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 <rmcl...@linux.ibm.com>
> Reported-by: Christophe Leroy <christophe.le...@csgroup.eu>Reviewed-by: Nicholas Piggin <npig...@gmail.com> > --- > 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_32.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 > > -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 > > #ifdef CONFIG_44x > @@ -260,9 +258,8 @@ fast_exception_return: > beq 3f /* if not, we've got problems */ > #endif > > -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 */ > > -- > 2.34.1
