arm64: cpufeature: Fix handling of CTR_EL0.IDC field

CTR_EL0.IDC reports the data cache clean requirements for instruction
to data coherence. However, if the field is 0, we need to check the
CLIDR_EL1 fields to detect the status of the feature. Currently we
don't do this and generate a warning with tainting the kernel, when
there is a mismatch in the field among the CPUs. Also the userspace
doesn't have a reliable way to check the CLIDR_EL1 register to check
the status.

This patch fixes the problem by checking the CLIDR_EL1 fields, when
(CTR_EL0.IDC == 0) and updates the kernel's copy of the CTR_EL0 for
the CPU with the actual status of the feature. This would allow the
sanity check infrastructure to do the proper checking of the fields
and also allow the CTR_EL0 emulation code to supply the real status
of the feature.

Now, if a CPU has raw CTR_EL0.IDC == 0 and effective IDC == 1 (with
overall system wide IDC == 1), we need to expose the real value to
the user. So, we trap CTR_EL0 access on the CPU which reports incorrect
CTR_EL0.IDC.

Fixes: commit 6ae4b6e057888 ("arm64: Add support for new control bits CTR_EL0.DIC and CTR_EL0.IDC")
Cc: Shanker Donthineni <shankerd@codeaurora.org>
Cc: Philip Elcan <pelcan@codeaurora.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/cache.h b/arch/arm64/include/asm/cache.h
index 5ee5bca8c24b..13dd42c3ad4e 100644
--- a/arch/arm64/include/asm/cache.h
+++ b/arch/arm64/include/asm/cache.h
@@ -40,6 +40,15 @@
 #define L1_CACHE_SHIFT		(6)
 #define L1_CACHE_BYTES		(1 << L1_CACHE_SHIFT)
 
+
+#define CLIDR_LOUU_SHIFT	27
+#define CLIDR_LOC_SHIFT		24
+#define CLIDR_LOUIS_SHIFT	21
+
+#define CLIDR_LOUU(clidr)	(((clidr) >> CLIDR_LOUU_SHIFT) & 0x7)
+#define CLIDR_LOC(clidr)	(((clidr) >> CLIDR_LOC_SHIFT) & 0x7)
+#define CLIDR_LOUIS(clidr)	(((clidr) >> CLIDR_LOUIS_SHIFT) & 0x7)
+
 /*
  * Memory returned by kmalloc() may be used for DMA, so we must make
  * sure that all such allocations are cache aligned. Otherwise,
@@ -84,6 +93,37 @@ static inline int cache_line_size(void)
 	return cwg ? 4 << cwg : ARCH_DMA_MINALIGN;
 }
 
+/*
+ * Read the effective value of CTR_EL0.
+ *
+ * According to ARM ARM for ARMv8-A (ARM DDI 0487C.a),
+ * section D10.2.33 "CTR_EL0, Cache Type Register" :
+ *
+ * CTR_EL0.IDC reports the data cache clean requirements for
+ * instruction to data coherence.
+ *
+ *  0 - dcache clean to PoU is required unless :
+ *     (CLIDR_EL1.LoC == 0) || (CLIDR_EL1.LoUIS == 0 && CLIDR_EL1.LoUU == 0)
+ *  1 - dcache clean to PoU is not required for i-to-d coherence.
+ *
+ * This routine provides the CTR_EL0 with the IDC field updated to the
+ * effective state.
+ */
+static inline u32 __attribute_const__ read_cpuid_effective_cachetype(void)
+{
+	u32 ctr = read_cpuid_cachetype();
+
+	if (!(ctr & BIT(CTR_IDC_SHIFT))) {
+		u64 clidr = read_sysreg(clidr_el1);
+
+		if (CLIDR_LOC(clidr) == 0 ||
+		    (CLIDR_LOUIS(clidr) == 0 && CLIDR_LOUU(clidr) == 0))
+			ctr |= BIT(CTR_IDC_SHIFT);
+	}
+
+	return ctr;
+}
+
 #endif	/* __ASSEMBLY__ */
 
 #endif