[PATCH v4 06/15] arm64: Make the PHYS_MASK_SHIFT dynamic

Steven Price
2024-07-01T09:55:38Z

Make the PHYS_MASK_SHIFT dynamic for Realms. This is only is required
for masking the PFN from a pte entry. For a realm phys_mask_shift is
reduced if the RMM reports a smaller configured size for the guest.

The realm configuration splits the address space into two with the top
half being memory shared with the host, and the bottom half being
protected memory. We treat the bit which controls this split as an
attribute bit and hence exclude it (and any higher bits) from the mask.

Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>

---
v3: Drop the MAX_PHYS_MASK{,_SHIFT} definitions as they are no longer
needed.
---
arch/arm64/include/asm/pgtable-hwdef.h | 6 ------
arch/arm64/include/asm/pgtable.h | 5 +++++
arch/arm64/kernel/rsi.c | 5 +++++
3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index 9943ff0af4c9..2e3af0693bd8 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -203,12 +203,6 @@
*/
#define PTE_S2_MEMATTR(t) (_AT(pteval_t, (t)) << 2)

-/*
- * Highest possible physical address supported.
- */
-#define PHYS_MASK_SHIFT (CONFIG_ARM64_PA_BITS)
-#define PHYS_MASK ((UL(1) << PHYS_MASK_SHIFT) - 1)
-
#define TTBR_CNP_BIT (UL(1) << 0)

/*
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index f8efbc128446..11d614d83317 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -39,6 +39,11 @@
#include <linux/sched.h>
#include <linux/page_table_check.h>

+extern unsigned int phys_mask_shift;
+
+#define PHYS_MASK_SHIFT (phys_mask_shift)
+#define PHYS_MASK ((1UL << PHYS_MASK_SHIFT) - 1)
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE

diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
index 231c1a3ecdeb..7ac5fc4a27d0 100644
--- a/arch/arm64/kernel/rsi.c
+++ b/arch/arm64/kernel/rsi.c
@@ -13,6 +13,8 @@ struct realm_config config;
unsigned long prot_ns_shared;
EXPORT_SYMBOL(prot_ns_shared);

+unsigned int phys_mask_shift = CONFIG_ARM64_PA_BITS;
+
DEFINE_STATIC_KEY_FALSE_RO(rsi_present);
EXPORT_SYMBOL(rsi_present);

@@ -80,6 +82,9 @@ void __init arm64_rsi_init(void)
return;
prot_ns_shared = BIT(config.ipa_bits - 1);

+ if (config.ipa_bits - 1 < phys_mask_shift)
+ phys_mask_shift = config.ipa_bits - 1;
+
static_branch_enable(&rsi_present);
}

--
2.34.1