Re: [PATCH v2 03/10] powerpc/6xx: Store PGDIR physical address in a SPRG
From: Christophe Leroy
Date: Thu Mar 07 2019 - 13:14:57 EST
Hi,
On 03/07/2019 02:11 PM, Guenter Roeck wrote:
Hi,
On Thu, Feb 21, 2019 at 10:37:55AM +0000, Christophe Leroy wrote:
Use SPRN_SPRG2 to store the current thread PGDIR and
avoid reading thread_struct.pgdir at every TLB miss.
This patch causes a number of silent (no crash) qemu boot stalls
in -next. See
https://kerneltests.org/builders/qemu-ppc-next/builds/1080/steps/qemubuildcommand/logs/stdio
for an example.
Oops.
Could you try the fix below ?
diff --git a/arch/powerpc/kernel/cpu_setup_6xx.S
b/arch/powerpc/kernel/cpu_setup_6xx.S
index 6f1c11e0691f..7534ecff5e92 100644
--- a/arch/powerpc/kernel/cpu_setup_6xx.S
+++ b/arch/powerpc/kernel/cpu_setup_6xx.S
@@ -24,9 +24,6 @@ BEGIN_MMU_FTR_SECTION
li r10,0
mtspr SPRN_SPRG_603_LRU,r10 /* init SW LRU tracking */
END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
- lis r10, (swapper_pg_dir - PAGE_OFFSET)@h
- ori r10, r10, (swapper_pg_dir - PAGE_OFFSET)@l
- mtspr SPRN_SPRG_PGDIR, r10
BEGIN_FTR_SECTION
bl __init_fpu_registers
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index ce6a972f2584..48051c8977c5 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -855,6 +855,9 @@ __secondary_start:
li r3,0
stw r3, RTAS_SP(r4) /* 0 => not in RTAS */
#endif
+ lis r4, (swapper_pg_dir - PAGE_OFFSET)@h
+ ori r4, r4, (swapper_pg_dir - PAGE_OFFSET)@l
+ mtspr SPRN_SPRG_PGDIR, r4
/* enable MMU and jump to start_secondary */
li r4,MSR_KERNEL
@@ -942,6 +945,9 @@ start_here:
li r3,0
stw r3, RTAS_SP(r4) /* 0 => not in RTAS */
#endif
+ lis r4, (swapper_pg_dir - PAGE_OFFSET)@h
+ ori r4, r4, (swapper_pg_dir - PAGE_OFFSET)@l
+ mtspr SPRN_SPRG_PGDIR, r4
/* stack */
lis r1,init_thread_union@ha
diff --git a/arch/powerpc/mm/hash_low_32.S b/arch/powerpc/mm/hash_low_32.S
index 1f13494efb2b..587e4550d83e 100644
--- a/arch/powerpc/mm/hash_low_32.S
+++ b/arch/powerpc/mm/hash_low_32.S
@@ -70,12 +70,12 @@ _GLOBAL(hash_page)
lis r0,KERNELBASE@h /* check if kernel address */
cmplw 0,r4,r0
ori r3,r3,_PAGE_USER|_PAGE_PRESENT /* test low addresses as user */
- mfspr r5, SPRN_SPRG_PGDIR /* virt page-table root */
+ mfspr r5, SPRN_SPRG_PGDIR /* phys page-table root */
blt+ 112f /* assume user more likely */
- lis r5,swapper_pg_dir@ha /* if kernel address, use */
- addi r5,r5,swapper_pg_dir@l /* kernel page table */
+ lis r5, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */
+ addi r5 ,r5 , (swapper_pg_dir - PAGE_OFFSET)@l /* kernel page table */
rlwimi r3,r9,32-12,29,29 /* MSR_PR -> _PAGE_USER */
-112: tophys(r5, r5)
+112:
#ifndef CONFIG_PTE_64BIT
rlwimi r5,r4,12,20,29 /* insert top 10 bits of address */
lwz r8,0(r5) /* get pmd entry */
Thanks
Christophe
Unfortunately, it is not possible to revert the patch due to subsequent
patches, so I was unable to test a revert.
Bisect log is attached.
Guenter
---
# bad: [cf08baa29613dd899954089e7cc7dba1d478b365] Add linux-next specific files for 20190306
# good: [1c163f4c7b3f621efff9b28a47abb36f7378d783] Linux 5.0
git bisect start 'HEAD' 'v5.0'
# bad: [6cc8f3499ec8d31904ab9083980a91736512cb37] Merge remote-tracking branch 'vfs/for-next'
git bisect bad 6cc8f3499ec8d31904ab9083980a91736512cb37
# good: [63bdf4284c38a48af21745ceb148a087b190cd21] Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
git bisect good 63bdf4284c38a48af21745ceb148a087b190cd21
# good: [520b5fc601ab760fee7ea0c403b42d04e8ebfd93] Merge remote-tracking branch 'arm-soc/for-next'
git bisect good 520b5fc601ab760fee7ea0c403b42d04e8ebfd93
# bad: [d7f54e4e0d4e90f5df78da8d6a830bafad3b535a] Merge remote-tracking branch 'xtensa/xtensa-for-next'
git bisect bad d7f54e4e0d4e90f5df78da8d6a830bafad3b535a
# good: [0c1a78523542fb3d2e6c5ac7955c8ca8f6482e6f] Merge remote-tracking branch 'clk/clk-next'
git bisect good 0c1a78523542fb3d2e6c5ac7955c8ca8f6482e6f
# bad: [fb0b0a73b223fc113e961b1d921322844e9c30d9] powerpc: Enable kcov
git bisect bad fb0b0a73b223fc113e961b1d921322844e9c30d9
# good: [d0055df0c9c1471c389197a69f43e300185a75aa] Merge branch 'topic/dma' into next
git bisect good d0055df0c9c1471c389197a69f43e300185a75aa
# good: [0df977eafc792a5365a7f81d8d5920132e03afad] powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS
git bisect good 0df977eafc792a5365a7f81d8d5920132e03afad
# bad: [665bed2386e5dc29844ad78c7ef1464664b103ec] powerpc/8xx: replace most #ifdef by IS_ENABLED() in 8xx_mmu.c
git bisect bad 665bed2386e5dc29844ad78c7ef1464664b103ec
# bad: [78ca1108b10927b3d068c8da91352b0f4cd01fc5] powerpc/book3s32: Reorder _PAGE_XXX flags to simplify TLB handling
git bisect bad 78ca1108b10927b3d068c8da91352b0f4cd01fc5
# bad: [a8a121995b2e4f227fddc534c6bd5f1c02cbe2ee] powerpc/603: Don't handle kernel page TLB misses when not need
git bisect bad a8a121995b2e4f227fddc534c6bd5f1c02cbe2ee
# bad: [2c12393f577396a51b7e0537bd3eb29dcc26dc1b] powerpc/603: use physical address directly in TLB miss handlers.
git bisect bad 2c12393f577396a51b7e0537bd3eb29dcc26dc1b
# bad: [93c4a162b014d238a287f8264adb25c009c79e61] powerpc/6xx: Store PGDIR physical address in a SPRG
git bisect bad 93c4a162b014d238a287f8264adb25c009c79e61
# first bad commit: [93c4a162b014d238a287f8264adb25c009c79e61] powerpc/6xx: Store PGDIR physical address in a SPRG