[PATCH v3 04/20] arm64: mm: Remove pre_ttbr0_update_workaround for Falkor erratum #E1003

[Will Deacon]

The pre_ttbr0_update_workaround hook is called prior to context-switching
TTBR0 because Falkor erratum E1003 can cause TLB allocation with the wrong
ASID if both the ASID and the base address of the TTBR are updated at
the same time.

With the ASID sitting safely in TTBR1, we no longer update things
atomically, so we can remove the pre_ttbr0_update_workaround macro as
it's no longer required. The erratum infrastructure and documentation
is left around for #E1003, as it will be required by the entry
trampoline code in a future patch.

Reviewed-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
---
 arch/arm64/include/asm/assembler.h   | 22 ----------------------
 arch/arm64/include/asm/mmu_context.h |  2 --
 arch/arm64/mm/context.c              | 11 -----------
 arch/arm64/mm/proc.S                 |  1 -
 4 files changed, 36 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index aef72d886677..e1fa5db858b7 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -26,7 +26,6 @@
 #include <asm/asm-offsets.h>
 #include <asm/cpufeature.h>
 #include <asm/debug-monitors.h>
-#include <asm/mmu_context.h>
 #include <asm/page.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/ptrace.h>
@@ -478,27 +477,6 @@ 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.
  */
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 2d63611e4311..f9744944cf12 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -19,8 +19,6 @@
 #ifndef __ASM_MMU_CONTEXT_H
 #define __ASM_MMU_CONTEXT_H
 
-#define FALKOR_RESERVED_ASID	1
-
 #ifndef __ASSEMBLY__
 
 #include <linux/compiler.h>
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index 6f4017046323..78a2dc596fee 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -79,13 +79,6 @@ void verify_cpu_asid_bits(void)
 	}
 }
 
-static void set_reserved_asid_bits(void)
-{
-	if (IS_ENABLED(CONFIG_QCOM_FALKOR_ERRATUM_1003) &&
-	    cpus_have_const_cap(ARM64_WORKAROUND_QCOM_FALKOR_E1003))
-		__set_bit(FALKOR_RESERVED_ASID, asid_map);
-}
-
 static void flush_context(unsigned int cpu)
 {
 	int i;
@@ -94,8 +87,6 @@ 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);
 
-	set_reserved_asid_bits();
-
 	for_each_possible_cpu(i) {
 		asid = atomic64_xchg_relaxed(&per_cpu(active_asids, i), 0);
 		/*
@@ -254,8 +245,6 @@ static int asids_init(void)
 		panic("Failed to allocate bitmap for %lu ASIDs\n",
 		      NUM_USER_ASIDS);
 
-	set_reserved_asid_bits();
-
 	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 a8a64898a2aa..f2ff0837577c 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -138,7 +138,6 @@ ENDPROC(cpu_do_resume)
  *	- pgd_phys - physical address of new TTB
  */
 ENTRY(cpu_do_switch_mm)
-	pre_ttbr0_update_workaround x0, x2, x3
 	mrs	x2, ttbr1_el1
 	mmid	x1, x1				// get mm->context.id
 	bfi	x2, x1, #48, #16		// set the ASID
-- 
2.1.4