[PATCH v5 10/21] arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding()

[Marc Zyngier]

__read_sysreg_by_encoding() is used by a bunch of cpufeature helpers,
which should take the feature override into account. Let's do that.

For a good measure (and because we are likely to need to further
down the line), make this helper available to the rest of the
non-modular kernel.

Code that needs to know the *real* features of a CPU can still
use read_sysreg_s(), and find the bare, ugly truth.

Signed-off-by: Marc Zyngier <m...@kernel.org>
Reviewed-by: Suzuki K Poulose <suzuki.poul...@arm.com>
Acked-by: David Brazdil <dbraz...@google.com>
---
 arch/arm64/include/asm/cpufeature.h |  1 +
 arch/arm64/kernel/cpufeature.c      | 15 +++++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h 
b/arch/arm64/include/asm/cpufeature.h
index fe469389068e..4179cfc8ed57 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -606,6 +606,7 @@ void __init setup_cpu_features(void);
 void check_local_cpu_capabilities(void);
 
 u64 read_sanitised_ftr_reg(u32 id);
+u64 __read_sysreg_by_encoding(u32 sys_id);
 
 static inline bool cpu_supports_mixed_endian_el0(void)
 {
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index cb58c7c991ef..4b84a1e1dc51 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1145,14 +1145,17 @@ u64 read_sanitised_ftr_reg(u32 id)
 EXPORT_SYMBOL_GPL(read_sanitised_ftr_reg);
 
 #define read_sysreg_case(r)    \
-       case r:         return read_sysreg_s(r)
+       case r:         val = read_sysreg_s(r); break;
 
 /*
  * __read_sysreg_by_encoding() - Used by a STARTING cpu before cpuinfo is 
populated.
  * Read the system register on the current CPU
  */
-static u64 __read_sysreg_by_encoding(u32 sys_id)
+u64 __read_sysreg_by_encoding(u32 sys_id)
 {
+       struct arm64_ftr_reg *regp;
+       u64 val;
+
        switch (sys_id) {
        read_sysreg_case(SYS_ID_PFR0_EL1);
        read_sysreg_case(SYS_ID_PFR1_EL1);
@@ -1195,6 +1198,14 @@ static u64 __read_sysreg_by_encoding(u32 sys_id)
                BUG();
                return 0;
        }
+
+       regp  = get_arm64_ftr_reg(sys_id);
+       if (regp) {
+               val &= ~regp->override->mask;
+               val |= (regp->override->val & regp->override->mask);
+       }
+
+       return val;
 }
 
 #include <linux/irqchip/arm-gic-v3.h>
-- 
2.29.2