[PATCH v4 02/10] ARM: KVM: Hypervisor identity mapping

[Christoffer Dall <cdall@xxxxxxxxxxxxxxx>]

Adds support in the identity mapping feature that allows KVM to setup
identity mapping for the Hyp mode with the AP[1] bit set as required by
the specification and also supports freeing created sub pmd's after
finished use.

These two functions:
 - hyp_identity_mapping_add(pgd, addr, end);
 - hyp_identity_mapping_del(pgd, addr, end);
are essentially calls the same function as the non-hyp versions but
with a different argument value. KVM calls these functions to setup
and teardown the identity mapping used to initialize the hypervisor.

Note, the hyp-version of the _del function actually frees the pmd's
pointed to by the pgd as opposed to the non-hyp version which just
clears them.

Signed-off-by: Christoffer Dall <c.dall@xxxxxxxxxxxxxxxxxxxxxx>
---
 arch/arm/include/asm/pgtable-3level-hwdef.h |    1 +
 arch/arm/include/asm/pgtable.h              |    6 +++
 arch/arm/mm/idmap.c                         |   47 ++++++++++++++++++++++++++-
 3 files changed, 53 insertions(+), 1 deletions(-)

diff --git a/arch/arm/include/asm/pgtable-3level-hwdef.h b/arch/arm/include/asm/pgtable-3level-hwdef.h
index 7c238a3..8ed298f 100644
--- a/arch/arm/include/asm/pgtable-3level-hwdef.h
+++ b/arch/arm/include/asm/pgtable-3level-hwdef.h
@@ -49,6 +49,7 @@
 #endif
 #define PMD_SECT_AP_WRITE	(_AT(pmdval_t, 0))
 #define PMD_SECT_AP_READ	(_AT(pmdval_t, 0))
+#define PMD_SECT_AP1		(_AT(pmdval_t, 1) << 6)
 #define PMD_SECT_TEX(x)		(_AT(pmdval_t, 0))
 
 /*
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 9645e52..da74cd1 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -409,6 +409,12 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 void identity_mapping_add(pgd_t *, unsigned long, unsigned long);
 void identity_mapping_del(pgd_t *, unsigned long, unsigned long);
 
+#ifdef CONFIG_KVM_ARM_HOST
+void hyp_identity_mapping_add(pgd_t *, unsigned long, unsigned long);
+void hyp_identity_mapping_del(pgd_t *pgd, unsigned long addr,
+			      unsigned long end);
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* CONFIG_MMU */
diff --git a/arch/arm/mm/idmap.c b/arch/arm/mm/idmap.c
index 24e0655..83dc20d 100644
--- a/arch/arm/mm/idmap.c
+++ b/arch/arm/mm/idmap.c
@@ -56,11 +56,16 @@ static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
 	} while (pud++, addr = next, addr != end);
 }
 
-void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)
+static void __identity_mapping_add(pgd_t *pgd, unsigned long addr,
+				   unsigned long end, bool hyp_mapping)
 {
 	unsigned long prot, next;
 
 	prot = PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AF;
+
+	if (hyp_mapping)
+		prot |= PMD_SECT_AP1;
+
 	if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale())
 		prot |= PMD_BIT4;
 
@@ -71,6 +76,12 @@ void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)
 	} while (pgd++, addr = next, addr != end);
 }
 
+void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)
+{
+	__identity_mapping_add(pgd, addr, end, false);
+}
+
+
 #ifdef CONFIG_SMP
 static void idmap_del_pmd(pud_t *pud, unsigned long addr, unsigned long end)
 {
@@ -105,6 +116,40 @@ void identity_mapping_del(pgd_t *pgd, unsigned long addr, unsigned long end)
 }
 #endif
 
+#ifdef CONFIG_KVM_ARM_HOST
+void hyp_identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)
+{
+	__identity_mapping_add(pgd, addr, end, true);
+}
+
+static void hyp_idmap_del_pmd(pgd_t *pgd, unsigned long addr)
+{
+	pmd_t *pmd;
+
+	pmd = pmd_offset(pgd, addr);
+	pmd_free(NULL, pmd);
+}
+
+/*
+ * This version actually frees the underlying pmds for all pgds in range and
+ * clear the pgds themselves afterwards.
+ */
+void hyp_identity_mapping_del(pgd_t *pgd, unsigned long addr, unsigned long end)
+{
+	unsigned long next;
+	pgd_t *next_pgd;
+
+	do {
+		next = pgd_addr_end(addr, end);
+		next_pgd = pgd + pgd_index(addr);
+		if (!pgd_none_or_clear_bad(next_pgd)) {
+			hyp_idmap_del_pmd(next_pgd, addr);
+			pgd_clear(next_pgd);
+		}
+	} while (addr = next, addr < end);
+}
+#endif
+
 /*
  * In order to soft-boot, we need to insert a 1:1 mapping in place of
  * the user-mode pages.  This will then ensure that we have predictable

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