From 52ae92cc290f0506eef9ad5466bb453ce4a9e80e Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Fri, 12 Mar 2021 12:50:11 +0000 Subject: [PATCH] powerpc/40x: Don't use SPRN_SPRG_SCRATCH0/1 in TLB miss handlers SPRN_SPRG_SCRATCH5 is used to save SPRN_PID. SPRN_SPRG_SCRATCH6 is already available. SPRN_PID is only 8 bits. We have r12 that contains CR. We only need to preserve CR0, so we have space available in r12 to save PID. Keep PID in r12 and free up SPRN_SPRG_SCRATCH5. Then In TLB miss handlers, instead of using SPRN_SPRG_SCRATCH0 and SPRN_SPRG_SCRATCH1, use SPRN_SPRG_SCRATCH5 and SPRN_SPRG_SCRATCH6 to avoid future conflicts with normal exception prologs. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/4cdaa85d38e14d594ba902424060ec55babf2c42.1615552866.git.christophe.leroy@csgroup.eu --- arch/powerpc/kernel/head_40x.S | 39 ++++++++++++++++------------------ 1 file changed, 18 insertions(+), 21 deletions(-) diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S index 24724a7dad49a..383238a98f776 100644 --- a/arch/powerpc/kernel/head_40x.S +++ b/arch/powerpc/kernel/head_40x.S @@ -249,13 +249,13 @@ _ENTRY(saved_ksp_limit) * load TLB entries from the page table if they exist. */ START_EXCEPTION(0x1100, DTLBMiss) - mtspr SPRN_SPRG_SCRATCH0, r10 /* Save some working registers */ - mtspr SPRN_SPRG_SCRATCH1, r11 + mtspr SPRN_SPRG_SCRATCH5, r10 /* Save some working registers */ + mtspr SPRN_SPRG_SCRATCH6, r11 mtspr SPRN_SPRG_SCRATCH3, r12 mtspr SPRN_SPRG_SCRATCH4, r9 mfcr r12 mfspr r9, SPRN_PID - mtspr SPRN_SPRG_SCRATCH5, r9 + rlwimi r12, r9, 0, 0xff mfspr r10, SPRN_DEAR /* Get faulting address */ /* If we are faulting a kernel address, we have to use the @@ -316,13 +316,12 @@ _ENTRY(saved_ksp_limit) /* The bailout. Restore registers to pre-exception conditions * and call the heavyweights to help us out. */ - mfspr r9, SPRN_SPRG_SCRATCH5 - mtspr SPRN_PID, r9 - mtcr r12 + mtspr SPRN_PID, r12 + mtcrf 0x80, r12 mfspr r9, SPRN_SPRG_SCRATCH4 mfspr r12, SPRN_SPRG_SCRATCH3 - mfspr r11, SPRN_SPRG_SCRATCH1 - mfspr r10, SPRN_SPRG_SCRATCH0 + mfspr r11, SPRN_SPRG_SCRATCH6 + mfspr r10, SPRN_SPRG_SCRATCH5 b DataStorage /* 0x1200 - Instruction TLB Miss Exception @@ -330,13 +329,13 @@ _ENTRY(saved_ksp_limit) * registers and bailout to a different point. */ START_EXCEPTION(0x1200, ITLBMiss) - mtspr SPRN_SPRG_SCRATCH0, r10 /* Save some working registers */ - mtspr SPRN_SPRG_SCRATCH1, r11 + mtspr SPRN_SPRG_SCRATCH5, r10 /* Save some working registers */ + mtspr SPRN_SPRG_SCRATCH6, r11 mtspr SPRN_SPRG_SCRATCH3, r12 mtspr SPRN_SPRG_SCRATCH4, r9 mfcr r12 mfspr r9, SPRN_PID - mtspr SPRN_SPRG_SCRATCH5, r9 + rlwimi r12, r9, 0, 0xff mfspr r10, SPRN_SRR0 /* Get faulting address */ /* If we are faulting a kernel address, we have to use the @@ -397,13 +396,12 @@ _ENTRY(saved_ksp_limit) /* The bailout. Restore registers to pre-exception conditions * and call the heavyweights to help us out. */ - mfspr r9, SPRN_SPRG_SCRATCH5 - mtspr SPRN_PID, r9 - mtcr r12 + mtspr SPRN_PID, r12 + mtcrf 0x80, r12 mfspr r9, SPRN_SPRG_SCRATCH4 mfspr r12, SPRN_SPRG_SCRATCH3 - mfspr r11, SPRN_SPRG_SCRATCH1 - mfspr r10, SPRN_SPRG_SCRATCH0 + mfspr r11, SPRN_SPRG_SCRATCH6 + mfspr r10, SPRN_SPRG_SCRATCH5 b InstructionAccess EXCEPTION(0x1300, Trap_13, unknown_exception, EXC_XFER_STD) @@ -543,13 +541,12 @@ finish_tlb_load: /* Done...restore registers and get out of here. */ - mfspr r9, SPRN_SPRG_SCRATCH5 - mtspr SPRN_PID, r9 - mtcr r12 + mtspr SPRN_PID, r12 + mtcrf 0x80, r12 mfspr r9, SPRN_SPRG_SCRATCH4 mfspr r12, SPRN_SPRG_SCRATCH3 - mfspr r11, SPRN_SPRG_SCRATCH1 - mfspr r10, SPRN_SPRG_SCRATCH0 + mfspr r11, SPRN_SPRG_SCRATCH6 + mfspr r10, SPRN_SPRG_SCRATCH5 rfi /* Should sync shadow TLBs */ b . /* prevent prefetch past rfi */ -- 2.30.2