \ > + REST_GPR(1, r1); \ > exc_lvl_rfi; \ > b .; /* prevent prefetch past exc_lvl_rfi */ > =20 > --=20 > 2.34.1