[PATCH v4 1/8] KVM: arm64: Introduce hyp_alloc_private_va_range()

[Kalesh Singh <kaleshsingh@google.com>]

hyp_alloc_private_va_range() can be used to reserve private VA ranges
in the nVHE hypervisor. Also update  __create_hyp_private_mapping()
to allow specifying an alignment for the private VA mapping.

These will be used to implement stack guard pages for KVM nVHE hypervisor
(nVHE Hyp mode / not pKVM), in a subsequent patch in the series.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---

Changes in v4:
  - Handle null ptr in hyp_alloc_private_va_range() and replace
    IS_ERR_OR_NULL checks in callers with IS_ERR checks, per Fuad
  - Fix kernel-doc comments format, per Fuad

Changes in v3:
  - Handle null ptr in IS_ERR_OR_NULL checks, per Mark

 arch/arm64/include/asm/kvm_mmu.h |  4 ++
 arch/arm64/kvm/mmu.c             | 65 ++++++++++++++++++++------------
 2 files changed, 45 insertions(+), 24 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 81839e9a8a24..0b0c71302b92 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -153,6 +153,10 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v)
 int kvm_share_hyp(void *from, void *to);
 void kvm_unshare_hyp(void *from, void *to);
 int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot);
+unsigned long hyp_alloc_private_va_range(size_t size, size_t align);
+int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
+				size_t align, unsigned long *haddr,
+				enum kvm_pgtable_prot prot);
 int create_hyp_io_mappings(phys_addr_t phys_addr, size_t size,
 			   void __iomem **kaddr,
 			   void __iomem **haddr);
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index bc2aba953299..a4868a6fa1c3 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -457,22 +457,17 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
 	return 0;
 }
 
-static int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
-					unsigned long *haddr,
-					enum kvm_pgtable_prot prot)
+
+/**
+ * hyp_alloc_private_va_range - Allocates a private VA range.
+ * @size:	The size of the VA range to reserve.
+ * @align:	The required alignment for the allocation.
+ *
+ * The private VA range is allocated below io_map_base.
+ */
+unsigned long hyp_alloc_private_va_range(size_t size, size_t align)
 {
 	unsigned long base;
-	int ret = 0;
-
-	if (!kvm_host_owns_hyp_mappings()) {
-		base = kvm_call_hyp_nvhe(__pkvm_create_private_mapping,
-					 phys_addr, size, prot);
-		if (IS_ERR_OR_NULL((void *)base))
-			return PTR_ERR((void *)base);
-		*haddr = base;
-
-		return 0;
-	}
 
 	mutex_lock(&kvm_hyp_pgd_mutex);
 
@@ -484,29 +479,51 @@ static int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
 	 *
 	 * The allocated size is always a multiple of PAGE_SIZE.
 	 */
-	size = PAGE_ALIGN(size + offset_in_page(phys_addr));
-	base = io_map_base - size;
+	base = io_map_base - PAGE_ALIGN(size);
+	base = ALIGN_DOWN(base, align);
 
 	/*
 	 * Verify that BIT(VA_BITS - 1) hasn't been flipped by
 	 * allocating the new area, as it would indicate we've
 	 * overflowed the idmap/IO address range.
 	 */
-	if ((base ^ io_map_base) & BIT(VA_BITS - 1))
-		ret = -ENOMEM;
+	if (!base || (base ^ io_map_base) & BIT(VA_BITS - 1))
+		base = (unsigned long)ERR_PTR(-ENOMEM);
 	else
 		io_map_base = base;
 
 	mutex_unlock(&kvm_hyp_pgd_mutex);
 
-	if (ret)
-		goto out;
+	return base;
+}
+
+int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
+				size_t align, unsigned long *haddr,
+				enum kvm_pgtable_prot prot)
+{
+	unsigned long addr;
+	int ret = 0;
+
+	if (!kvm_host_owns_hyp_mappings()) {
+		addr = kvm_call_hyp_nvhe(__pkvm_create_private_mapping,
+					 phys_addr, size, prot);
+		if (IS_ERR((void *)addr))
+			return PTR_ERR((void *)addr);
+		*haddr = addr;
+
+		return 0;
+	}
+
+	size += offset_in_page(phys_addr);
+	addr = hyp_alloc_private_va_range(size, align);
+	if (IS_ERR((void *)addr))
+		return PTR_ERR((void *)addr);
 
-	ret = __create_hyp_mappings(base, size, phys_addr, prot);
+	ret = __create_hyp_mappings(addr, size, phys_addr, prot);
 	if (ret)
 		goto out;
 
-	*haddr = base + offset_in_page(phys_addr);
+	*haddr = addr + offset_in_page(phys_addr);
 out:
 	return ret;
 }
@@ -537,7 +554,7 @@ int create_hyp_io_mappings(phys_addr_t phys_addr, size_t size,
 		return 0;
 	}
 
-	ret = __create_hyp_private_mapping(phys_addr, size,
+	ret = __create_hyp_private_mapping(phys_addr, size, PAGE_SIZE,
 					   &addr, PAGE_HYP_DEVICE);
 	if (ret) {
 		iounmap(*kaddr);
@@ -564,7 +581,7 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
 
 	BUG_ON(is_kernel_in_hyp_mode());
 
-	ret = __create_hyp_private_mapping(phys_addr, size,
+	ret = __create_hyp_private_mapping(phys_addr, size, PAGE_SIZE,
 					   &addr, PAGE_HYP_EXEC);
 	if (ret) {
 		*haddr = NULL;
-- 
2.35.1.574.g5d30c73bfb-goog

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