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

Some pfncache 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>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
---
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
v11:
 - Fixed kvm_gpc_check() to ignore memslot generation if the cache is not
   activated with a GPA. (This breakage occured during the re-work for v8).

v9:
 - Pass both GPA and HVA into __kvm_gpc_refresh() rather than overloading
   the address paraneter and using a bool flag to indicated what it is.

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 6097f076a7b0810c18816ba19baf0050089d7b05..8120674b87b091bf52cf09693072d8458960994d 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1345,6 +1345,22 @@ 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.
  *
@@ -1399,7 +1415,9 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
 static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
 {
        lockdep_assert_held(&gpc->lock);
-       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 97eec8ee34493a9c0dd6df702a8a35c97b094db7..ae822bff812fed7aee71ae881a4545df4c725ecf 100644 (file)
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -48,7 +48,10 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)
        if (!gpc->active)
                return false;
 
-       if (gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva))
+       if (gpc->gpa != KVM_XEN_INVALID_GPA && gpc->generation != slots->generation)
+               return false;
+
+       if (kvm_is_error_hva(gpc->uhva))
                return false;
 
        if (offset_in_page(gpc->uhva) + len > PAGE_SIZE)
@@ -209,11 +212,13 @@ 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, gpa_t gpa, unsigned long uhva,
                             unsigned long len)
 {
        struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
-       unsigned long page_offset = offset_in_page(gpa);
+       unsigned long page_offset = (gpa != KVM_XEN_INVALID_GPA) ?
+               offset_in_page(gpa) :
+               offset_in_page(uhva);
        bool unmap_old = false;
        unsigned long old_uhva;
        kvm_pfn_t old_pfn;
@@ -246,9 +251,15 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
        old_khva = (void *)PAGE_ALIGN_DOWN((uintptr_t)gpc->khva);
        old_uhva = PAGE_ALIGN_DOWN(gpc->uhva);
 
-       /* Refresh the userspace HVA if necessary */
-       if (gpc->gpa != gpa || gpc->generation != slots->generation ||
-           kvm_is_error_hva(gpc->uhva)) {
+       if (gpa == KVM_XEN_INVALID_GPA) {
+               gpc->gpa = KVM_XEN_INVALID_GPA;
+               gpc->uhva = PAGE_ALIGN_DOWN(uhva);
+
+               if (gpc->uhva != old_uhva)
+                       hva_change = true;
+       } else if (gpc->gpa != gpa ||
+                  gpc->generation != slots->generation ||
+                  kvm_is_error_hva(gpc->uhva)) {
                gfn_t gfn = gpa_to_gfn(gpa);
 
                gpc->gpa = gpa;
@@ -319,7 +330,7 @@ out_unlock:
 
 int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len)
 {
-       return __kvm_gpc_refresh(gpc, gpc->gpa, len);
+       return __kvm_gpc_refresh(gpc, gpc->gpa, gpc->uhva, len);
 }
 
 void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm)
@@ -332,7 +343,8 @@ 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, gpa_t gpa, unsigned long uhva,
+                             unsigned long len)
 {
        struct kvm *kvm = gpc->kvm;
 
@@ -353,7 +365,17 @@ 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, gpa, uhva, len);
+}
+
+int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
+{
+       return __kvm_gpc_activate(gpc, gpa, KVM_HVA_ERR_BAD, len);
+}
+
+int kvm_gpc_activate_hva(struct gfn_to_pfn_cache *gpc, unsigned long uhva, unsigned long len)
+{
+       return __kvm_gpc_activate(gpc, KVM_XEN_INVALID_GPA, uhva, len);
 }
 
 void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)