powerpc/32: Clarify interrupt restores with REST_GPR macro in entry_32.S

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 <rmclure@linux.ibm.com>
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220921065605.1051927-6-rmclure@linux.ibm.com

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 497f04cde7dcb54b8d373d6b70f9a8faef63ea47..e3d43b6e3197c28362a6992ec285dc4b95fcee8a 100644 (file)
--- 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_PPC_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 */