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

Sean Christopherson
2024-10-10T18:59:13Z

From: David Stevens <stevensd@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 <stevensd@chromium.org>
[sean: use a pointer instead of a boolean]
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@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);