[Xen-devel] [PATCH v2 3/6] xen/arm: Use check_workaround to handle the erratum 766422

[Julien Grall <julien.grall@xxxxxxx>]

Currently, Xen is accessing the stored MIDR everytime it has to check
whether the processor is affected by the erratum 766422.

This could take advantage of the new capability bitfields to detect
whether the processor is affected at boot time.

With this patch, the number of instructions to check the erratum is
going down from ~13 (including 2 loads and a co-processor access) to
~6 instructions (include 1 load).

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

---
    Changes in v2:
        - Update the commit message
---
 xen/arch/arm/cpuerrata.c              | 6 ++++++
 xen/arch/arm/traps.c                  | 3 ++-
 xen/include/asm-arm/arm32/processor.h | 4 ----
 xen/include/asm-arm/arm64/processor.h | 2 --
 xen/include/asm-arm/cpuerrata.h       | 2 ++
 xen/include/asm-arm/cpufeature.h      | 3 ++-
 xen/include/asm-arm/processor.h       | 2 ++
 7 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
index 3ac97b3..748e02e 100644
--- a/xen/arch/arm/cpuerrata.c
+++ b/xen/arch/arm/cpuerrata.c
@@ -17,6 +17,12 @@ is_affected_midr_range(const struct arm_cpu_capabilities 
*entry)
 }
 
 static const struct arm_cpu_capabilities arm_errata[] = {
+    {
+        /* Cortex-A15 r0p4 */
+        .desc = "ARM erratum 766422",
+        .capability = ARM32_WORKAROUND_766422,
+        MIDR_RANGE(MIDR_CORTEX_A15, 0x04, 0x04),
+    },
 #if defined(CONFIG_ARM64_ERRATUM_827319) || \
     defined(CONFIG_ARM64_ERRATUM_824069)
     {
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index b34c46f..28982a4 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -46,6 +46,7 @@
 #include "vtimer.h"
 #include <asm/gic.h>
 #include <asm/vgic.h>
+#include <asm/cpuerrata.h>
 
 /* The base of the stack must always be double-word aligned, which means
  * that both the kernel half of struct cpu_user_regs (which is pushed in
@@ -2481,7 +2482,7 @@ static void do_trap_data_abort_guest(struct cpu_user_regs 
*regs,
      * Erratum 766422: Thumb store translation fault to Hypervisor may
      * not have correct HSR Rt value.
      */
-    if ( cpu_has_erratum_766422() && (regs->cpsr & PSR_THUMB) && dabt.write )
+    if ( check_workaround_766422() && (regs->cpsr & PSR_THUMB) && dabt.write )
     {
         rc = decode_instruction(regs, &info.dabt);
         if ( rc )
diff --git a/xen/include/asm-arm/arm32/processor.h 
b/xen/include/asm-arm/arm32/processor.h
index f41644d..11366bb 100644
--- a/xen/include/asm-arm/arm32/processor.h
+++ b/xen/include/asm-arm/arm32/processor.h
@@ -115,10 +115,6 @@ struct cpu_user_regs
 #define READ_SYSREG(R...)       READ_SYSREG32(R)
 #define WRITE_SYSREG(V, R...)   WRITE_SYSREG32(V, R)
 
-/* Erratum 766422: only Cortex A15 r0p4 is affected */
-#define cpu_has_erratum_766422()                             \
-    (unlikely(current_cpu_data.midr.bits == 0x410fc0f4))
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* __ASM_ARM_ARM32_PROCESSOR_H */
diff --git a/xen/include/asm-arm/arm64/processor.h 
b/xen/include/asm-arm/arm64/processor.h
index fef35a5..b0726ff 100644
--- a/xen/include/asm-arm/arm64/processor.h
+++ b/xen/include/asm-arm/arm64/processor.h
@@ -111,8 +111,6 @@ struct cpu_user_regs
 #define READ_SYSREG(name)     READ_SYSREG64(name)
 #define WRITE_SYSREG(v, name) WRITE_SYSREG64(v, name)
 
-#define cpu_has_erratum_766422() 0
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* __ASM_ARM_ARM64_PROCESSOR_H */
diff --git a/xen/include/asm-arm/cpuerrata.h b/xen/include/asm-arm/cpuerrata.h
index 2982a92..5880e77 100644
--- a/xen/include/asm-arm/cpuerrata.h
+++ b/xen/include/asm-arm/cpuerrata.h
@@ -40,6 +40,8 @@ static inline bool_t check_workaround_##erratum(void)         
  \
 
 #endif
 
+CHECK_WORKAROUND_HELPER(766422, ARM32_WORKAROUND_766422, CONFIG_ARM_32)
+
 #undef CHECK_WORKAROUND_HELPER
 
 #endif /* __ARM_CPUERRATA_H__ */
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index 78e2263..ac6eaf0 100644
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -37,8 +37,9 @@
 
 #define ARM64_WORKAROUND_CLEAN_CACHE    0
 #define ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE    1
+#define ARM32_WORKAROUND_766422 2
 
-#define ARM_NCAPS           2
+#define ARM_NCAPS           3
 
 #ifndef __ASSEMBLY__
 
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index 1708253..15bf890 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -46,9 +46,11 @@
 
 #define ARM_CPU_IMP_ARM             0x41
 
+#define ARM_CPU_PART_CORTEX_A15     0xC0F
 #define ARM_CPU_PART_CORTEX_A53     0xD03
 #define ARM_CPU_PART_CORTEX_A57     0xD07
 
+#define MIDR_CORTEX_A15 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, 
ARM_CPU_PART_CORTEX_A15)
 #define MIDR_CORTEX_A53 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, 
ARM_CPU_PART_CORTEX_A53)
 #define MIDR_CORTEX_A57 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, 
ARM_CPU_PART_CORTEX_A57)
 
-- 
1.9.1


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