KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA

Some cached pages may actually be overlays on guest memory that have a
fixed HVA within the VMM. It's pointless to invalidate such cached
mappings if the overlay is moved so allow a cache to be activated directly
with the HVA to cater for such cases. A subsequent patch will make use
of this facility.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
v8:
 - Re-worked to avoid messing with struct gfn_to_pfn_cache.

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b1dc2e5a64f3ee791159f7a38736740be3795838..484c587e8290e653bd26a601839585cb4cb50ae5 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1312,6 +1312,22 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm);
  */
 int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
 
+/**
+ * kvm_gpc_activate_hva - prepare a cached kernel mapping and HPA for a given HVA.
+ *
+ * @gpc:          struct gfn_to_pfn_cache object.
+ * @hva:          userspace virtual address to map.
+ * @len:          sanity check; the range being access must fit a single page.
+ *
+ * @return:       0 for success.
+ *                -EINVAL for a mapping which would cross a page boundary.
+ *                -EFAULT for an untranslatable guest physical address.
+ *
+ * The semantics of this function are the same as those of kvm_gpc_activate(). It
+ * merely bypasses a layer of address translation.
+ */
+int kvm_gpc_activate_hva(struct gfn_to_pfn_cache *gpc, unsigned long hva, unsigned long len);
+
 /**
  * kvm_gpc_check - check validity of a gfn_to_pfn_cache.
  *
@@ -1365,7 +1381,8 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
  */
 static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
 {
-       mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
+       if (gpc->gpa != KVM_XEN_INVALID_GPA)
+               mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
 }
 
 void kvm_sigset_activate(struct kvm_vcpu *vcpu);

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 610ff72fb631eef3a906c753223bd94e57711ab8..e0ffb6696cf202c1d6ae124613cccaf05bdf6a64 100644 (file)
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -210,11 +210,11 @@ out_error:
        return -EFAULT;
 }
 
-static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
+static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, u64 addr, bool addr_is_gpa,
                             unsigned long len)
 {
        struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
-       unsigned long page_offset = offset_in_page(gpa);
+       unsigned long page_offset = offset_in_page(addr);
        bool unmap_old = false;
        unsigned long old_page_offset;
        kvm_pfn_t old_pfn;
@@ -247,29 +247,42 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
        old_page_offset = offset_in_page(gpc->khva);
        old_khva = gpc->khva - old_page_offset;
 
-       /* If the userspace HVA is invalid, refresh that first */
-       if (gpc->gpa != gpa || gpc->generation != slots->generation ||
-           kvm_is_error_hva(gpc->uhva)) {
-               gfn_t gfn = gpa_to_gfn(gpa);
+       if (addr_is_gpa) {
+               if (gpc->gpa != addr ||
+                   gpc->generation != slots->generation ||
+                   kvm_is_error_hva(gpc->uhva)) {
+                       gfn_t gfn = gpa_to_gfn(addr);
 
-               gpc->gpa = gpa;
-               gpc->generation = slots->generation;
-               gpc->memslot = __gfn_to_memslot(slots, gfn);
-               gpc->uhva = gfn_to_hva_memslot(gpc->memslot, gfn);
+                       gpc->gpa = addr;
+                       gpc->generation = slots->generation;
+                       gpc->memslot = __gfn_to_memslot(slots, gfn);
+                       gpc->uhva = gfn_to_hva_memslot(gpc->memslot, gfn);
 
-               if (kvm_is_error_hva(gpc->uhva)) {
-                       ret = -EFAULT;
-                       goto out;
-               }
+                       if (kvm_is_error_hva(gpc->uhva)) {
+                               ret = -EFAULT;
+                               goto out;
+                       }
 
-               hva_change = true;
+                       hva_change = true;
+               } else {
+                       /*
+                        * No need to do any re-mapping if the only thing that has
+                        * changed is the page offset. Just subtract the old offset
+                        * before the new one is added in.
+                        */
+                       gpc->uhva -= old_page_offset;
+               }
        } else {
-               /*
-                * No need to do any re-mapping if the only thing that has
-                * changed is the page offset. Just subtract the old offset
-                * before the new one is added in.
-                */
+               gpc->gpa = KVM_XEN_INVALID_GPA;
+
+               /* Align to page boundary before checking for a change */
                gpc->uhva -= old_page_offset;
+               addr -= page_offset;
+
+               if (gpc->uhva != addr) {
+                       gpc->uhva = addr;
+                       hva_change = true;
+               }
        }
 
        gpc->uhva += page_offset;
@@ -319,7 +332,10 @@ out_unlock:
 
 int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len)
 {
-       return __kvm_gpc_refresh(gpc, gpc->gpa, len);
+       if (gpc->gpa != KVM_XEN_INVALID_GPA)
+               return __kvm_gpc_refresh(gpc, gpc->gpa, true, len);
+
+       return __kvm_gpc_refresh(gpc, gpc->uhva, false, len);
 }
 
 void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm)
@@ -332,7 +348,8 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm)
        gpc->uhva = KVM_HVA_ERR_BAD;
 }
 
-int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
+static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, u64 addr, bool addr_is_gpa,
+                             unsigned long len)
 {
        struct kvm *kvm = gpc->kvm;
 
@@ -353,7 +370,17 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
                gpc->active = true;
                write_unlock_irq(&gpc->lock);
        }
-       return __kvm_gpc_refresh(gpc, gpa, len);
+       return __kvm_gpc_refresh(gpc, addr, addr_is_gpa, len);
+}
+
+int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
+{
+       return __kvm_gpc_activate(gpc, gpa, true, len);
+}
+
+int kvm_gpc_activate_hva(struct gfn_to_pfn_cache *gpc, unsigned long hva, unsigned long len)
+{
+       return __kvm_gpc_activate(gpc, hva, false, len);
 }
 
 void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)