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arm64: Restrict ARM64_ERRATUM_1188873 mitigation to AArch32 

We currently deal with ARM64_ERRATUM_1188873 by always trapping EL0
accesses for both instruction sets. Although nothing wrong comes out
of that, people trying to squeeze the last drop of performance from
buggy HW find this over the top. Oh well.

Let's change the mitigation by flipping the counter enable bit
on return to userspace. Non-broken HW gets an extra branch on
the fast path, which is hopefully not the end of the world.
The arch timer workaround is also removed.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Marc Zyngier 2019-04-15 13:03:51 +01:00 committed by Will Deacon
parent 79a3aaa7b8
commit 0f80cad312
2 changed files with 17 additions and 17 deletions
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19
arch/arm64/kernel/entry.S
View File

@ -336,6 +336,21 @@ alternative_if ARM64_WORKAROUND_845719
alternative_else_nop_endif
#endif
3:
#ifdef CONFIG_ARM64_ERRATUM_1188873
alternative_if_not ARM64_WORKAROUND_1188873
b 4f
alternative_else_nop_endif
/*
* if (x22.mode32 == cntkctl_el1.el0vcten)
* cntkctl_el1.el0vcten = ~cntkctl_el1.el0vcten
*/
mrs x1, cntkctl_el1
eon x0, x1, x22, lsr #3
tbz x0, #1, 4f
eor x1, x1, #2 // ARCH_TIMER_USR_VCT_ACCESS_EN
msr cntkctl_el1, x1
4:
#endif
apply_ssbd 0, x0, x1
.endif
@ -362,11 +377,11 @@ alternative_else_nop_endif
.if \el == 0
alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
bne 4f
bne 5f
msr far_el1, x30
tramp_alias x30, tramp_exit_native
br x30
4:
5:
tramp_alias x30, tramp_exit_compat
br x30
#endif

15
drivers/clocksource/arm_arch_timer.c
View File

@ -319,13 +319,6 @@ static u64 notrace arm64_858921_read_cntvct_el0(void)
}
#endif
#ifdef CONFIG_ARM64_ERRATUM_1188873
static u64 notrace arm64_1188873_read_cntvct_el0(void)
{
return read_sysreg(cntvct_el0);
}
#endif
#ifdef CONFIG_SUN50I_ERRATUM_UNKNOWN1
/*
* The low bits of the counter registers are indeterminate while bit 10 or
@ -457,14 +450,6 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
.read_cntvct_el0 = arm64_858921_read_cntvct_el0,
},
#endif
#ifdef CONFIG_ARM64_ERRATUM_1188873
{
.match_type = ate_match_local_cap_id,
.id = (void *)ARM64_WORKAROUND_1188873,
.desc = "ARM erratum 1188873",
.read_cntvct_el0 = arm64_1188873_read_cntvct_el0,
},
#endif
#ifdef CONFIG_SUN50I_ERRATUM_UNKNOWN1
{
.match_type = ate_match_dt,