Drop "MIPS: tlbex: Fix build_restore_pagemask KScratch restore"
This was included in 4.19.81.
This commit is contained in:
Ben Hutchings
parent
beb8c412e8
commit
8c4ce65f70
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@ -1365,9 +1365,6 @@ linux (4.19.81-1) UNRELEASED; urgency=medium
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process context" using kthread_work
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- workqueue: rework
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[ Aurelien Jarno ]
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* [mips*] tlbex: Fix build_restore_pagemask KScratch restore.
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[ Benjamin Poirier ]
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* tools/perf: Add python3 support to scripts (Closes: #944641)
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@ -1,104 +0,0 @@
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From: Paul Burton <paulburton@kernel.org>
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Date: Fri, 18 Oct 2019 15:38:48 -0700
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Subject: MIPS: tlbex: Fix build_restore_pagemask KScratch restore
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Origin: https://git.kernel.org/linus/b42aa3fd5957e4daf4b69129e5ce752a2a53e7d6
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build_restore_pagemask() will restore the value of register $1/$at when
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its restore_scratch argument is non-zero, and aims to do so by filling a
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branch delay slot. Commit 0b24cae4d535 ("MIPS: Add missing EHB in mtc0
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-> mfc0 sequence.") added an EHB instruction (Execution Hazard Barrier)
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prior to restoring $1 from a KScratch register, in order to resolve a
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hazard that can result in stale values of the KScratch register being
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observed. In particular, P-class CPUs from MIPS with out of order
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execution pipelines such as the P5600 & P6600 are affected.
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Unfortunately this EHB instruction was inserted in the branch delay slot
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causing the MFC0 instruction which performs the restoration to no longer
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execute along with the branch. The result is that the $1 register isn't
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actually restored, ie. the TLB refill exception handler clobbers it -
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which is exactly the problem the EHB is meant to avoid for the P-class
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CPUs.
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Similarly build_get_pgd_vmalloc() will restore the value of $1/$at when
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its mode argument equals refill_scratch, and suffers from the same
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problem.
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Fix this by in both cases moving the EHB earlier in the emitted code.
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There's no reason it needs to immediately precede the MFC0 - it simply
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needs to be between the MTC0 & MFC0.
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This bug only affects Cavium Octeon systems which use
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build_fast_tlb_refill_handler().
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Signed-off-by: Paul Burton <paulburton@kernel.org>
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Fixes: 0b24cae4d535 ("MIPS: Add missing EHB in mtc0 -> mfc0 sequence.")
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Cc: Dmitry Korotin <dkorotin@wavecomp.com>
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Cc: stable@vger.kernel.org # v3.15+
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Cc: linux-mips@vger.kernel.org
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Cc: linux-kernel@vger.kernel.org
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---
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arch/mips/mm/tlbex.c | 23 +++++++++++++++--------
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1 file changed, 15 insertions(+), 8 deletions(-)
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diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
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index e01cb33bfa1a..41bb91f05688 100644
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--- a/arch/mips/mm/tlbex.c
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+++ b/arch/mips/mm/tlbex.c
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@@ -653,6 +653,13 @@ static void build_restore_pagemask(u32 **p, struct uasm_reloc **r,
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int restore_scratch)
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{
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if (restore_scratch) {
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+ /*
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+ * Ensure the MFC0 below observes the value written to the
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+ * KScratch register by the prior MTC0.
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+ */
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+ if (scratch_reg >= 0)
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+ uasm_i_ehb(p);
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+
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/* Reset default page size */
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if (PM_DEFAULT_MASK >> 16) {
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uasm_i_lui(p, tmp, PM_DEFAULT_MASK >> 16);
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@@ -667,12 +674,10 @@ static void build_restore_pagemask(u32 **p, struct uasm_reloc **r,
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uasm_i_mtc0(p, 0, C0_PAGEMASK);
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uasm_il_b(p, r, lid);
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}
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- if (scratch_reg >= 0) {
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- uasm_i_ehb(p);
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+ if (scratch_reg >= 0)
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UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
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- } else {
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+ else
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UASM_i_LW(p, 1, scratchpad_offset(0), 0);
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- }
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} else {
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/* Reset default page size */
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if (PM_DEFAULT_MASK >> 16) {
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@@ -921,6 +926,10 @@ build_get_pgd_vmalloc64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
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}
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if (mode != not_refill && check_for_high_segbits) {
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uasm_l_large_segbits_fault(l, *p);
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+
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+ if (mode == refill_scratch && scratch_reg >= 0)
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+ uasm_i_ehb(p);
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+
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/*
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* We get here if we are an xsseg address, or if we are
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* an xuseg address above (PGDIR_SHIFT+PGDIR_BITS) boundary.
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@@ -939,12 +948,10 @@ build_get_pgd_vmalloc64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
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uasm_i_jr(p, ptr);
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if (mode == refill_scratch) {
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- if (scratch_reg >= 0) {
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- uasm_i_ehb(p);
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+ if (scratch_reg >= 0)
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UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
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- } else {
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+ else
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UASM_i_LW(p, 1, scratchpad_offset(0), 0);
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- }
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} else {
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uasm_i_nop(p);
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}
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--
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2.24.0
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@ -80,7 +80,6 @@ bugfix/arm/ARM-dts-sun8i-h3-add-sy8106a-to-orange-pi-plus.patch
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bugfix/arm64/arm64-dts-allwinner-a64-Enable-A64-timer-workaround.patch
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bugfix/mips/MIPS-Loongson-Introduce-and-use-loongson_llsc_mb.patch
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bugfix/powerpc/powerpc-vdso-make-vdso32-installation-conditional-in.patch
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bugfix/mips/MIPS-tlbex-Fix-build_restore_pagemask-KScratch-resto.patch
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# Arch features
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features/mips/MIPS-increase-MAX-PHYSMEM-BITS-on-Loongson-3-only.patch
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