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

From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	David Brazdil <dbrazdil@google.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Jing Zhang <jingzhangos@google.com>,
	Ajay Patil <pajay@qti.qualcomm.com>,
	Prasad Sodagudi <psodagud@codeaurora.org>,
	Srinivas Ramana <sramana@codeaurora.org>,
	Hector Martin <marcan@marcan.st>,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	kernel-team@android.com
Subject: [PATCH v7 11/23] arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding()
Date: Mon,  8 Feb 2021 09:57:20 +0000	[thread overview]
Message-ID: <20210208095732.3267263-12-maz@kernel.org> (raw)
In-Reply-To: <20210208095732.3267263-1-maz@kernel.org>

__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

