powerpc/64s: Remove EXSLB interrupt save area

SLB faults should not be taken while the PACA save areas are live, all
memory accesses should be fetches from the kernel text, and access to
PACA and the current stack, before C code is called or any other
accesses are made.

All of these have pinned SLBs so will not take a SLB fault. Therefore
EXSLB is not be required.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210208063406.331655-1-npiggin@gmail.com

diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 169e687..ec18ac8 100644 (file)
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -109,8 +109,7 @@ struct paca_struct {
         */
        /* used for most interrupts/exceptions */
        u64 exgen[EX_SIZE] __attribute__((aligned(0x80)));
-       u64 exslb[EX_SIZE];     /* used for SLB/segment table misses
-                                * on the linear mapping */
+
        /* SLB related definitions */
        u16 vmalloc_sllp;
        u8 slb_cache_ptr;

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index b12d7c0..31edd9b 100644 (file)
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -255,7 +255,6 @@ int main(void)
 #endif /* CONFIG_PPC_MM_SLICES */
        OFFSET(PACA_EXGEN, paca_struct, exgen);
        OFFSET(PACA_EXMC, paca_struct, exmc);
-       OFFSET(PACA_EXSLB, paca_struct, exslb);
        OFFSET(PACA_EXNMI, paca_struct, exnmi);
 #ifdef CONFIG_PPC_PSERIES
        OFFSET(PACALPPACAPTR, paca_struct, lppaca_ptr);

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index de3e335..a4bd3c1 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1412,13 +1412,9 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
  *   on user-handler data structures.
  *
  *   KVM: Same as 0x300, DSLB must test for KVM guest.
- *
- * A dedicated save area EXSLB is used (XXX: but it actually need not be
- * these days, we could use EXGEN).
  */
 INT_DEFINE_BEGIN(data_access_slb)
        IVEC=0x380
-       IAREA=PACA_EXSLB
        IDAR=1
        IKVM_SKIP=1
        IKVM_REAL=1
@@ -1501,7 +1497,6 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
  */
 INT_DEFINE_BEGIN(instruction_access_slb)
        IVEC=0x480
-       IAREA=PACA_EXSLB
        IISIDE=1
        IDAR=1
 #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE