[PATCH v2 2/5] arm64: Work around Falkor erratum 1003

From: Christopher Covington
Date: Thu Dec 29 2016 - 17:44:08 EST

From: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx>
Signed-off-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
---
Documentation/arm64/silicon-errata.txt | 43 +++++++++++++++++-----------------
arch/arm64/Kconfig | 16 +++++++++++++
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 | 12 ++++++++++
6 files changed, 69 insertions(+), 22 deletions(-)

diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
index 405da11..7151aed 100644
--- a/Documentation/arm64/silicon-errata.txt
+++ b/Documentation/arm64/silicon-errata.txt
@@ -42,24 +42,25 @@ file acts as a registry of software workarounds in the Linux Kernel and
will be updated when new workarounds are committed and backported to
stable kernels.

-| Implementor | Component | Erratum ID | Kconfig |
-+----------------+-----------------+-----------------+-------------------------+
-| ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
-| ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
-| ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
-| ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472 |
-| ARM | Cortex-A53 | #845719 | ARM64_ERRATUM_845719 |
-| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419 |
-| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
-| ARM | Cortex-A57 | #852523 | N/A |
-| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
-| ARM | Cortex-A72 | #853709 | N/A |
-| ARM | MMU-500 | #841119,#826419 | N/A |
-| | | | |
-| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
-| Cavium | ThunderX ITS | #23144 | CAVIUM_ERRATUM_23144 |
-| Cavium | ThunderX GICv3 | #23154 | CAVIUM_ERRATUM_23154 |
-| Cavium | ThunderX Core | #27456 | CAVIUM_ERRATUM_27456 |
-| Cavium | ThunderX SMMUv2 | #27704 | N/A |
-| | | | |
-| Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
+| Implementor | Component | Erratum ID | Kconfig |
++---------------+-----------------+-----------------+--------------------------+
+| ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
+| ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
+| ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
+| ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472 |
+| ARM | Cortex-A53 | #845719 | ARM64_ERRATUM_845719 |
+| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419 |
+| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
+| ARM | Cortex-A57 | #852523 | N/A |
+| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
+| ARM | Cortex-A72 | #853709 | N/A |
+| ARM | MMU-500 | #841119,#826419 | N/A |
+| | | | |
+| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
+| Cavium | ThunderX ITS | #23144 | CAVIUM_ERRATUM_23144 |
+| Cavium | ThunderX GICv3 | #23154 | CAVIUM_ERRATUM_23154 |
+| Cavium | ThunderX Core | #27456 | CAVIUM_ERRATUM_27456 |
+| Cavium | ThunderX SMMUv2 | #27704 | N/A |
+| | | | |
+| Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
+| Qualcomm | Falkor v1 | E1003 | QCOM_FALKOR_ERRATUM_1003 |
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1117421..7ce4a4b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -479,6 +479,22 @@ config CAVIUM_ERRATUM_27456

If unsure, say Y.

+config QCOM_FALKOR_ERRATUM_1003
+ 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.
+
+config QCOM_FALKOR_E1003_RESERVED_ASID
+ int
+ default 1
+ depends on QCOM_FALKOR_ERRATUM_1003
+
endmenu


diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 4174f09..5aaf7ee 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -35,7 +35,8 @@
#define ARM64_HYP_OFFSET_LOW 14
#define ARM64_MISMATCHED_CACHE_LINE_SIZE 15
#define ARM64_HAS_NO_FPSIMD 16
+#define ARM64_WORKAROUND_QCOM_FALKOR_E1003 17

-#define ARM64_NCAPS 17
+#define ARM64_NCAPS 18

#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index b75e917..787b542 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_1003
+ {
+ .desc = "Qualcomm Falkor erratum 1003",
+ .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 4c63cb1..9514a89 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 for Falkor erratum 1003 */
+ if (IS_ENABLED(CONFIG_QCOM_FALKOR_ERRATUM_1003) &&
+ cpus_have_cap(ARM64_WORKAROUND_QCOM_FALKOR_E1003))
+ __set_bit(CONFIG_QCOM_FALKOR_E1003_RESERVED_ASID, asid_map);
+
/*
* Ensure the generation bump is observed before we xchg the
* active_asids.
@@ -244,6 +249,11 @@ static int asids_init(void)
panic("Failed to allocate bitmap for %lu ASIDs\n",
NUM_USER_ASIDS);

+ /* Reserve ASID for Falkor erratum 1003 */
+ if (IS_ENABLED(CONFIG_QCOM_FALKOR_ERRATUM_1003) &&
+ cpus_have_cap(ARM64_WORKAROUND_QCOM_FALKOR_E1003))
+ __set_bit(CONFIG_QCOM_FALKOR_E1003_RESERVED_ASID, 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 32682be..0c6d173 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -140,6 +140,18 @@ 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_1003
+alternative_if ARM64_WORKAROUND_QCOM_FALKOR_E1003
+ mrs x2, ttbr0_el1 // get cuurent TTBR0_EL1
+ mov x3, #CONFIG_QCOM_FALKOR_ERRATUM_1003 // 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_else_nop_endif
+#endif
msr ttbr0_el1, x0 // set TTBR0
isb
post_ttbr0_update_workaround
--
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Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora
Forum, a Linux Foundation Collaborative Project.