arm64: Work around Falkor erratum 1003

The Qualcomm Datacenter Technologies Falkor v1 CPU may allocate TLB entries
using an incorrect ASID when TTBRx_EL1 is being updated. When the erratum
is triggered, page table entries using the new translation table base
address (BADDR) will be allocated into the TLB using the old ASID. All
circumstances leading to the incorrect ASID being cached in the TLB arise
when software writes TTBRx_EL1[ASID] and TTBRx_EL1[BADDR], a memory
operation is in the process of performing a translation using the specific
TTBRx_EL1 being written, and the memory operation uses a translation table
descriptor designated as non-global. EL2 and EL3 code changing the EL1&0
ASID is not subject to this erratum because hardware is prohibited from
performing translations from an out-of-context translation regime.

Consider the following pseudo code.

  write new BADDR and ASID values to TTBRx_EL1

Replacing the above sequence with the one below will ensure that no TLB
entries with an incorrect ASID are used by software.

  write reserved value to TTBRx_EL1[ASID]
  ISB
  write new value to TTBRx_EL1[BADDR]
  ISB
  write new value to TTBRx_EL1[ASID]
  ISB

When the above sequence is used, page table entries using the new BADDR
value may still be incorrectly allocated into the TLB using the reserved
ASID. Yet this will not reduce functionality, since TLB entries incorrectly
tagged with the reserved ASID will never be hit by a later instruction.

Based on work by Shanker Donthineni <shankerd@codeaurora.org>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

3 files changed, 32 insertions, 2 deletions

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 446f6c46d4b1..33b20c075fb3 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -25,6 +25,7 @@
 
 #include <asm/asm-offsets.h>
 #include <asm/cpufeature.h>
+#include <asm/mmu_context.h>
 #include <asm/page.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/ptrace.h>
@@ -423,6 +424,28 @@ alternative_endif
 	.endm
 
 /*
+ * Errata workaround prior to TTBR0_EL1 update
+ *
+ * 	val:	TTBR value with new BADDR, preserved
+ * 	tmp0:	temporary register, clobbered
+ * 	tmp1:	other temporary register, clobbered
+ */
+	.macro	pre_ttbr0_update_workaround, val, tmp0, tmp1
+#ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003
+alternative_if ARM64_WORKAROUND_QCOM_FALKOR_E1003
+	mrs	\tmp0, ttbr0_el1
+	mov	\tmp1, #FALKOR_RESERVED_ASID
+	bfi	\tmp0, \tmp1, #48, #16		// reserved ASID + old BADDR
+	msr	ttbr0_el1, \tmp0
+	isb
+	bfi	\tmp0, \val, #0, #48		// reserved ASID + new BADDR
+	msr	ttbr0_el1, \tmp0
+	isb
+alternative_else_nop_endif
+#endif
+	.endm
+
+/*
  * Errata workaround post TTBR0_EL1 update.
  */
 	.macro	post_ttbr0_update_workaround
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index d1207ac696ac..fb78a5d3b60b 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -36,7 +36,8 @@
 #define ARM64_MISMATCHED_CACHE_LINE_SIZE	15
 #define ARM64_HAS_NO_FPSIMD			16
 #define ARM64_WORKAROUND_REPEAT_TLBI		17
+#define ARM64_WORKAROUND_QCOM_FALKOR_E1003	18
 
-#define ARM64_NCAPS				18
+#define ARM64_NCAPS				19
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 63e9982daca1..1ef40d82cfd3 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -19,6 +19,10 @@
 #ifndef __ASM_MMU_CONTEXT_H
 #define __ASM_MMU_CONTEXT_H
 
+#define FALKOR_RESERVED_ASID	1
+
+#ifndef __ASSEMBLY__
+
 #include <linux/compiler.h>
 #include <linux/sched.h>
 
@@ -220,4 +224,6 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
 
 void verify_cpu_asid_bits(void);
 
-#endif
+#endif /* !__ASSEMBLY__ */
+
+#endif /* !__ASM_MMU_CONTEXT_H */