[PATCH v2 1/9] KVM: arm64: Introduce hyp_alloc_private_va_range()

Kalesh Singh
2022-02-22T16:53:54Z

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>
---
arch/arm64/include/asm/kvm_mmu.h | 4 +++
arch/arm64/kvm/mmu.c | 61 +++++++++++++++++++++-----------
2 files changed, 44 insertions(+), 21 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..e5abcce44ad0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -457,22 +457,16 @@ 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)
+
+/*
+ * Allocates a private VA range below io_map_base.
+ *
+ * @size: The size of the VA range to reserve.
+ * @align: The required alignment for the allocation.
+ */
+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);

@@ -484,8 +478,8 @@ 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
@@ -493,20 +487,45 @@ static int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
* overflowed the idmap/IO address range.
*/
if ((base ^ io_map_base) & BIT(VA_BITS - 1))
- ret = -ENOMEM;
+ base = (unsigned long)ERR_PTR(-ENOMEM);
else
io_map_base = base;

mutex_unlock(&kvm_hyp_pgd_mutex);

+ 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_OR_NULL((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_OR_NULL((void *)addr))
+ return PTR_ERR((void *)addr);
+
if (ret)
goto out;

- 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 +556,7 @@ 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 +583,7 @@ 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;
--
2.35.1.473.g83b2b277ed-goog