[PATCH v3 19/25] KVM: arm64: Instantiate guest stage-2 page-tables at EL2

Will Deacon
2022-09-14T08:36:40Z

Extend the initialisation of guest data structures within the pKVM
hypervisor at EL2 so that we instantiate a memory pool and a full
'struct kvm_s2_mmu' structure for each VM, with a stage-2 page-table
entirely independent from the one managed by the host at EL1.

The 'struct kvm_pgtable_mm_ops' used by the page-table code is populated
with a set of callbacks that can manage guest pages in the hypervisor
without any direct intervention from the host, allocating page-table
pages from the provided pool and returning these to the host on VM
teardown. To keep things simple, the stage-2 MMU for the guest is
configured identically to the host stage-2 in the VTCR register and so
the IPA size of the guest must match the PA size of the host.

For now, the new page-table is unused as there is no way for the host
to map anything into it. Yet.

Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kvm/hyp/include/nvhe/pkvm.h | 6 ++
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 125 ++++++++++++++++++++++++-
arch/arm64/kvm/mmu.c | 4 +-
3 files changed, 132 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
index d176399dbfb5..5d456438445c 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
@@ -9,6 +9,9 @@

#include <asm/kvm_pkvm.h>

+#include <nvhe/gfp.h>
+#include <nvhe/spinlock.h>
+
/*
* Holds the relevant data for maintaining the vcpu state completely at hyp.
*/
@@ -36,6 +39,9 @@ struct pkvm_hyp_vm {

/* The guest's stage-2 page-table managed by the hypervisor. */
struct kvm_pgtable pgt;
+ struct kvm_pgtable_mm_ops mm_ops;
+ struct hyp_pool pool;
+ hyp_spinlock_t lock;

/*
* The number of vcpus initialized and ready to run.
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 1c38451050e5..27b16a6b85bb 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -25,6 +25,21 @@ struct host_mmu host_mmu;

static struct hyp_pool host_s2_pool;

+static DEFINE_PER_CPU(struct pkvm_hyp_vm *, __current_vm);
+#define current_vm (*this_cpu_ptr(&__current_vm))
+
+static void guest_lock_component(struct pkvm_hyp_vm *vm)
+{
+ hyp_spin_lock(&vm->lock);
+ current_vm = vm;
+}
+
+static void guest_unlock_component(struct pkvm_hyp_vm *vm)
+{
+ current_vm = NULL;
+ hyp_spin_unlock(&vm->lock);
+}
+
static void host_lock_component(void)
{
hyp_spin_lock(&host_mmu.lock);
@@ -140,18 +155,124 @@ int kvm_host_prepare_stage2(void *pgt_pool_base)
return 0;
}

+static bool guest_stage2_force_pte_cb(u64 addr, u64 end,
+ enum kvm_pgtable_prot prot)
+{
+ return true;
+}
+
+static void *guest_s2_zalloc_pages_exact(size_t size)
+{
+ void *addr = hyp_alloc_pages(&current_vm->pool, get_order(size));
+
+ WARN_ON(size != (PAGE_SIZE << get_order(size)));
+ hyp_split_page(hyp_virt_to_page(addr));
+
+ return addr;
+}
+
+static void guest_s2_free_pages_exact(void *addr, unsigned long size)
+{
+ u8 order = get_order(size);
+ unsigned int i;
+
+ for (i = 0; i < (1 << order); i++)
+ hyp_put_page(&current_vm->pool, addr + (i * PAGE_SIZE));
+}
+
+static void *guest_s2_zalloc_page(void *mc)
+{
+ struct hyp_page *p;
+ void *addr;
+
+ addr = hyp_alloc_pages(&current_vm->pool, 0);
+ if (addr)
+ return addr;
+
+ addr = pop_hyp_memcache(mc, hyp_phys_to_virt);
+ if (!addr)
+ return addr;
+
+ memset(addr, 0, PAGE_SIZE);
+ p = hyp_virt_to_page(addr);
+ memset(p, 0, sizeof(*p));
+ p->refcount = 1;
+
+ return addr;
+}
+
+static void guest_s2_get_page(void *addr)
+{
+ hyp_get_page(&current_vm->pool, addr);
+}
+
+static void guest_s2_put_page(void *addr)
+{
+ hyp_put_page(&current_vm->pool, addr);
+}
+
+static void clean_dcache_guest_page(void *va, size_t size)
+{
+ __clean_dcache_guest_page(hyp_fixmap_map(__hyp_pa(va)), size);
+ hyp_fixmap_unmap();
+}
+
+static void invalidate_icache_guest_page(void *va, size_t size)
+{
+ __invalidate_icache_guest_page(hyp_fixmap_map(__hyp_pa(va)), size);
+ hyp_fixmap_unmap();
+}
+
int kvm_guest_prepare_stage2(struct pkvm_hyp_vm *vm, void *pgd)
{
- vm->pgt.pgd = pgd;
+ struct kvm_s2_mmu *mmu = &vm->kvm.arch.mmu;
+ unsigned long nr_pages;
+ int ret;
+
+ nr_pages = kvm_pgtable_stage2_pgd_size(vm->kvm.arch.vtcr) >> PAGE_SHIFT;
+ ret = hyp_pool_init(&vm->pool, hyp_virt_to_pfn(pgd), nr_pages, 0);
+ if (ret)
+ return ret;
+
+ hyp_spin_lock_init(&vm->lock);
+ vm->mm_ops = (struct kvm_pgtable_mm_ops) {
+ .zalloc_pages_exact = guest_s2_zalloc_pages_exact,
+ .free_pages_exact = guest_s2_free_pages_exact,
+ .zalloc_page = guest_s2_zalloc_page,
+ .phys_to_virt = hyp_phys_to_virt,
+ .virt_to_phys = hyp_virt_to_phys,
+ .page_count = hyp_page_count,
+ .get_page = guest_s2_get_page,
+ .put_page = guest_s2_put_page,
+ .dcache_clean_inval_poc = clean_dcache_guest_page,
+ .icache_inval_pou = invalidate_icache_guest_page,
+ };
+
+ guest_lock_component(vm);
+ ret = __kvm_pgtable_stage2_init(mmu->pgt, mmu, &vm->mm_ops, 0,
+ guest_stage2_force_pte_cb);
+ guest_unlock_component(vm);
+ if (ret)
+ return ret;
+
+ vm->kvm.arch.mmu.pgd_phys = __hyp_pa(vm->pgt.pgd);
+
return 0;
}

void reclaim_guest_pages(struct pkvm_hyp_vm *vm)
{
+ void *pgd = vm->pgt.pgd;
unsigned long nr_pages;

nr_pages = kvm_pgtable_stage2_pgd_size(vm->kvm.arch.vtcr) >> PAGE_SHIFT;
- WARN_ON(__pkvm_hyp_donate_host(hyp_virt_to_pfn(vm->pgt.pgd), nr_pages));
+
+ guest_lock_component(vm);
+ kvm_pgtable_stage2_destroy(&vm->pgt);
+ vm->kvm.arch.mmu.pgd_phys = 0ULL;
+ guest_unlock_component(vm);
+
+ WARN_ON(__pkvm_hyp_donate_host(hyp_virt_to_pfn(pgd), nr_pages));
}

int __pkvm_prot_finalize(void)
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 4b24e9e1e96b..e500539933ca 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -658,7 +658,9 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
return -EINVAL;

phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
- if (phys_shift) {
+ if (is_protected_kvm_enabled()) {
+ phys_shift = kvm_ipa_limit;
+ } else if (phys_shift) {
if (phys_shift > kvm_ipa_limit ||
phys_shift < ARM64_MIN_PARANGE_BITS)
return -EINVAL;
--
2.37.2.789.g6183377224-goog