This changes the hypervisor page fault handler for radix guests to use
the generic KVM __gfn_to_pfn_memslot() function instead of using
get_user_pages_fast() and then handling the case of VM_PFNMAP vmas
specially. The old code missed the case of VM_IO vmas; with this
change, VM_IO vmas will now be handled correctly by code within
__gfn_to_pfn_memslot.
Currently, __gfn_to_pfn_memslot calls hva_to_pfn, which only uses
__get_user_pages_fast for the initial lookup in the cases where
either atomic or async is set. Since we are not setting either
atomic or async, we do our own __get_user_pages_fast first, for now.
This also adds code to check for the KVM_MEM_READONLY flag on the
memslot. If it is set and this is a write access, we synthesize a
data storage interrupt for the guest.
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
---
arch/powerpc/kvm/book3s_64_mmu_radix.c | 117 +++++++++++++++++----------------
1 file changed, 59 insertions(+), 58 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 05acc67..6c71aa2 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -392,11 +392,11 @@ int kvmppc_book3s_radix_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
unsigned long mmu_seq, pte_size;
unsigned long gpa, gfn, hva, pfn;
struct kvm_memory_slot *memslot;
- struct page *page = NULL, *pages[1];
- long ret, npages;
- unsigned int writing;
- struct vm_area_struct *vma;
- unsigned long flags;
+ struct page *page = NULL;
+ long ret;
+ bool writing;
+ bool upgrade_write = false;
+ bool *upgrade_p = &upgrade_write;
pte_t pte, *ptep;
unsigned long pgflags;
unsigned int shift, level;
@@ -436,12 +436,17 @@ int kvmppc_book3s_radix_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
dsisr & DSISR_ISSTORE);
}
- /* used to check for invalidations in progress */
- mmu_seq = kvm->mmu_notifier_seq;
- smp_rmb();
-
writing = (dsisr & DSISR_ISSTORE) != 0;
- hva = gfn_to_hva_memslot(memslot, gfn);
+ if (memslot->flags & KVM_MEM_READONLY) {
+ if (writing) {
+ /* give the guest a DSI */
+ dsisr = DSISR_ISSTORE | DSISR_PROTFAULT;
+ kvmppc_core_queue_data_storage(vcpu, ea, dsisr);
+ return RESUME_GUEST;
+ }
+ upgrade_p = NULL;
+ }
+
if (dsisr & DSISR_SET_RC) {
/*
* Need to set an R or C bit in the 2nd-level tables;
@@ -470,62 +475,58 @@ int kvmppc_book3s_radix_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
return RESUME_GUEST;
}
- ret = -EFAULT;
- pfn = 0;
- pte_size = PAGE_SIZE;
- pgflags = _PAGE_READ | _PAGE_EXEC;
- level = 0;
- npages = get_user_pages_fast(hva, 1, writing, pages);
- if (npages < 1) {
- /* Check if it's an I/O mapping */
- down_read(¤t->mm->mmap_sem);
- vma = find_vma(current->mm, hva);
- if (vma && vma->vm_start <= hva && hva < vma->vm_end &&
- (vma->vm_flags & VM_PFNMAP)) {
- pfn = vma->vm_pgoff +
- ((hva - vma->vm_start) >> PAGE_SHIFT);
- pgflags = pgprot_val(vma->vm_page_prot);
- }
- up_read(¤t->mm->mmap_sem);
- if (!pfn)
- return -EFAULT;
- } else {
- page = pages[0];
+ /* used to check for invalidations in progress */
+ mmu_seq = kvm->mmu_notifier_seq;
+ smp_rmb();
+
+ /*
+ * Do a fast check first, since __gfn_to_pfn_memslot doesn't
+ * do it with !atomic && !async, which is how we call it.
+ * We always ask for write permission since the common case
+ * is that the page is writable.
+ */
+ hva = gfn_to_hva_memslot(memslot, gfn);
+ if (upgrade_p && __get_user_pages_fast(hva, 1, 1, &page) == 1) {
pfn = page_to_pfn(page);
- if (PageCompound(page)) {
- pte_size <<= compound_order(compound_head(page));
- /* See if we can insert a 1GB or 2MB large PTE here */
- if (pte_size >= PUD_SIZE &&
- (gpa & (PUD_SIZE - PAGE_SIZE)) ==
- (hva & (PUD_SIZE - PAGE_SIZE))) {
- level = 2;
- pfn &= ~((PUD_SIZE >> PAGE_SHIFT) - 1);
- } else if (pte_size >= PMD_SIZE &&
- (gpa & (PMD_SIZE - PAGE_SIZE)) ==
- (hva & (PMD_SIZE - PAGE_SIZE))) {
- level = 1;
- pfn &= ~((PMD_SIZE >> PAGE_SHIFT) - 1);
- }
+ upgrade_write = true;
+ } else {
+ /* Call KVM generic code to do the slow-path check */
+ pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
+ writing, upgrade_p);
+ if (is_error_noslot_pfn(pfn))
+ return -EFAULT;
+ page = NULL;
+ if (pfn_valid(pfn)) {
+ page = pfn_to_page(pfn);
+ if (PageReserved(page))
+ page = NULL;
}
- /* See if we can provide write access */
- if (writing) {
- pgflags |= _PAGE_WRITE;
- } else {
- local_irq_save(flags);
- ptep = find_current_mm_pte(current->mm->pgd,
- hva, NULL, NULL);
- if (ptep && pte_write(*ptep))
- pgflags |= _PAGE_WRITE;
- local_irq_restore(flags);
+ }
+
+ /* See if we can insert a 1GB or 2MB large PTE here */
+ level = 0;
+ if (page && PageCompound(page)) {
+ pte_size = PAGE_SIZE << compound_order(compound_head(page));
+ if (pte_size >= PUD_SIZE &&
+ (gpa & (PUD_SIZE - PAGE_SIZE)) ==
+ (hva & (PUD_SIZE - PAGE_SIZE))) {
+ level = 2;
+ pfn &= ~((PUD_SIZE >> PAGE_SHIFT) - 1);
+ } else if (pte_size >= PMD_SIZE &&
+ (gpa & (PMD_SIZE - PAGE_SIZE)) ==
+ (hva & (PMD_SIZE - PAGE_SIZE))) {
+ level = 1;
+ pfn &= ~((PMD_SIZE >> PAGE_SHIFT) - 1);
}
}
/*
* Compute the PTE value that we need to insert.
*/
- pgflags |= _PAGE_PRESENT | _PAGE_PTE | _PAGE_ACCESSED;
- if (pgflags & _PAGE_WRITE)
- pgflags |= _PAGE_DIRTY;
+ pgflags = _PAGE_READ | _PAGE_EXEC | _PAGE_PRESENT | _PAGE_PTE |
+ _PAGE_ACCESSED;
+ if (writing || upgrade_write)
+ pgflags |= _PAGE_WRITE | _PAGE_DIRTY;
pte = pfn_pte(pfn, __pgprot(pgflags));
/* Allocate space in the tree and write the PTE */
--
2.7.4
--
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