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Subject[RFC V2 08/10] arm64/mm: Add FEAT_LPA2 specific PTE_SHARED and PMD_SECT_S
Date
PTE[9:8] which holds the sharability attribute bits SH[1:0] could collide
with PA[51:50] when CONFIG_ARM64_PA_BITS_52 is enabled but then FEAT_LPA2
is not detected during boot. Dropping PTE_SHARED and PMD_SECT_S attributes
completely in this scenario will create non-shared page table entries which
would cause regression.

Instead just define PTE_SHARED and PMD_SECT_S after accounting for runtime
'arm64_lpa2_enable', thus maintaining required sharability attributes for
both kernel and user space page table entries. This updates ptdump handling
for page table entry shared attributes accommodating FEAT_LPA2 scenarios.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
arch/arm64/include/asm/pgtable-hwdef.h | 12 ++++++++++--
arch/arm64/kernel/head.S | 15 +++++++++++++++
arch/arm64/mm/ptdump.c | 26 ++++++++++++++++++++++++--
4 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 3512184..db682b5 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -103,8 +103,8 @@
/*
* Initial memory map attributes.
*/
-#define SWAPPER_PTE_FLAGS (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
-#define SWAPPER_PMD_FLAGS (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
+#define SWAPPER_PTE_FLAGS (PTE_TYPE_PAGE | PTE_AF)
+#define SWAPPER_PMD_FLAGS (PMD_TYPE_SECT | PMD_SECT_AF)

#if ARM64_KERNEL_USES_PMD_MAPS
#define SWAPPER_MM_MMUFLAGS (PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index c815a85..8a3b75e 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -116,13 +116,21 @@
#define PMD_TYPE_SECT (_AT(pmdval_t, 1) << 0)
#define PMD_TABLE_BIT (_AT(pmdval_t, 1) << 1)

+#ifdef CONFIG_ARM64_PA_BITS_52_LPA2
+#define PTE_SHARED (arm64_lpa2_enabled ? 0 : PTE_SHARED_STATIC)
+#define PMD_SECT_S (arm64_lpa2_enabled ? 0 : PMD_SECT_S_STATIC)
+#else /* !CONFIG_ARM64_PA_BITS_52_LPA2 */
+#define PTE_SHARED PTE_SHARED_STATIC
+#define PMD_SECT_S PMD_SECT_S_STATIC
+#endif /* CONFIG_ARM64_PA_BITS_52_LPA2 */
+
/*
* Section
*/
#define PMD_SECT_VALID (_AT(pmdval_t, 1) << 0)
#define PMD_SECT_USER (_AT(pmdval_t, 1) << 6) /* AP[1] */
#define PMD_SECT_RDONLY (_AT(pmdval_t, 1) << 7) /* AP[2] */
-#define PMD_SECT_S (_AT(pmdval_t, 3) << 8)
+#define PMD_SECT_S_STATIC (_AT(pmdval_t, 3) << 8)
#define PMD_SECT_AF (_AT(pmdval_t, 1) << 10)
#define PMD_SECT_NG (_AT(pmdval_t, 1) << 11)
#define PMD_SECT_CONT (_AT(pmdval_t, 1) << 52)
@@ -146,7 +154,7 @@
#define PTE_TABLE_BIT (_AT(pteval_t, 1) << 1)
#define PTE_USER (_AT(pteval_t, 1) << 6) /* AP[1] */
#define PTE_RDONLY (_AT(pteval_t, 1) << 7) /* AP[2] */
-#define PTE_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */
+#define PTE_SHARED_STATIC (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */
#define PTE_AF (_AT(pteval_t, 1) << 10) /* Access Flag */
#define PTE_NG (_AT(pteval_t, 1) << 11) /* nG */
#define PTE_GP (_AT(pteval_t, 1) << 50) /* BTI guarded */
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index efc6e41..f8b2399 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -301,6 +301,21 @@ SYM_FUNC_START_LOCAL(__create_page_tables)

mov x7, SWAPPER_MM_MMUFLAGS

+#ifdef CONFIG_ARM64_PA_BITS_52_LPA2
+ ldr_l x2, arm64_lpa2_enabled
+ cmp x2, #1
+ b.eq 1f
+#endif /* CONFIG_ARM64_PA_BITS_52_LPA2 */
+
+ /*
+ * FEAT_LPA2 has not been detected during boot.
+ * Hence SWAPPER_MM_MMUFLAGS needs to have the
+ * regular sharability attributes in PTE[9:8].
+ * Same is also applicable when FEAT_LPA2 has
+ * not been requested in the first place.
+ */
+ orr x7, x7, PTE_SHARED_STATIC
+1:
/*
* Create the identity mapping.
*/
diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 1c40353..be171cf 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -115,8 +115,8 @@ static const struct prot_bits pte_bits[] = {
.set = "NX",
.clear = "x ",
}, {
- .mask = PTE_SHARED,
- .val = PTE_SHARED,
+ .mask = PTE_SHARED_STATIC,
+ .val = PTE_SHARED_STATIC,
.set = "SHD",
.clear = " ",
}, {
@@ -211,6 +211,28 @@ static void dump_prot(struct pg_state *st, const struct prot_bits *bits,
for (i = 0; i < num; i++, bits++) {
const char *s;

+ if (IS_ENABLED(CONFIG_ARM64_PA_BITS_52_LPA2) &&
+ (bits->mask == PTE_SHARED_STATIC)) {
+ /*
+ * If FEAT_LPA2 has been detected and enabled
+ * sharing attributes for page table entries
+ * are inherited from TCR_EL1.SH1 as init_mm
+ * based mappings are enabled from TTBR1_EL1.
+ */
+ if (arm64_lpa2_enabled) {
+ if ((read_sysreg(tcr_el1) & TCR_SH1_INNER) == TCR_SH1_INNER)
+ pt_dump_seq_printf(st->seq, " SHD ");
+ else
+ pt_dump_seq_printf(st->seq, " ");
+ continue;
+ }
+ /*
+ * In case FEAT_LPA2 has not been detected and
+ * enabled sharing attributes should be found
+ * in the regular PTE positions. It just falls
+ * through regular PTE attribute handling.
+ */
+ }
if ((st->current_prot & bits->mask) == bits->val)
s = bits->set;
else
--
2.7.4
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