The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 0b24cae4d535045f4c9e177aa228d4e97bad212c Mon Sep 17 00:00:00 2001
From: Dmitry Korotin <dkorotin@xxxxxxxxxxxx>
Date: Mon, 24 Jun 2019 19:05:27 +0000
Subject: [PATCH] MIPS: Add missing EHB in mtc0 -> mfc0 sequence.
Add a missing EHB (Execution Hazard Barrier) in mtc0 -> mfc0 sequence.
Without this execution hazard barrier it's possible for the value read
back from the KScratch register to be the value from before the mtc0.
Reproducible on P5600 & P6600.
The hazard is documented in the MIPS Architecture Reference Manual Vol.
III: MIPS32/microMIPS32 Privileged Resource Architecture (MD00088), rev
6.03 table 8.1 which includes:
Producer | Consumer | Hazard
----------|----------|----------------------------
mtc0 | mfc0 | any coprocessor 0 register
Signed-off-by: Dmitry Korotin <dkorotin@xxxxxxxxxxxx>
[paul.burton@xxxxxxxx:
- Commit message tweaks.
- Add Fixes tags.
- Mark for stable back to v3.15 where P5600 support was introduced.]
Signed-off-by: Paul Burton <paul.burton@xxxxxxxx>
Fixes: 3d8bfdd03072 ("MIPS: Use C0_KScratch (if present) to hold PGD pointer.")
Fixes: 829dcc0a956a ("MIPS: Add MIPS P5600 probe support")
Cc: linux-mips@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # v3.15+
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 65b6e85447b1..144ceb0fba88 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -391,6 +391,7 @@ static struct work_registers build_get_work_registers(u32 **p)
static void build_restore_work_registers(u32 **p)
{
if (scratch_reg >= 0) {
+ uasm_i_ehb(p);
UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
return;
}
@@ -668,10 +669,12 @@ static void build_restore_pagemask(u32 **p, struct uasm_reloc **r,
uasm_i_mtc0(p, 0, C0_PAGEMASK);
uasm_il_b(p, r, lid);
}
- if (scratch_reg >= 0)
+ if (scratch_reg >= 0) {
+ uasm_i_ehb(p);
UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
- else
+ } else {
UASM_i_LW(p, 1, scratchpad_offset(0), 0);
+ }
} else {
/* Reset default page size */
if (PM_DEFAULT_MASK >> 16) {
@@ -938,10 +941,12 @@ build_get_pgd_vmalloc64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
uasm_i_jr(p, ptr);
if (mode == refill_scratch) {
- if (scratch_reg >= 0)
+ if (scratch_reg >= 0) {
+ uasm_i_ehb(p);
UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
- else
+ } else {
UASM_i_LW(p, 1, scratchpad_offset(0), 0);
+ }
} else {
uasm_i_nop(p);
}
@@ -1258,6 +1263,7 @@ build_fast_tlb_refill_handler (u32 **p, struct uasm_label **l,
UASM_i_MTC0(p, odd, C0_ENTRYLO1); /* load it */
if (c0_scratch_reg >= 0) {
+ uasm_i_ehb(p);
UASM_i_MFC0(p, scratch, c0_kscratch(), c0_scratch_reg);
build_tlb_write_entry(p, l, r, tlb_random);
uasm_l_leave(l, *p);
@@ -1603,15 +1609,17 @@ static void build_setup_pgd(void)
uasm_i_dinsm(&p, a0, 0, 29, 64 - 29);
uasm_l_tlbl_goaround1(&l, p);
UASM_i_SLL(&p, a0, a0, 11);
- uasm_i_jr(&p, 31);
UASM_i_MTC0(&p, a0, C0_CONTEXT);
+ uasm_i_jr(&p, 31);
+ uasm_i_ehb(&p);
} else {
/* PGD in c0_KScratch */
- uasm_i_jr(&p, 31);
if (cpu_has_ldpte)
UASM_i_MTC0(&p, a0, C0_PWBASE);
else
UASM_i_MTC0(&p, a0, c0_kscratch(), pgd_reg);
+ uasm_i_jr(&p, 31);
+ uasm_i_ehb(&p);
}
#else
#ifdef CONFIG_SMP
@@ -1625,13 +1633,16 @@ static void build_setup_pgd(void)
UASM_i_LA_mostly(&p, a2, pgdc);
UASM_i_SW(&p, a0, uasm_rel_lo(pgdc), a2);
#endif /* SMP */
- uasm_i_jr(&p, 31);
/* if pgd_reg is allocated, save PGD also to scratch register */
- if (pgd_reg != -1)
+ if (pgd_reg != -1) {
UASM_i_MTC0(&p, a0, c0_kscratch(), pgd_reg);
- else
+ uasm_i_jr(&p, 31);
+ uasm_i_ehb(&p);
+ } else {
+ uasm_i_jr(&p, 31);
uasm_i_nop(&p);
+ }
#endif
if (p >= (u32 *)tlbmiss_handler_setup_pgd_end)
panic("tlbmiss_handler_setup_pgd space exceeded");
