[PATCH v3 05/21] KVM: arm64: Add support for creating kernel-agnostic stage-2 page tables

Will Deacon
2020-08-25T09:43:04Z

Introduce alloc() and free() functions to the generic page-table code
for guest stage-2 page-tables and plumb these into the existing KVM
page-table allocator. Subsequent patches will convert other operations
within the KVM allocator over to the generic code.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/include/asm/kvm_pgtable.h | 18 +++++++++
arch/arm64/kvm/hyp/pgtable.c | 51 ++++++++++++++++++++++++++
arch/arm64/kvm/mmu.c | 55 +++++++++++++++-------------
4 files changed, 99 insertions(+), 26 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e52c927aade5..0b7c702b2151 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -81,6 +81,7 @@ struct kvm_s2_mmu {
*/
pgd_t *pgd;
phys_addr_t pgd_phys;
+ struct kvm_pgtable *pgt;

/* The last vcpu id that ran on each physical CPU */
int __percpu *last_vcpu_ran;
diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 2af84ab78cb8..3389f978d573 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -116,6 +116,24 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt);
int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
enum kvm_pgtable_prot prot);

+/**
+ * kvm_pgtable_stage2_init() - Initialise a guest stage-2 page-table.
+ * @pgt: Uninitialised page-table structure to initialise.
+ * @kvm: KVM structure representing the guest virtual machine.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm *kvm);
+
+/**
+ * kvm_pgtable_stage2_destroy() - Destroy an unused guest stage-2 page-table.
+ * @pgt: Page-table structure initialised by kvm_pgtable_stage2_init().
+ *
+ * The page-table is assumed to be unreachable by any hardware walkers prior
+ * to freeing and therefore no TLB invalidation is performed.
+ */
+void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
+
/**
* kvm_pgtable_walk() - Walk a page-table.
* @pgt: Page-table structure initialised by kvm_pgtable_*_init().
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index d75166823ad9..b8550ccaef4d 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -419,3 +419,54 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
free_page((unsigned long)pgt->pgd);
pgt->pgd = NULL;
}
+
+int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm *kvm)
+{
+ size_t pgd_sz;
+ u64 vtcr = kvm->arch.vtcr;
+ u32 ia_bits = VTCR_EL2_IPA(vtcr);
+ u32 sl0 = FIELD_GET(VTCR_EL2_SL0_MASK, vtcr);
+ u32 start_level = VTCR_EL2_TGRAN_SL0_BASE - sl0;
+
+ pgd_sz = kvm_pgd_pages(ia_bits, start_level) * PAGE_SIZE;
+ pgt->pgd = alloc_pages_exact(pgd_sz, GFP_KERNEL | __GFP_ZERO);
+ if (!pgt->pgd)
+ return -ENOMEM;
+
+ pgt->ia_bits = ia_bits;
+ pgt->start_level = start_level;
+ pgt->mmu = &kvm->arch.mmu;
+ return 0;
+}
+
+static int stage2_free_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+ enum kvm_pgtable_walk_flags flag,
+ void * const arg)
+{
+ kvm_pte_t pte = *ptep;
+
+ if (!kvm_pte_valid(pte))
+ return 0;
+
+ put_page(virt_to_page(ptep));
+
+ if (kvm_pte_table(pte, level))
+ free_page((unsigned long)kvm_pte_follow(pte));
+
+ return 0;
+}
+
+void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
+{
+ size_t pgd_sz;
+ struct kvm_pgtable_walker walker = {
+ .cb = stage2_free_walker,
+ .flags = KVM_PGTABLE_WALK_LEAF |
+ KVM_PGTABLE_WALK_TABLE_POST,
+ };
+
+ WARN_ON(kvm_pgtable_walk(pgt, 0, BIT(pgt->ia_bits), &walker));
+ pgd_sz = kvm_pgd_pages(pgt->ia_bits, pgt->start_level) * PAGE_SIZE;
+ free_pages_exact(pgt->pgd, pgd_sz);
+ pgt->pgd = NULL;
+}
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index fabd72b0c8a4..4607e9ca60a2 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -668,47 +668,49 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
* @kvm: The pointer to the KVM structure
* @mmu: The pointer to the s2 MMU structure
*
- * Allocates only the stage-2 HW PGD level table(s) of size defined by
- * stage2_pgd_size(mmu->kvm).
- *
+ * Allocates only the stage-2 HW PGD level table(s).
* Note we don't need locking here as this is only called when the VM is
* created, which can only be done once.
*/
int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu)
{
- phys_addr_t pgd_phys;
- pgd_t *pgd;
- int cpu;
+ int cpu, err;
+ struct kvm_pgtable *pgt;

- if (mmu->pgd != NULL) {
+ if (mmu->pgt != NULL) {
kvm_err("kvm_arch already initialized?\n");
return -EINVAL;
}

- /* Allocate the HW PGD, making sure that each page gets its own refcount */
- pgd = alloc_pages_exact(stage2_pgd_size(kvm), GFP_KERNEL | __GFP_ZERO);
- if (!pgd)
+ pgt = kzalloc(sizeof(*pgt), GFP_KERNEL);
+ if (!pgt)
return -ENOMEM;

- pgd_phys = virt_to_phys(pgd);
- if (WARN_ON(pgd_phys & ~kvm_vttbr_baddr_mask(kvm)))
- return -EINVAL;
+ err = kvm_pgtable_stage2_init(pgt, kvm);
+ if (err)
+ goto out_free_pgtable;

mmu->last_vcpu_ran = alloc_percpu(typeof(*mmu->last_vcpu_ran));
if (!mmu->last_vcpu_ran) {
- free_pages_exact(pgd, stage2_pgd_size(kvm));
- return -ENOMEM;
+ err = -ENOMEM;
+ goto out_destroy_pgtable;
}

for_each_possible_cpu(cpu)
*per_cpu_ptr(mmu->last_vcpu_ran, cpu) = -1;

mmu->kvm = kvm;
- mmu->pgd = pgd;
- mmu->pgd_phys = pgd_phys;
+ mmu->pgt = pgt;
+ mmu->pgd_phys = __pa(pgt->pgd);
+ mmu->pgd = (void *)pgt->pgd;
mmu->vmid.vmid_gen = 0;
-
return 0;
+
+out_destroy_pgtable:
+ kvm_pgtable_stage2_destroy(pgt);
+out_free_pgtable:
+ kfree(pgt);
+ return err;
}

static void stage2_unmap_memslot(struct kvm *kvm,
@@ -781,20 +783,21 @@ void stage2_unmap_vm(struct kvm *kvm)
void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
{
struct kvm *kvm = mmu->kvm;
- void *pgd = NULL;
+ struct kvm_pgtable *pgt = NULL;

spin_lock(&kvm->mmu_lock);
- if (mmu->pgd) {
- unmap_stage2_range(mmu, 0, kvm_phys_size(kvm));
- pgd = READ_ONCE(mmu->pgd);
+ pgt = mmu->pgt;
+ if (pgt) {
mmu->pgd = NULL;
+ mmu->pgd_phys = 0;
+ mmu->pgt = NULL;
+ free_percpu(mmu->last_vcpu_ran);
}
spin_unlock(&kvm->mmu_lock);

- /* Free the HW pgd, one page at a time */
- if (pgd) {
- free_pages_exact(pgd, stage2_pgd_size(kvm));
- free_percpu(mmu->last_vcpu_ran);
+ if (pgt) {
+ kvm_pgtable_stage2_destroy(pgt);
+ kfree(pgt);
}
}

--
2.28.0.297.g1956fa8f8d-goog