From: Marc Zyngier <marc.zyngier@arm.com>
Date: Mon, 15 Apr 2019 13:03:51 +0100
Subject: arm64: Restrict ARM64_ERRATUM_1188873 mitigation to AArch32
Git-commit: 0f80cad3124f986d0e46c14d46b8da06d87a2bf4
Patch-mainline: v5.2-rc1
References: jsc#ECO-561
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>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
arch/arm64/kernel/entry.S | 19 +++++++++++++++++--
drivers/clocksource/arm_arch_timer.c | 15 ---------------
2 files changed, 17 insertions(+), 17 deletions(-)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -330,6 +330,21 @@ 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, 5f, x0, x1
5:
.endif
@@ -357,11 +372,11 @@ 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
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -318,13 +318,6 @@ static u64 notrace arm64_858921_read_cnt
}
#endif
-#ifdef CONFIG_ARM64_ERRATUM_1188873
-static u64 notrace arm64_1188873_read_cntvct_el0(void)
-{
- return read_sysreg(cntvct_el0);
-}
-#endif
-
#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *,
timer_unstable_counter_workaround);
@@ -415,14 +408,6 @@ static const struct arch_timer_erratum_w
.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
};
typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,