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Subject[PATCH v7 14/21] RISC-V: KVM: Implement MMU notifiers
Date
This patch implements MMU notifiers for KVM RISC-V so that Guest
physical address space is in-sync with Host physical address space.

This will allow swapping, page migration, etc to work transparently
with KVM RISC-V.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Alexander Graf <graf@amazon.com>
---
arch/riscv/include/asm/kvm_host.h | 7 ++
arch/riscv/kvm/Kconfig | 1 +
arch/riscv/kvm/mmu.c | 200 +++++++++++++++++++++++++++++-
arch/riscv/kvm/vm.c | 1 +
4 files changed, 208 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index bc27f664b443..79ceb2aa8ae6 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -193,6 +193,13 @@ static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
int kvm_riscv_setup_vsip(void);
void kvm_riscv_cleanup_vsip(void);

+#define KVM_ARCH_WANT_MMU_NOTIFIER
+int kvm_unmap_hva_range(struct kvm *kvm,
+ unsigned long start, unsigned long end);
+int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
+int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
+
void __kvm_riscv_hfence_gvma_vmid_gpa(unsigned long vmid,
unsigned long gpa);
void __kvm_riscv_hfence_gvma_vmid(unsigned long vmid);
diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
index 35fd30d0e432..002e14ee37f6 100644
--- a/arch/riscv/kvm/Kconfig
+++ b/arch/riscv/kvm/Kconfig
@@ -20,6 +20,7 @@ if VIRTUALIZATION
config KVM
tristate "Kernel-based Virtual Machine (KVM) support"
depends on OF
+ select MMU_NOTIFIER
select PREEMPT_NOTIFIERS
select ANON_INODES
select KVM_MMIO
diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
index 590669290139..d8a692d3e640 100644
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -67,6 +67,66 @@ static void *stage2_cache_alloc(struct kvm_mmu_page_cache *pcache)
return p;
}

+static int stage2_pgdp_test_and_clear_young(pgd_t *pgd)
+{
+ return ptep_test_and_clear_young(NULL, 0, (pte_t *)pgd);
+}
+
+static int stage2_pmdp_test_and_clear_young(pmd_t *pmd)
+{
+ return ptep_test_and_clear_young(NULL, 0, (pte_t *)pmd);
+}
+
+static int stage2_ptep_test_and_clear_young(pte_t *pte)
+{
+ return ptep_test_and_clear_young(NULL, 0, pte);
+}
+
+static bool stage2_get_leaf_entry(struct kvm *kvm, gpa_t addr,
+ pgd_t **pgdpp, pmd_t **pmdpp, pte_t **ptepp)
+{
+ pgd_t *pgdp;
+ pmd_t *pmdp;
+ pte_t *ptep;
+
+ *pgdpp = NULL;
+ *pmdpp = NULL;
+ *ptepp = NULL;
+
+ pgdp = &kvm->arch.pgd[pgd_index(addr)];
+ if (!pgd_val(*pgdp))
+ return false;
+ if (pgd_val(*pgdp) & _PAGE_LEAF) {
+ *pgdpp = pgdp;
+ return true;
+ }
+
+ if (stage2_have_pmd) {
+ pmdp = (void *)pgd_page_vaddr(*pgdp);
+ pmdp = &pmdp[pmd_index(addr)];
+ if (!pmd_present(*pmdp))
+ return false;
+ if (pmd_val(*pmdp) & _PAGE_LEAF) {
+ *pmdpp = pmdp;
+ return true;
+ }
+
+ ptep = (void *)pmd_page_vaddr(*pmdp);
+ } else {
+ ptep = (void *)pgd_page_vaddr(*pgdp);
+ }
+
+ ptep = &ptep[pte_index(addr)];
+ if (!pte_present(*ptep))
+ return false;
+ if (pte_val(*ptep) & _PAGE_LEAF) {
+ *ptepp = ptep;
+ return true;
+ }
+
+ return false;
+}
+
struct local_guest_tlb_info {
struct kvm_vmid *vmid;
gpa_t addr;
@@ -450,6 +510,38 @@ int stage2_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,

}

+static int handle_hva_to_gpa(struct kvm *kvm,
+ unsigned long start,
+ unsigned long end,
+ int (*handler)(struct kvm *kvm,
+ gpa_t gpa, u64 size,
+ void *data),
+ void *data)
+{
+ struct kvm_memslots *slots;
+ struct kvm_memory_slot *memslot;
+ int ret = 0;
+
+ slots = kvm_memslots(kvm);
+
+ /* we only care about the pages that the guest sees */
+ kvm_for_each_memslot(memslot, slots) {
+ unsigned long hva_start, hva_end;
+ gfn_t gpa;
+
+ hva_start = max(start, memslot->userspace_addr);
+ hva_end = min(end, memslot->userspace_addr +
+ (memslot->npages << PAGE_SHIFT));
+ if (hva_start >= hva_end)
+ continue;
+
+ gpa = hva_to_gfn_memslot(hva_start, memslot) << PAGE_SHIFT;
+ ret |= handler(kvm, gpa, (u64)(hva_end - hva_start), data);
+ }
+
+ return ret;
+}
+
void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
struct kvm_memory_slot *dont)
{
@@ -582,6 +674,106 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
return ret;
}

+static int kvm_unmap_hva_handler(struct kvm *kvm,
+ gpa_t gpa, u64 size, void *data)
+{
+ stage2_unmap_range(kvm, gpa, size);
+ return 0;
+}
+
+int kvm_unmap_hva_range(struct kvm *kvm,
+ unsigned long start, unsigned long end)
+{
+ if (!kvm->arch.pgd)
+ return 0;
+
+ handle_hva_to_gpa(kvm, start, end,
+ &kvm_unmap_hva_handler, NULL);
+ return 0;
+}
+
+static int kvm_set_spte_handler(struct kvm *kvm,
+ gpa_t gpa, u64 size, void *data)
+{
+ pte_t *pte = (pte_t *)data;
+
+ WARN_ON(size != PAGE_SIZE);
+ stage2_set_pte(kvm, NULL, gpa, pte);
+
+ return 0;
+}
+
+int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
+{
+ unsigned long end = hva + PAGE_SIZE;
+ kvm_pfn_t pfn = pte_pfn(pte);
+ pte_t stage2_pte;
+
+ if (!kvm->arch.pgd)
+ return 0;
+
+ stage2_pte = pfn_pte(pfn, PAGE_WRITE_EXEC);
+ handle_hva_to_gpa(kvm, hva, end,
+ &kvm_set_spte_handler, &stage2_pte);
+
+ return 0;
+}
+
+static int kvm_age_hva_handler(struct kvm *kvm,
+ gpa_t gpa, u64 size, void *data)
+{
+ pgd_t *pgd;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PGDIR_SIZE);
+ if (!stage2_get_leaf_entry(kvm, gpa, &pgd, &pmd, &pte))
+ return 0;
+
+ if (pgd)
+ return stage2_pgdp_test_and_clear_young(pgd);
+ else if (pmd)
+ return stage2_pmdp_test_and_clear_young(pmd);
+ else
+ return stage2_ptep_test_and_clear_young(pte);
+}
+
+int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
+{
+ if (!kvm->arch.pgd)
+ return 0;
+
+ return handle_hva_to_gpa(kvm, start, end, kvm_age_hva_handler, NULL);
+}
+
+static int kvm_test_age_hva_handler(struct kvm *kvm,
+ gpa_t gpa, u64 size, void *data)
+{
+ pgd_t *pgd;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ WARN_ON(size != PAGE_SIZE && size != PMD_SIZE);
+ if (!stage2_get_leaf_entry(kvm, gpa, &pgd, &pmd, &pte))
+ return 0;
+
+ if (pgd)
+ return pte_young(*((pte_t *)pgd));
+ else if (pmd)
+ return pte_young(*((pte_t *)pmd));
+ else
+ return pte_young(*pte);
+}
+
+int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
+{
+ if (!kvm->arch.pgd)
+ return 0;
+
+ return handle_hva_to_gpa(kvm, hva, hva,
+ kvm_test_age_hva_handler, NULL);
+}
+
int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned long hva,
bool is_write)
{
@@ -593,7 +785,7 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned long hva,
struct vm_area_struct *vma;
struct kvm *kvm = vcpu->kvm;
struct kvm_mmu_page_cache *pcache = &vcpu->arch.mmu_page_cache;
- unsigned long vma_pagesize;
+ unsigned long vma_pagesize, mmu_seq;

down_read(&current->mm->mmap_sem);

@@ -623,6 +815,8 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned long hva,
return ret;
}

+ mmu_seq = kvm->mmu_notifier_seq;
+
hfn = gfn_to_pfn_prot(kvm, gfn, is_write, &writeable);
if (hfn == KVM_PFN_ERR_HWPOISON) {
if (is_vm_hugetlb_page(vma))
@@ -641,6 +835,9 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned long hva,

spin_lock(&kvm->mmu_lock);

+ if (mmu_notifier_retry(kvm, mmu_seq))
+ goto out_unlock;
+
if (writeable) {
kvm_set_pfn_dirty(hfn);
ret = stage2_map_page(kvm, pcache, gpa, hfn << PAGE_SHIFT,
@@ -653,6 +850,7 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned long hva,
if (ret)
kvm_err("Failed to map in stage2\n");

+out_unlock:
spin_unlock(&kvm->mmu_lock);
kvm_set_pfn_accessed(hfn);
kvm_release_pfn_clean(hfn);
diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index c5aab5478c38..fd84b4d914dc 100644
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -54,6 +54,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
switch (ext) {
case KVM_CAP_DEVICE_CTRL:
case KVM_CAP_USER_MEMORY:
+ case KVM_CAP_SYNC_MMU:
case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
case KVM_CAP_ONE_REG:
case KVM_CAP_READONLY_MEM:
--
2.17.1
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