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Subject[PATCH v11 13/20] RISC-V: KVM: Implement stage2 page table programming
Date
This patch implements all required functions for programming
the stage2 page table for each Guest/VM.

At high-level, the flow of stage2 related functions is similar
from KVM ARM/ARM64 implementation but the stage2 page table
format is quite different for 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>
---
arch/riscv/include/asm/kvm_host.h | 10 +
arch/riscv/include/asm/pgtable-bits.h | 1 +
arch/riscv/kvm/mmu.c | 565 +++++++++++++++++++++++++-
3 files changed, 566 insertions(+), 10 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 35a291493f05..dd1acb011fff 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -73,6 +73,13 @@ struct kvm_mmio_decode {
int return_handled;
};

+#define KVM_MMU_PAGE_CACHE_NR_OBJS 32
+
+struct kvm_mmu_page_cache {
+ int nobjs;
+ void *objects[KVM_MMU_PAGE_CACHE_NR_OBJS];
+};
+
struct kvm_cpu_context {
unsigned long zero;
unsigned long ra;
@@ -164,6 +171,9 @@ struct kvm_vcpu_arch {
/* MMIO instruction details */
struct kvm_mmio_decode mmio_decode;

+ /* Cache pages needed to program page tables with spinlock held */
+ struct kvm_mmu_page_cache mmu_page_cache;
+
/* VCPU power-off state */
bool power_off;

diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
index bbaeb5d35842..be49d62fcc2b 100644
--- a/arch/riscv/include/asm/pgtable-bits.h
+++ b/arch/riscv/include/asm/pgtable-bits.h
@@ -26,6 +26,7 @@

#define _PAGE_SPECIAL _PAGE_SOFT
#define _PAGE_TABLE _PAGE_PRESENT
+#define _PAGE_LEAF (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC)

/*
* _PAGE_PROT_NONE is set on not-present pages (and ignored by the hardware) to
diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
index 2b965f9aac07..f491c6aa4502 100644
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -17,6 +17,357 @@
#include <linux/sched/signal.h>
#include <asm/page.h>
#include <asm/pgtable.h>
+#include <asm/sbi.h>
+
+#ifdef CONFIG_64BIT
+#define stage2_have_pmd true
+#define stage2_gpa_size ((phys_addr_t)(1ULL << 39))
+#define stage2_pgd_levels 3
+#define stage2_index_bits 9
+#else
+#define stage2_have_pmd false
+#define stage2_gpa_size ((phys_addr_t)(1ULL << 32))
+#define stage2_pgd_levels 2
+#define stage2_index_bits 10
+#endif
+
+#define stage2_pte_index(addr, level) \
+(((addr) >> (PAGE_SHIFT + stage2_index_bits * (level))) & (PTRS_PER_PTE - 1))
+
+static inline unsigned long stage2_pte_page_vaddr(pte_t pte)
+{
+ return (unsigned long)pfn_to_virt(pte_val(pte) >> _PAGE_PFN_SHIFT);
+}
+
+static int stage2_page_size_to_level(unsigned long page_size, u32 *out_level)
+{
+ if (page_size == PAGE_SIZE)
+ *out_level = 0;
+ else if (page_size == PMD_SIZE)
+ *out_level = 1;
+ else if (page_size == PGDIR_SIZE)
+ *out_level = (stage2_have_pmd) ? 2 : 1;
+ else
+ return -EINVAL;
+
+ return 0;
+}
+
+static int stage2_level_to_page_size(u32 level, unsigned long *out_pgsize)
+{
+ switch (level) {
+ case 0:
+ *out_pgsize = PAGE_SIZE;
+ break;
+ case 1:
+ *out_pgsize = (stage2_have_pmd) ? PMD_SIZE : PGDIR_SIZE;
+ break;
+ case 2:
+ *out_pgsize = PGDIR_SIZE;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int stage2_cache_topup(struct kvm_mmu_page_cache *pcache,
+ int min, int max)
+{
+ void *page;
+
+ BUG_ON(max > KVM_MMU_PAGE_CACHE_NR_OBJS);
+ if (pcache->nobjs >= min)
+ return 0;
+ while (pcache->nobjs < max) {
+ page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ return -ENOMEM;
+ pcache->objects[pcache->nobjs++] = page;
+ }
+
+ return 0;
+}
+
+static void stage2_cache_flush(struct kvm_mmu_page_cache *pcache)
+{
+ while (pcache && pcache->nobjs)
+ free_page((unsigned long)pcache->objects[--pcache->nobjs]);
+}
+
+static void *stage2_cache_alloc(struct kvm_mmu_page_cache *pcache)
+{
+ void *p;
+
+ if (!pcache)
+ return NULL;
+
+ BUG_ON(!pcache->nobjs);
+ p = pcache->objects[--pcache->nobjs];
+
+ return p;
+}
+
+static bool stage2_get_leaf_entry(struct kvm *kvm, gpa_t addr,
+ pte_t **ptepp, u32 *ptep_level)
+{
+ pte_t *ptep;
+ u32 current_level = stage2_pgd_levels - 1;
+
+ *ptep_level = current_level;
+ ptep = (pte_t *)kvm->arch.pgd;
+ ptep = &ptep[stage2_pte_index(addr, current_level)];
+ while (ptep && pte_val(*ptep)) {
+ if (pte_val(*ptep) & _PAGE_LEAF) {
+ *ptep_level = current_level;
+ *ptepp = ptep;
+ return true;
+ }
+
+ if (current_level) {
+ current_level--;
+ *ptep_level = current_level;
+ ptep = (pte_t *)stage2_pte_page_vaddr(*ptep);
+ ptep = &ptep[stage2_pte_index(addr, current_level)];
+ } else {
+ ptep = NULL;
+ }
+ }
+
+ return false;
+}
+
+static void stage2_remote_tlb_flush(struct kvm *kvm, u32 level, gpa_t addr)
+{
+ struct cpumask hmask;
+ unsigned long size = PAGE_SIZE;
+ struct kvm_vmid *vmid = &kvm->arch.vmid;
+
+ if (stage2_level_to_page_size(level, &size))
+ return;
+ addr &= ~(size - 1);
+
+ /*
+ * TODO: Instead of cpu_online_mask, we should only target CPUs
+ * where the Guest/VM is running.
+ */
+ preempt_disable();
+ riscv_cpuid_to_hartid_mask(cpu_online_mask, &hmask);
+ sbi_remote_hfence_gvma_vmid(cpumask_bits(&hmask), addr, size,
+ READ_ONCE(vmid->vmid));
+ preempt_enable();
+}
+
+static int stage2_set_pte(struct kvm *kvm, u32 level,
+ struct kvm_mmu_page_cache *pcache,
+ gpa_t addr, const pte_t *new_pte)
+{
+ u32 current_level = stage2_pgd_levels - 1;
+ pte_t *next_ptep = (pte_t *)kvm->arch.pgd;
+ pte_t *ptep = &next_ptep[stage2_pte_index(addr, current_level)];
+
+ if (current_level < level)
+ return -EINVAL;
+
+ while (current_level != level) {
+ if (pte_val(*ptep) & _PAGE_LEAF)
+ return -EEXIST;
+
+ if (!pte_val(*ptep)) {
+ next_ptep = stage2_cache_alloc(pcache);
+ if (!next_ptep)
+ return -ENOMEM;
+ *ptep = pfn_pte(PFN_DOWN(__pa(next_ptep)),
+ __pgprot(_PAGE_TABLE));
+ } else {
+ if (pte_val(*ptep) & _PAGE_LEAF)
+ return -EEXIST;
+ next_ptep = (pte_t *)stage2_pte_page_vaddr(*ptep);
+ }
+
+ current_level--;
+ ptep = &next_ptep[stage2_pte_index(addr, current_level)];
+ }
+
+ *ptep = *new_pte;
+ if (pte_val(*ptep) & _PAGE_LEAF)
+ stage2_remote_tlb_flush(kvm, current_level, addr);
+
+ return 0;
+}
+
+static int stage2_map_page(struct kvm *kvm,
+ struct kvm_mmu_page_cache *pcache,
+ gpa_t gpa, phys_addr_t hpa,
+ unsigned long page_size, pgprot_t prot)
+{
+ int ret;
+ u32 level = 0;
+ pte_t new_pte;
+
+ ret = stage2_page_size_to_level(page_size, &level);
+ if (ret)
+ return ret;
+
+ new_pte = pfn_pte(PFN_DOWN(hpa), prot);
+ return stage2_set_pte(kvm, level, pcache, gpa, &new_pte);
+}
+
+enum stage2_op {
+ STAGE2_OP_NOP = 0, /* Nothing */
+ STAGE2_OP_CLEAR, /* Clear/Unmap */
+ STAGE2_OP_WP, /* Write-protect */
+};
+
+static void stage2_op_pte(struct kvm *kvm, gpa_t addr,
+ pte_t *ptep, u32 ptep_level, enum stage2_op op)
+{
+ int i, ret;
+ pte_t *next_ptep;
+ u32 next_ptep_level;
+ unsigned long next_page_size, page_size;
+
+ ret = stage2_level_to_page_size(ptep_level, &page_size);
+ if (ret)
+ return;
+
+ BUG_ON(addr & (page_size - 1));
+
+ if (!pte_val(*ptep))
+ return;
+
+ if (ptep_level && !(pte_val(*ptep) & _PAGE_LEAF)) {
+ next_ptep = (pte_t *)stage2_pte_page_vaddr(*ptep);
+ next_ptep_level = ptep_level - 1;
+ ret = stage2_level_to_page_size(next_ptep_level,
+ &next_page_size);
+ if (ret)
+ return;
+
+ if (op == STAGE2_OP_CLEAR)
+ set_pte(ptep, __pte(0));
+ for (i = 0; i < PTRS_PER_PTE; i++)
+ stage2_op_pte(kvm, addr + i * next_page_size,
+ &next_ptep[i], next_ptep_level, op);
+ if (op == STAGE2_OP_CLEAR)
+ put_page(virt_to_page(next_ptep));
+ } else {
+ if (op == STAGE2_OP_CLEAR)
+ set_pte(ptep, __pte(0));
+ else if (op == STAGE2_OP_WP)
+ set_pte(ptep, __pte(pte_val(*ptep) & ~_PAGE_WRITE));
+ stage2_remote_tlb_flush(kvm, ptep_level, addr);
+ }
+}
+
+static void stage2_unmap_range(struct kvm *kvm, gpa_t start, gpa_t size)
+{
+ int ret;
+ pte_t *ptep;
+ u32 ptep_level;
+ bool found_leaf;
+ unsigned long page_size;
+ gpa_t addr = start, end = start + size;
+
+ while (addr < end) {
+ found_leaf = stage2_get_leaf_entry(kvm, addr,
+ &ptep, &ptep_level);
+ ret = stage2_level_to_page_size(ptep_level, &page_size);
+ if (ret)
+ break;
+
+ if (!found_leaf)
+ goto next;
+
+ if (!(addr & (page_size - 1)) && ((end - addr) >= page_size))
+ stage2_op_pte(kvm, addr, ptep,
+ ptep_level, STAGE2_OP_CLEAR);
+
+next:
+ addr += page_size;
+ }
+}
+
+static void stage2_wp_range(struct kvm *kvm, gpa_t start, gpa_t end)
+{
+ int ret;
+ pte_t *ptep;
+ u32 ptep_level;
+ bool found_leaf;
+ gpa_t addr = start;
+ unsigned long page_size;
+
+ while (addr < end) {
+ found_leaf = stage2_get_leaf_entry(kvm, addr,
+ &ptep, &ptep_level);
+ ret = stage2_level_to_page_size(ptep_level, &page_size);
+ if (ret)
+ break;
+
+ if (!found_leaf)
+ goto next;
+
+ if (!(addr & (page_size - 1)) && ((end - addr) >= page_size))
+ stage2_op_pte(kvm, addr, ptep,
+ ptep_level, STAGE2_OP_WP);
+
+next:
+ addr += page_size;
+ }
+}
+
+void stage2_wp_memory_region(struct kvm *kvm, int slot)
+{
+ struct kvm_memslots *slots = kvm_memslots(kvm);
+ struct kvm_memory_slot *memslot = id_to_memslot(slots, slot);
+ phys_addr_t start = memslot->base_gfn << PAGE_SHIFT;
+ phys_addr_t end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT;
+
+ spin_lock(&kvm->mmu_lock);
+ stage2_wp_range(kvm, start, end);
+ spin_unlock(&kvm->mmu_lock);
+ kvm_flush_remote_tlbs(kvm);
+}
+
+int stage2_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
+ unsigned long size, bool writable)
+{
+ pte_t pte;
+ int ret = 0;
+ unsigned long pfn;
+ phys_addr_t addr, end;
+ struct kvm_mmu_page_cache pcache = { 0, };
+
+ end = (gpa + size + PAGE_SIZE - 1) & PAGE_MASK;
+ pfn = __phys_to_pfn(hpa);
+
+ for (addr = gpa; addr < end; addr += PAGE_SIZE) {
+ pte = pfn_pte(pfn, PAGE_KERNEL);
+
+ if (!writable)
+ pte = pte_wrprotect(pte);
+
+ ret = stage2_cache_topup(&pcache,
+ stage2_pgd_levels,
+ KVM_MMU_PAGE_CACHE_NR_OBJS);
+ if (ret)
+ goto out;
+
+ spin_lock(&kvm->mmu_lock);
+ ret = stage2_set_pte(kvm, 0, &pcache, addr, &pte);
+ spin_unlock(&kvm->mmu_lock);
+ if (ret)
+ goto out;
+
+ pfn++;
+ }
+
+out:
+ stage2_cache_flush(&pcache);
+ return ret;
+
+}

void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
struct kvm_memory_slot *dont)
@@ -35,7 +386,7 @@ void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)

void kvm_arch_flush_shadow_all(struct kvm *kvm)
{
- /* TODO: */
+ kvm_riscv_stage2_free_pgd(kvm);
}

void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
@@ -49,7 +400,13 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
const struct kvm_memory_slot *new,
enum kvm_mr_change change)
{
- /* TODO: */
+ /*
+ * At this point memslot has been committed and there is an
+ * allocated dirty_bitmap[], dirty pages will be be tracked while the
+ * memory slot is write protected.
+ */
+ if (change != KVM_MR_DELETE && mem->flags & KVM_MEM_LOG_DIRTY_PAGES)
+ stage2_wp_memory_region(kvm, mem->slot);
}

int kvm_arch_prepare_memory_region(struct kvm *kvm,
@@ -57,34 +414,222 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
const struct kvm_userspace_memory_region *mem,
enum kvm_mr_change change)
{
- /* TODO: */
- return 0;
+ hva_t hva = mem->userspace_addr;
+ hva_t reg_end = hva + mem->memory_size;
+ bool writable = !(mem->flags & KVM_MEM_READONLY);
+ int ret = 0;
+
+ if (change != KVM_MR_CREATE && change != KVM_MR_MOVE &&
+ change != KVM_MR_FLAGS_ONLY)
+ return 0;
+
+ /*
+ * Prevent userspace from creating a memory region outside of the GPA
+ * space addressable by the KVM guest GPA space.
+ */
+ if ((memslot->base_gfn + memslot->npages) >=
+ (stage2_gpa_size >> PAGE_SHIFT))
+ return -EFAULT;
+
+ down_read(&current->mm->mmap_sem);
+
+ /*
+ * A memory region could potentially cover multiple VMAs, and
+ * any holes between them, so iterate over all of them to find
+ * out if we can map any of them right now.
+ *
+ * +--------------------------------------------+
+ * +---------------+----------------+ +----------------+
+ * | : VMA 1 | VMA 2 | | VMA 3 : |
+ * +---------------+----------------+ +----------------+
+ * | memory region |
+ * +--------------------------------------------+
+ */
+ do {
+ struct vm_area_struct *vma = find_vma(current->mm, hva);
+ hva_t vm_start, vm_end;
+
+ if (!vma || vma->vm_start >= reg_end)
+ break;
+
+ /*
+ * Mapping a read-only VMA is only allowed if the
+ * memory region is configured as read-only.
+ */
+ if (writable && !(vma->vm_flags & VM_WRITE)) {
+ ret = -EPERM;
+ break;
+ }
+
+ /* Take the intersection of this VMA with the memory region */
+ vm_start = max(hva, vma->vm_start);
+ vm_end = min(reg_end, vma->vm_end);
+
+ if (vma->vm_flags & VM_PFNMAP) {
+ gpa_t gpa = mem->guest_phys_addr +
+ (vm_start - mem->userspace_addr);
+ phys_addr_t pa;
+
+ pa = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
+ pa += vm_start - vma->vm_start;
+
+ /* IO region dirty page logging not allowed */
+ if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = stage2_ioremap(kvm, gpa, pa,
+ vm_end - vm_start, writable);
+ if (ret)
+ break;
+ }
+ hva = vm_end;
+ } while (hva < reg_end);
+
+ if (change == KVM_MR_FLAGS_ONLY)
+ goto out;
+
+ spin_lock(&kvm->mmu_lock);
+ if (ret)
+ stage2_unmap_range(kvm, mem->guest_phys_addr,
+ mem->memory_size);
+ spin_unlock(&kvm->mmu_lock);
+
+out:
+ up_read(&current->mm->mmap_sem);
+ return ret;
}

int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned long hva,
bool is_write)
{
- /* TODO: */
- return 0;
+ int ret;
+ short lsb;
+ kvm_pfn_t hfn;
+ bool writeable;
+ gfn_t gfn = gpa >> PAGE_SHIFT;
+ 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;
+
+ down_read(&current->mm->mmap_sem);
+
+ vma = find_vma_intersection(current->mm, hva, hva + 1);
+ if (unlikely(!vma)) {
+ kvm_err("Failed to find VMA for hva 0x%lx\n", hva);
+ up_read(&current->mm->mmap_sem);
+ return -EFAULT;
+ }
+
+ vma_pagesize = vma_kernel_pagesize(vma);
+
+ if (vma_pagesize == PMD_SIZE || vma_pagesize == PGDIR_SIZE)
+ gfn = (gpa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT;
+
+ up_read(&current->mm->mmap_sem);
+
+ if (vma_pagesize != PGDIR_SIZE &&
+ vma_pagesize != PMD_SIZE &&
+ vma_pagesize != PAGE_SIZE) {
+ kvm_err("Invalid VMA page size 0x%lx\n", vma_pagesize);
+ return -EFAULT;
+ }
+
+ /* We need minimum second+third level pages */
+ ret = stage2_cache_topup(pcache, stage2_pgd_levels,
+ KVM_MMU_PAGE_CACHE_NR_OBJS);
+ if (ret) {
+ kvm_err("Failed to topup stage2 cache\n");
+ return ret;
+ }
+
+ hfn = gfn_to_pfn_prot(kvm, gfn, is_write, &writeable);
+ if (hfn == KVM_PFN_ERR_HWPOISON) {
+ if (is_vm_hugetlb_page(vma))
+ lsb = huge_page_shift(hstate_vma(vma));
+ else
+ lsb = PAGE_SHIFT;
+
+ send_sig_mceerr(BUS_MCEERR_AR, (void __user *)hva,
+ lsb, current);
+ return 0;
+ }
+ if (is_error_noslot_pfn(hfn))
+ return -EFAULT;
+ if (!writeable && is_write)
+ return -EPERM;
+
+ spin_lock(&kvm->mmu_lock);
+
+ if (writeable) {
+ kvm_set_pfn_dirty(hfn);
+ ret = stage2_map_page(kvm, pcache, gpa, hfn << PAGE_SHIFT,
+ vma_pagesize, PAGE_WRITE_EXEC);
+ } else {
+ ret = stage2_map_page(kvm, pcache, gpa, hfn << PAGE_SHIFT,
+ vma_pagesize, PAGE_READ_EXEC);
+ }
+
+ if (ret)
+ kvm_err("Failed to map in stage2\n");
+
+ spin_unlock(&kvm->mmu_lock);
+ kvm_set_pfn_accessed(hfn);
+ kvm_release_pfn_clean(hfn);
+ return ret;
}

void kvm_riscv_stage2_flush_cache(struct kvm_vcpu *vcpu)
{
- /* TODO: */
+ stage2_cache_flush(&vcpu->arch.mmu_page_cache);
}

int kvm_riscv_stage2_alloc_pgd(struct kvm *kvm)
{
- /* TODO: */
+ if (kvm->arch.pgd != NULL) {
+ kvm_err("kvm_arch already initialized?\n");
+ return -EINVAL;
+ }
+
+ kvm->arch.pgd = alloc_pages_exact(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
+ if (!kvm->arch.pgd)
+ return -ENOMEM;
+ kvm->arch.pgd_phys = virt_to_phys(kvm->arch.pgd);
+
return 0;
}

void kvm_riscv_stage2_free_pgd(struct kvm *kvm)
{
- /* TODO: */
+ void *pgd = NULL;
+
+ spin_lock(&kvm->mmu_lock);
+ if (kvm->arch.pgd) {
+ stage2_unmap_range(kvm, 0UL, stage2_gpa_size);
+ pgd = READ_ONCE(kvm->arch.pgd);
+ kvm->arch.pgd = NULL;
+ kvm->arch.pgd_phys = 0;
+ }
+ spin_unlock(&kvm->mmu_lock);
+
+ /* Free the HW pgd, one page at a time */
+ if (pgd)
+ free_pages_exact(pgd, PAGE_SIZE);
}

void kvm_riscv_stage2_update_hgatp(struct kvm_vcpu *vcpu)
{
- /* TODO: */
+ unsigned long hgatp = HGATP_MODE;
+ struct kvm_arch *k = &vcpu->kvm->arch;
+
+ hgatp |= (READ_ONCE(k->vmid.vmid) << HGATP_VMID_SHIFT) &
+ HGATP_VMID_MASK;
+ hgatp |= (k->pgd_phys >> PAGE_SHIFT) & HGATP_PPN;
+
+ csr_write(CSR_HGATP, hgatp);
+
+ if (!kvm_riscv_stage2_vmid_bits())
+ __kvm_riscv_hfence_gvma_all();
}
--
2.17.1
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