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

From: [email-masked] (Christopher Covington)
Date: Wed, 7 Dec 2016 15:00:26 -0500

From: Shanker Donthineni <[email-masked]>

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 <[email-masked]>
Signed-off-by: Christopher Covington <[email-masked]>
---
 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
-- 
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Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora
Forum, a Linux Foundation Collaborative Project.