[PATCH 2/3] arm64: Work around Falkor erratum 1003

Christopher Covington
2016-12-07T20:01:16Z

From: Shanker Donthineni <shankerd@codeaurora.org>

On the Qualcomm Datacenter Technologies Falkor v1 CPU, memory accesses may
allocate TLB entries using an incorrect ASID when TTBRx_EL1 is being
updated. Changing the TTBRx_EL1[ASID] and TTBRx_EL1[BADDR] fields
separately using a reserved ASID will ensure that there are no TLB entries
with incorrect ASID after changing the the ASID.

Pseudo code:
write TTBRx_EL1[ASID] to a reserved value
ISB
write TTBRx_EL1[BADDR] to a desired value
ISB
write TTBRx_EL1[ASID] to a desired value
ISB

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Christopher Covington <cov@codeaurora.org>
---
arch/arm64/Kconfig | 11 +++++++++++
arch/arm64/include/asm/cpucaps.h | 3 ++-
arch/arm64/kernel/cpu_errata.c | 7 +++++++
arch/arm64/mm/context.c | 10 ++++++++++
arch/arm64/mm/proc.S | 21 +++++++++++++++++++++
5 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 969ef88..1004a3d 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -474,6 +474,17 @@ config CAVIUM_ERRATUM_27456

If unsure, say Y.

+config QCOM_FALKOR_ERRATUM_E1003
+ bool "Falkor E1003: Incorrect translation due to ASID change"
+ default y
+ help
+ An incorrect translation TLBI entry may be created while
+ changing the ASID & translation table address together for
+ TTBR0_EL1. The workaround for this issue is use a reserved
+ ASID in cpu_do_switch_mm() before switching to target ASID.
+
+ If unsure, say Y.
+
endmenu

diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 87b4465..cb6a8c2 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -34,7 +34,8 @@
#define ARM64_HAS_32BIT_EL0 13
#define ARM64_HYP_OFFSET_LOW 14
#define ARM64_MISMATCHED_CACHE_LINE_SIZE 15
+#define ARM64_WORKAROUND_QCOM_FALKOR_E1003 16

-#define ARM64_NCAPS 16
+#define ARM64_NCAPS 17

#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index b75e917..3789e2f 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -130,6 +130,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
.def_scope = SCOPE_LOCAL_CPU,
.enable = cpu_enable_trap_ctr_access,
},
+#ifdef CONFIG_QCOM_FALKOR_ERRATUM_E1003
+ {
+ .desc = "Qualcomm Falkor erratum E1003",
+ .capability = ARM64_WORKAROUND_QCOM_FALKOR_E1003,
+ MIDR_RANGE(MIDR_QCOM_FALKOR_V1, 0x00, 0x00),
+ },
+#endif
{
}
};
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index efcf1f7..f8d94ff 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -87,6 +87,11 @@ static void flush_context(unsigned int cpu)
/* Update the list of reserved ASIDs and the ASID bitmap. */
bitmap_clear(asid_map, 0, NUM_USER_ASIDS);

+ /* Reserve ASID '1' for Falkor erratum E1003 */
+ if (IS_ENABLED(CONFIG_QCOM_FALKOR_ERRATUM_E1003) &&
+ cpus_have_cap(ARM64_WORKAROUND_QCOM_FALKOR_E1003))
+ __set_bit(1, asid_map);
+
/*
* Ensure the generation bump is observed before we xchg the
* active_asids.
@@ -239,6 +244,11 @@ static int asids_init(void)
panic("Failed to allocate bitmap for %lu ASIDs\n",
NUM_USER_ASIDS);

+ /* Reserve ASID '1' for Falkor erratum E1003 */
+ if (IS_ENABLED(CONFIG_QCOM_FALKOR_ERRATUM_E1003) &&
+ cpus_have_cap(ARM64_WORKAROUND_QCOM_FALKOR_E1003))
+ __set_bit(1, asid_map);
+
pr_info("ASID allocator initialised with %lu entries\n", NUM_USER_ASIDS);
return 0;
}
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 352c73b..b4d6508 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -134,6 +134,27 @@ ENDPROC(cpu_do_resume)
ENTRY(cpu_do_switch_mm)
mmid x1, x1 // get mm->context.id
bfi x0, x1, #48, #16 // set the ASID
+#ifdef CONFIG_QCOM_FALKOR_ERRATUM_E1003
+alternative_if_not ARM64_WORKAROUND_QCOM_FALKOR_E1003
+ nop
+ nop
+ nop
+ nop
+ nop
+ nop
+ nop
+ nop
+alternative_else
+ mrs x2, ttbr0_el1 // get cuurent TTBR0_EL1
+ mov x3, #1 // reserved ASID
+ bfi x2, x3, #48, #16 // set the reserved ASID + old BADDR
+ msr ttbr0_el1, x2 // update TTBR0_EL1
+ isb
+ bfi x2, x0, #0, #48 // set the desired BADDR + reserved ASID
+ msr ttbr0_el1, x2 // update TTBR0_EL1
+ isb
+alternative_endif
+#endif
msr ttbr0_el1, x0 // set TTBR0
isb
alternative_if ARM64_WORKAROUND_CAVIUM_27456
--
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora
Forum, a Linux Foundation Collaborative Project.