[RFC PATCH 5/7] arm64: mm: Add pgprot_pbha() to allow drivers to request PBHA values

[James Morse]

Add a pgprot_pbha() helper that modifies a pgprot_t to include a pbha
value. The value is checked against those that were listed as only
affecting performance.

Signed-off-by: James Morse <james.morse at arm.com>
---
 arch/arm64/include/asm/pgtable-hwdef.h |  1 +
 arch/arm64/include/asm/pgtable.h       | 12 ++++++++++++
 arch/arm64/kernel/cpufeature.c         |  1 +
 3 files changed, 14 insertions(+)

diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index 3d41242c52b0..bef11fb9a255 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -154,6 +154,7 @@
 #define PTE_CONT		(_AT(pteval_t, 1) << 52)	/* Contiguous range */
 #define PTE_PXN			(_AT(pteval_t, 1) << 53)	/* Privileged XN */
 #define PTE_UXN			(_AT(pteval_t, 1) << 54)	/* User XN */
+#define PTE_PBHA_MASK		(_AT(pteval_t, 0xf) << 59)	/* Page Base Hardware Attributes */
 
 #define PTE_ADDR_LOW		(((_AT(pteval_t, 1) << (48 - PAGE_SHIFT)) - 1) << PAGE_SHIFT)
 #ifdef CONFIG_ARM64_PA_BITS_52
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index dfa76afa0ccf..3bc242db2c3c 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -518,6 +518,18 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
 	__pgprot_modify(prot, PTE_ATTRINDX_MASK, \
 			PTE_ATTRINDX(MT_NORMAL_NC) | PTE_PXN | PTE_UXN)
 
+
+extern unsigned long arm64_pbha_perf_only_values;
+static inline unsigned long __pbha_check_perf_only(unsigned long pbha_val)
+{
+	if (test_bit(pbha_val, &arm64_pbha_perf_only_values))
+		return FIELD_PREP(PTE_PBHA_MASK, pbha_val);
+	return 0;
+}
+
+#define pgprot_pbha(prot, pbha_val) \
+	__pgprot_modify(prot, PTE_PBHA_MASK, __pbha_check_perf_only(pbha_val))
+
 #define __HAVE_PHYS_MEM_ACCESS_PROT
 struct file;
 extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 548c6f96a878..88f0f805b938 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -112,6 +112,7 @@ bool arm64_use_ng_mappings = false;
 EXPORT_SYMBOL(arm64_use_ng_mappings);
 
 unsigned long __ro_after_init arm64_pbha_perf_only_values;
+EXPORT_SYMBOL(arm64_pbha_perf_only_values);
 
 /*
  * Permit PER_LINUX32 and execve() of 32-bit binaries even if not all CPUs
-- 
2.30.2