[PATCH v18 11/18] RISC-V: KVM: Implement MMU notifiers

Anup Patel
2021-05-19T03:37:26Z

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 | 2 +
arch/riscv/kvm/Kconfig | 1 +
arch/riscv/kvm/mmu.c | 90 +++++++++++++++++++++++++++++--
arch/riscv/kvm/vm.c | 1 +
4 files changed, 89 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index d2a7d299d67c..51fe663b5093 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -201,6 +201,8 @@ static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}

+#define KVM_ARCH_WANT_MMU_NOTIFIER
+
void __kvm_riscv_hfence_gvma_vmid_gpa(unsigned long gpa, unsigned long vmid);
void __kvm_riscv_hfence_gvma_vmid(unsigned long vmid);
void __kvm_riscv_hfence_gvma_gpa(unsigned long gpa);
diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
index 633063edaee8..a712bb910cda 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 (EXPERIMENTAL)"
depends on RISCV_SBI && MMU
+ 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 fcf9967f4b29..428bf8915a45 100644
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -300,7 +300,8 @@ static void stage2_op_pte(struct kvm *kvm, gpa_t addr,
}
}

-static void stage2_unmap_range(struct kvm *kvm, gpa_t start, gpa_t size)
+static void stage2_unmap_range(struct kvm *kvm, gpa_t start,
+ gpa_t size, bool may_block)
{
int ret;
pte_t *ptep;
@@ -325,6 +326,13 @@ static void stage2_unmap_range(struct kvm *kvm, gpa_t start, gpa_t size)

next:
addr += page_size;
+
+ /*
+ * If the range is too large, release the kvm->mmu_lock
+ * to prevent starvation and lockup detector warnings.
+ */
+ if (may_block && addr < end)
+ cond_resched_lock(&kvm->mmu_lock);
}
}

@@ -405,7 +413,6 @@ static int stage2_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
out:
stage2_cache_flush(&pcache);
return ret;
-
}

void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
@@ -547,7 +554,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
spin_lock(&kvm->mmu_lock);
if (ret)
stage2_unmap_range(kvm, mem->guest_phys_addr,
- mem->memory_size);
+ mem->memory_size, false);
spin_unlock(&kvm->mmu_lock);

out:
@@ -555,6 +562,73 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
return ret;
}

+bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
+{
+ if (!kvm->arch.pgd)
+ return 0;
+
+ stage2_unmap_range(kvm, range->start << PAGE_SHIFT,
+ (range->end - range->start) << PAGE_SHIFT,
+ range->may_block);
+ return 0;
+}
+
+bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
+{
+ int ret;
+ kvm_pfn_t pfn = pte_pfn(range->pte);
+
+ if (!kvm->arch.pgd)
+ return 0;
+
+ WARN_ON(range->end - range->start != 1);
+
+ ret = stage2_map_page(kvm, NULL, range->start << PAGE_SHIFT,
+ __pfn_to_phys(pfn), PAGE_SIZE, true, true);
+ if (ret) {
+ kvm_err("Failed to map stage2 page (error %d)\n", ret);
+ return 1;
+ }
+
+ return 0;
+}
+
+bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
+{
+ pte_t *ptep;
+ u32 ptep_level = 0;
+ u64 size = (range->end - range->start) << PAGE_SHIFT;
+
+ if (!kvm->arch.pgd)
+ return 0;
+
+ WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PGDIR_SIZE);
+
+ if (!stage2_get_leaf_entry(kvm, range->start << PAGE_SHIFT,
+ &ptep, &ptep_level))
+ return 0;
+
+ return ptep_test_and_clear_young(NULL, 0, ptep);
+}
+
+bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
+{
+ pte_t *ptep;
+ u32 ptep_level = 0;
+ u64 size = (range->end - range->start) << PAGE_SHIFT;
+
+ if (!kvm->arch.pgd)
+ return 0;
+
+ WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PGDIR_SIZE);
+
+ if (!stage2_get_leaf_entry(kvm, range->start << PAGE_SHIFT,
+ &ptep, &ptep_level))
+ return 0;
+
+ return pte_young(*ptep);
+}
+
int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,
struct kvm_memory_slot *memslot,
gpa_t gpa, unsigned long hva, bool is_write)
@@ -569,7 +643,7 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,
struct kvm_mmu_page_cache *pcache = &vcpu->arch.mmu_page_cache;
bool logging = (memslot->dirty_bitmap &&
!(memslot->flags & KVM_MEM_READONLY)) ? true : false;
- unsigned long vma_pagesize;
+ unsigned long vma_pagesize, mmu_seq;

mmap_read_lock(current->mm);

@@ -608,6 +682,8 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,
return ret;
}

+ mmu_seq = kvm->mmu_notifier_seq;
+
hfn = gfn_to_pfn_prot(kvm, gfn, is_write, &writeable);
if (hfn == KVM_PFN_ERR_HWPOISON) {
send_sig_mceerr(BUS_MCEERR_AR, (void __user *)hva,
@@ -626,6 +702,9 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,

spin_lock(&kvm->mmu_lock);

+ if (mmu_notifier_retry(kvm, mmu_seq))
+ goto out_unlock;
+
if (writeable) {
kvm_set_pfn_dirty(hfn);
mark_page_dirty(kvm, gfn);
@@ -639,6 +718,7 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,
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);
@@ -675,7 +755,7 @@ void kvm_riscv_stage2_free_pgd(struct kvm *kvm)

spin_lock(&kvm->mmu_lock);
if (kvm->arch.pgd) {
- stage2_unmap_range(kvm, 0UL, stage2_gpa_size);
+ stage2_unmap_range(kvm, 0UL, stage2_gpa_size, false);
pgd = READ_ONCE(kvm->arch.pgd);
kvm->arch.pgd = NULL;
kvm->arch.pgd_phys = 0;
diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index 6cde69a82252..00a1a88008be 100644
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -49,6 +49,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_IOEVENTFD:
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:
--
2.25.1