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arm64: Rework ARM_ERRATUM_1414080 handling

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The current handling of erratum 1414080 has the side effect that
cntkctl_el1 can get changed for both 32 and 64bit tasks.

This isn't a problem so far, but if we ever need to mitigate another
of these errata on the 64bit side, we'd better keep the messing with
cntkctl_el1 local to 32bit tasks.

For that, make sure that on entering the kernel from a 32bit tasks,
userspace access to cntvct gets enabled, and disabled returning to
userspace, while it never gets changed for 64bit tasks.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20200706163802.1836732-5-maz@kernel.org
[will: removed branch instructions per Mark's review comments]
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Marc Zyngier 2020-07-06 17:38:02 +01:00 committed by Will Deacon
parent 4b661d6133
commit dc802f2bc0
1 changed files with 19 additions and 15 deletions
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34
arch/arm64/kernel/entry.S
View file

@ -167,6 +167,17 @@ alternative_cb_end
stp x28, x29, [sp, #16 * 14]
.if \el == 0
.if \regsize == 32
// If we're returning from a 32-bit task on a system affected by
// 1418040 then re-enable userspace access to the virtual counter.
#ifdef CONFIG_ARM64_ERRATUM_1418040
alternative_if ARM64_WORKAROUND_1418040
mrs x0, cntkctl_el1
orr x0, x0, #2 // ARCH_TIMER_USR_VCT_ACCESS_EN
msr cntkctl_el1, x0
alternative_else_nop_endif
#endif
.endif
clear_gp_regs
mrs x21, sp_el0
ldr_this_cpu tsk, __entry_task, x20
@ -320,6 +331,14 @@ alternative_else_nop_endif
tst x22, #PSR_MODE32_BIT // native task?
b.eq 3f
#ifdef CONFIG_ARM64_ERRATUM_1418040
alternative_if ARM64_WORKAROUND_1418040
mrs x0, cntkctl_el1
bic x0, x0, #2 // ARCH_TIMER_USR_VCT_ACCESS_EN
msr cntkctl_el1, x0
alternative_else_nop_endif
#endif
#ifdef CONFIG_ARM64_ERRATUM_845719
alternative_if ARM64_WORKAROUND_845719
#ifdef CONFIG_PID_IN_CONTEXTIDR
@ -331,21 +350,6 @@ alternative_if ARM64_WORKAROUND_845719
alternative_else_nop_endif
#endif
3:
#ifdef CONFIG_ARM64_ERRATUM_1418040
alternative_if_not ARM64_WORKAROUND_1418040
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
scs_save tsk, x0
/* No kernel C function calls after this as user keys are set. */