[PATCH v13 46/85] KVM: guest_memfd: Provide "struct page" as output from kvm_gmem_get_pfn()

Sean Christopherson
2024-10-10T18:26:29Z

Provide the "struct page" associated with a guest_memfd pfn as an output
from __kvm_gmem_get_pfn() so that KVM guest page fault handlers can
directly put the page instead of having to rely on
kvm_pfn_to_refcounted_page().

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/mmu/mmu.c | 2 +-
arch/x86/kvm/svm/sev.c | 10 ++++++----
include/linux/kvm_host.h | 6 ++++--
virt/kvm/guest_memfd.c | 8 ++++++--
4 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 2e2076287aaf..a038cde74f0d 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4400,7 +4400,7 @@ static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu,
}

r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn,
- &max_order);
+ &fault->refcounted_page, &max_order);
if (r) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return r;
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 4557ff3804ae..c6c852485900 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3849,6 +3849,7 @@ static int __sev_snp_update_protected_guest_state(struct kvm_vcpu *vcpu)
if (VALID_PAGE(svm->sev_es.snp_vmsa_gpa)) {
gfn_t gfn = gpa_to_gfn(svm->sev_es.snp_vmsa_gpa);
struct kvm_memory_slot *slot;
+ struct page *page;
kvm_pfn_t pfn;

slot = gfn_to_memslot(vcpu->kvm, gfn);
@@ -3859,7 +3860,7 @@ static int __sev_snp_update_protected_guest_state(struct kvm_vcpu *vcpu)
* The new VMSA will be private memory guest memory, so
* retrieve the PFN from the gmem backend.
*/
- if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, NULL))
+ if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, &page, NULL))
return -EINVAL;

/*
@@ -3888,7 +3889,7 @@ static int __sev_snp_update_protected_guest_state(struct kvm_vcpu *vcpu)
* changes then care should be taken to ensure
* svm->sev_es.vmsa is pinned through some other means.
*/
- kvm_release_pfn_clean(pfn);
+ kvm_release_page_clean(page);
}

/*
@@ -4688,6 +4689,7 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
struct kvm_memory_slot *slot;
struct kvm *kvm = vcpu->kvm;
int order, rmp_level, ret;
+ struct page *page;
bool assigned;
kvm_pfn_t pfn;
gfn_t gfn;
@@ -4714,7 +4716,7 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
return;
}

- ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, &order);
+ ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, &page, &order);
if (ret) {
pr_warn_ratelimited("SEV: Unexpected RMP fault, no backing page for private GPA 0x%llx\n",
gpa);
@@ -4772,7 +4774,7 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
out:
trace_kvm_rmp_fault(vcpu, gpa, pfn, error_code, rmp_level, ret);
out_no_trace:
- put_page(pfn_to_page(pfn));
+ kvm_release_page_unused(page);
}

static bool is_pfn_range_shared(kvm_pfn_t start, kvm_pfn_t end)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3b9afb40e935..504483d35197 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2490,11 +2490,13 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)

#ifdef CONFIG_KVM_PRIVATE_MEM
int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
- gfn_t gfn, kvm_pfn_t *pfn, int *max_order);
+ gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
+ int *max_order);
#else
static inline int kvm_gmem_get_pfn(struct kvm *kvm,
struct kvm_memory_slot *slot, gfn_t gfn,
- kvm_pfn_t *pfn, int *max_order)
+ kvm_pfn_t *pfn, struct page **page,
+ int *max_order)
{
KVM_BUG_ON(1, kvm);
return -EIO;
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 8a878e57c5d4..47a9f68f7b24 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -594,7 +594,8 @@ static struct folio *__kvm_gmem_get_pfn(struct file *file,
}

int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
- gfn_t gfn, kvm_pfn_t *pfn, int *max_order)
+ gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
+ int *max_order)
{
pgoff_t index = kvm_gmem_get_index(slot, gfn);
struct file *file = kvm_gmem_get_file(slot);
@@ -615,7 +616,10 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio);

folio_unlock(folio);
- if (r < 0)
+
+ if (!r)
+ *page = folio_file_page(folio, index);
+ else
folio_put(folio);

out:
--
2.47.0.rc1.288.g06298d1525-goog