On Thu, 2021-12-09 at 19:34 +0100, Paolo Bonzini wrote:
> Sorry for the late review...
NP, very useful fixes. Thanks. Incremental patch looks like this. It
passes the xen_shinfo_test self-test; will test it with real Xen guests
tomorrow and repost based on your kvm/next tree once it shows up.
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index d8c6e1d4a647..9e3c662f815f 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -124,6 +124,33 @@ static void __release_gpc(struct kvm *kvm, kvm_pfn_t pfn, void *khva,
}
}
+static kvm_pfn_t hva_to_pfn_retry(struct kvm *kvm, unsigned long uhva)
+{
+ unsigned long mmu_seq;
+ kvm_pfn_t new_pfn;
+ int retry;
+
+ do {
+ mmu_seq = kvm->mmu_notifier_seq;
+ smp_rmb();
+
+ /* We always request a writeable mapping */
+ new_pfn = hva_to_pfn(uhva, false, NULL, true, NULL);
+ if (is_error_noslot_pfn(new_pfn))
+ break;
+
+ KVM_MMU_READ_LOCK(kvm);
+ retry = mmu_notifier_retry_hva(kvm, mmu_seq, uhva);
+ KVM_MMU_READ_UNLOCK(kvm);
+ if (!retry)
+ break;
+
+ cond_resched();
+ } while (1);
+
+ return new_pfn;
+}
+
int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
gpa_t gpa, unsigned long len, bool dirty)
{
@@ -147,7 +174,7 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
old_gpa = gpc->gpa;
old_pfn = gpc->pfn;
- old_khva = gpc->khva;
+ old_khva = (void *)((unsigned long)gpc->khva & ~PAGE_MASK);
old_uhva = gpc->uhva;
old_valid = gpc->valid;
old_dirty = gpc->dirty;
@@ -178,8 +205,6 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
if (!old_valid || old_uhva != gpc->uhva) {
unsigned long uhva = gpc->uhva;
void *new_khva = NULL;
- unsigned long mmu_seq;
- int retry;
/* Placeholders for "hva is valid but not yet mapped" */
gpc->pfn = KVM_PFN_ERR_FAULT;
@@ -188,28 +213,15 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
write_unlock_irq(&gpc->lock);
- retry_map:
- mmu_seq = kvm->mmu_notifier_seq;
- smp_rmb();
-
- /* We always request a writeable mapping */
- new_pfn = hva_to_pfn(uhva, false, NULL, true, NULL);
+ new_pfn = hva_to_pfn_retry(kvm, uhva);
if (is_error_noslot_pfn(new_pfn)) {
ret = -EFAULT;
goto map_done;
}
- KVM_MMU_READ_LOCK(kvm);
- retry = mmu_notifier_retry_hva(kvm, mmu_seq, uhva);
- KVM_MMU_READ_UNLOCK(kvm);
- if (retry) {
- cond_resched();
- goto retry_map;
- }
-
if (gpc->kernel_map) {
if (new_pfn == old_pfn) {
- new_khva = (void *)((unsigned long)old_khva - page_offset);
+ new_khva = old_khva;
old_pfn = KVM_PFN_ERR_FAULT;
old_khva = NULL;
} else if (pfn_valid(new_pfn)) {
@@ -219,7 +231,9 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
new_khva = memremap(pfn_to_hpa(new_pfn), PAGE_SIZE, MEMREMAP_WB);
#endif
}
- if (!new_khva)
+ if (new_khva)
+ new_khva += page_offset;
+ else
ret = -EFAULT;
}
@@ -232,7 +246,7 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
} else {
/* At this point, gpc->valid may already have been cleared */
gpc->pfn = new_pfn;
- gpc->khva = new_khva + page_offset;
+ gpc->khva = new_khva;
}
} else {
/* If the HVA→PFN mapping was already valid, don't unmap it. */
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