[PATCH v7 11/23] arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding()

Marc Zyngier
2021-02-08T10:18:57Z

__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 <maz@kernel.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: David Brazdil <dbrazdil@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.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 b1f53147e2b2..b5bf7af68691 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 a4e5c619a516..97da9ed4b79d 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1148,14 +1148,17 @@ 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);
@@ -1198,6 +1201,14 @@ 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