Introduce helper functions to map and unmap guest memory into host kernel
memory. These helper functions support mapping guest memory both that are
managed by the host kernel (i.e. have a "struct page") and the ones that
are not managed by the kernel (i.e. does not have a "struct page").
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
---
include/linux/kvm_host.h | 18 ++++++++++++++
virt/kvm/kvm_main.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 80 insertions(+)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6bdd4b9..45d2854 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -204,6 +204,12 @@ enum {
READING_SHADOW_PAGE_TABLES,
};
+struct kvm_host_mapping {
+ struct page *page;
+ void *kaddr;
+ kvm_pfn_t pfn;
+};
+
/*
* Sometimes a large or cross-page mmio needs to be broken up into separate
* exits for userspace servicing.
@@ -700,6 +706,10 @@ struct kvm_memslots *kvm_vcpu_memslots(struct kvm_vcpu *vcpu);
struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn);
kvm_pfn_t kvm_vcpu_gfn_to_pfn_atomic(struct kvm_vcpu *vcpu, gfn_t gfn);
kvm_pfn_t kvm_vcpu_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn);
+bool kvm_vcpu_gfn_to_host_mapping(struct kvm_vcpu *vcpu, gfn_t gfn,
+ struct kvm_host_mapping *mapping,
+ bool kernel_access);
+void kvm_release_host_mapping(struct kvm_host_mapping *mapping, bool dirty);
struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn);
unsigned long kvm_vcpu_gfn_to_hva(struct kvm_vcpu *vcpu, gfn_t gfn);
unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *writable);
@@ -990,6 +1000,14 @@ static inline hpa_t pfn_to_hpa(kvm_pfn_t pfn)
return (hpa_t)pfn << PAGE_SHIFT;
}
+static inline bool kvm_vcpu_gpa_to_host_mapping(struct kvm_vcpu *vcpu, gpa_t gpa,
+ struct kvm_host_mapping *mapping,
+ bool kernel_access)
+{
+ return kvm_vcpu_gfn_to_host_mapping(vcpu, gpa_to_gfn(gpa), mapping,
+ kernel_access);
+}
+
static inline struct page *kvm_vcpu_gpa_to_page(struct kvm_vcpu *vcpu,
gpa_t gpa)
{
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 210bf82..2b9f93d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1653,6 +1653,68 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
}
EXPORT_SYMBOL_GPL(gfn_to_page);
+bool kvm_vcpu_gfn_to_host_mapping(struct kvm_vcpu *vcpu, gfn_t gfn,
+ struct kvm_host_mapping *mapping,
+ bool kernel_access)
+{
+ void *kaddr = NULL;
+ kvm_pfn_t pfn;
+ struct page *page = NULL;
+
+ pfn = kvm_vcpu_gfn_to_pfn(vcpu, gfn);
+
+ if (pfn_valid(pfn)) {
+ page = kvm_pfn_to_page(pfn);
+ if (is_error_page(page))
+ return false;
+
+ if (kernel_access) {
+ kaddr = kmap(page);
+ if (!kaddr)
+ return false;
+ }
+
+ mapping->kaddr = kaddr;
+ mapping->page = page;
+ mapping->pfn = pfn;
+ return true;
+ }
+
+ kaddr = memremap(pfn << PAGE_SHIFT, PAGE_SIZE, MEMREMAP_WB);
+ if (!kaddr)
+ return false;
+
+ mapping->page = NULL;
+ mapping->kaddr = kaddr;
+ mapping->pfn = pfn;
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_kaddr);
+
+void kvm_release_host_mapping(struct kvm_host_mapping *mapping, bool dirty)
+{
+ if (mapping->page) {
+ if (mapping->kaddr)
+ kunmap(mapping->page);
+
+ if (dirty)
+ kvm_release_page_dirty(mapping->page);
+ else
+ kvm_release_page_clean(mapping->page);
+ } else {
+ if (mapping->kaddr)
+ memunmap(mapping->kaddr);
+
+ if (dirty)
+ kvm_release_pfn_dirty(mapping->pfn);
+ else
+ kvm_release_pfn_clean(mapping->pfn);
+ }
+
+ memset(mapping, 0, sizeof(*mapping));
+}
+
struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn)
{
kvm_pfn_t pfn;
--
2.7.4
