[PATCH v2 2/9] KVM: arm64: Introduce pkvm_alloc_private_va_range()

Kalesh Singh
2022-02-22T16:55:01Z

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

These will be used to implement stack guard pages for pKVM nVHE hypervisor
(in a subsequent patch in the series).

Credits to Quentin Perret <qperret@google.com> for the idea of moving
private VA allocation out of __pkvm_create_private_mapping()

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

Changes in v2:
- Allow specifying an alignment for the private VA allocations, per Marc

arch/arm64/kvm/hyp/include/nvhe/mm.h | 3 +-
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 5 +--
arch/arm64/kvm/hyp/nvhe/mm.c | 49 +++++++++++++++++++---------
arch/arm64/kvm/mmu.c | 2 +-
4 files changed, 39 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/mm.h b/arch/arm64/kvm/hyp/include/nvhe/mm.h
index 2d08510c6cc1..05d06ad00347 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mm.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mm.h
@@ -20,7 +20,8 @@ int pkvm_cpu_set_vector(enum arm64_hyp_spectre_vector slot);
int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot);
int pkvm_create_mappings_locked(void *from, void *to, enum kvm_pgtable_prot prot);
unsigned long __pkvm_create_private_mapping(phys_addr_t phys, size_t size,
- enum kvm_pgtable_prot prot);
+ size_t align, enum kvm_pgtable_prot prot);
+unsigned long pkvm_alloc_private_va_range(size_t size, size_t align);

static inline void hyp_vmemmap_range(phys_addr_t phys, unsigned long size,
unsigned long *start, unsigned long *end)
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 5e2197db0d32..96b2312a0f1d 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -158,9 +158,10 @@ static void handle___pkvm_create_private_mapping(struct kvm_cpu_context *host_ct
{
DECLARE_REG(phys_addr_t, phys, host_ctxt, 1);
DECLARE_REG(size_t, size, host_ctxt, 2);
- DECLARE_REG(enum kvm_pgtable_prot, prot, host_ctxt, 3);
+ DECLARE_REG(size_t, align, host_ctxt, 3);
+ DECLARE_REG(enum kvm_pgtable_prot, prot, host_ctxt, 4);

- cpu_reg(host_ctxt, 1) = __pkvm_create_private_mapping(phys, size, prot);
+ cpu_reg(host_ctxt, 1) = __pkvm_create_private_mapping(phys, size, align, prot);
}

static void handle___pkvm_prot_finalize(struct kvm_cpu_context *host_ctxt)
diff --git a/arch/arm64/kvm/hyp/nvhe/mm.c b/arch/arm64/kvm/hyp/nvhe/mm.c
index 526a7d6fa86f..298fbbe4651d 100644
--- a/arch/arm64/kvm/hyp/nvhe/mm.c
+++ b/arch/arm64/kvm/hyp/nvhe/mm.c
@@ -37,26 +37,46 @@ static int __pkvm_create_mappings(unsigned long start, unsigned long size,
return err;
}

-unsigned long __pkvm_create_private_mapping(phys_addr_t phys, size_t size,
- enum kvm_pgtable_prot prot)
+/*
+ * Allocates a private VA range above __io_map_base.
+ *
+ * @size: The size of the VA range to reserve.
+ * @align: The required alignment for the allocation.
+ */
+unsigned long pkvm_alloc_private_va_range(size_t size, size_t align)
{
- unsigned long addr;
- int err;
+ unsigned long base, addr;

hyp_spin_lock(&pkvm_pgd_lock);

- size = PAGE_ALIGN(size + offset_in_page(phys));
- addr = __io_map_base;
- __io_map_base += size;
+ addr = ALIGN(__io_map_base, align);
+
+ /* The allocated size is always a multiple of PAGE_SIZE */
+ base = addr + PAGE_ALIGN(size);

/* Are we overflowing on the vmemmap ? */
- if (__io_map_base > __hyp_vmemmap) {
- __io_map_base -= size;
+ if (base > __hyp_vmemmap)
addr = (unsigned long)ERR_PTR(-ENOMEM);
+ else
+ __io_map_base = base;
+
+ hyp_spin_unlock(&pkvm_pgd_lock);
+
+ return addr;
+}
+
+unsigned long __pkvm_create_private_mapping(phys_addr_t phys, size_t size,
+ size_t align, enum kvm_pgtable_prot prot)
+{
+ unsigned long addr;
+ int err;
+
+ size += offset_in_page(phys);
+ addr = pkvm_alloc_private_va_range(size, align);
+ if (IS_ERR((void *)addr))
goto out;
- }

- err = kvm_pgtable_hyp_map(&pkvm_pgtable, addr, size, phys, prot);
+ err = __pkvm_create_mappings(addr, size, phys, prot);
if (err) {
addr = (unsigned long)ERR_PTR(err);
goto out;
@@ -64,8 +84,6 @@ unsigned long __pkvm_create_private_mapping(phys_addr_t phys, size_t size,

addr = addr + offset_in_page(phys);
out:
- hyp_spin_unlock(&pkvm_pgd_lock);
-
return addr;
}

@@ -152,9 +170,8 @@ int hyp_map_vectors(void)
return 0;

phys = __hyp_pa(__bp_harden_hyp_vecs);
- bp_base = (void *)__pkvm_create_private_mapping(phys,
- __BP_HARDEN_HYP_VECS_SZ,
- PAGE_HYP_EXEC);
+ bp_base = (void *)__pkvm_create_private_mapping(phys, __BP_HARDEN_HYP_VECS_SZ,
+ PAGE_SIZE, PAGE_HYP_EXEC);
if (IS_ERR_OR_NULL(bp_base))
return PTR_ERR(bp_base);

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index e5abcce44ad0..18a711d6a52f 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -505,7 +505,7 @@ int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,

if (!kvm_host_owns_hyp_mappings()) {
addr = kvm_call_hyp_nvhe(__pkvm_create_private_mapping,
- phys_addr, size, prot);
+ phys_addr, size, align, prot);
if (IS_ERR_OR_NULL((void *)addr))
return PTR_ERR((void *)addr);
*haddr = addr;
--
2.35.1.473.g83b2b277ed-goog