[PATCH v13 30/85] KVM: Migrate kvm_vcpu_map() to kvm_follow_pfn()

[Sean Christopherson]

From: David Stevens <steve...@chromium.org>

Migrate kvm_vcpu_map() to kvm_follow_pfn(), and have it track whether or
not the map holds a refcounted struct page.  Precisely tracking struct
page references will eventually allow removing kvm_pfn_to_refcounted_page()
and its various wrappers.

Signed-off-by: David Stevens <steve...@chromium.org>
[sean: use a pointer instead of a boolean]
Tested-by: Alex Bennée <alex.ben...@linaro.org>
Signed-off-by: Sean Christopherson <sea...@google.com>
---
 include/linux/kvm_host.h |  2 +-
 virt/kvm/kvm_main.c      | 26 ++++++++++++++++----------
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e3c01cbbc41a..02ab3a657aa6 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -280,6 +280,7 @@ struct kvm_host_map {
         * can be used as guest memory but they are not managed by host
         * kernel).
         */
+       struct page *refcounted_page;
        struct page *page;
        void *hva;
        kvm_pfn_t pfn;
@@ -1238,7 +1239,6 @@ void kvm_release_pfn_dirty(kvm_pfn_t pfn);
 void kvm_set_pfn_dirty(kvm_pfn_t pfn);
 void kvm_set_pfn_accessed(kvm_pfn_t pfn);
 
-void kvm_release_pfn(kvm_pfn_t pfn, bool dirty);
 int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
                        int len);
 int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6cdbd0516d58..b1c1b7e4f33a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3093,21 +3093,21 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_page);
 
-void kvm_release_pfn(kvm_pfn_t pfn, bool dirty)
-{
-       if (dirty)
-               kvm_release_pfn_dirty(pfn);
-       else
-               kvm_release_pfn_clean(pfn);
-}
-
 int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
 {
+       struct kvm_follow_pfn kfp = {
+               .slot = gfn_to_memslot(vcpu->kvm, gfn),
+               .gfn = gfn,
+               .flags = FOLL_WRITE,
+               .refcounted_page = &map->refcounted_page,
+       };
+
+       map->refcounted_page = NULL;
        map->page = NULL;
        map->hva = NULL;
        map->gfn = gfn;
 
-       map->pfn = gfn_to_pfn(vcpu->kvm, gfn);
+       map->pfn = kvm_follow_pfn(&kfp);
        if (is_error_noslot_pfn(map->pfn))
                return -EINVAL;
 
@@ -3139,10 +3139,16 @@ void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct 
kvm_host_map *map, bool dirty)
        if (dirty)
                kvm_vcpu_mark_page_dirty(vcpu, map->gfn);
 
-       kvm_release_pfn(map->pfn, dirty);
+       if (map->refcounted_page) {
+               if (dirty)
+                       kvm_release_page_dirty(map->refcounted_page);
+               else
+                       kvm_release_page_clean(map->refcounted_page);
+       }
 
        map->hva = NULL;
        map->page = NULL;
+       map->refcounted_page = NULL;
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_unmap);
 
-- 
2.47.0.rc1.288.g06298d1525-goog