On Thu, Jul 6, 2023 at 10:54 AM Isaku Yamahata [off-list ref] wrote:

On Tue, Jul 04, 2023 at 04:50:49PM +0900,
David Stevens [off-list ref] wrote:

quoted

From: David Stevens <redacted>

Migrate from __gfn_to_pfn_memslot to __kvm_follow_pfn.

Signed-off-by: David Stevens <redacted>
---
 arch/x86/kvm/mmu/mmu.c | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index ec169f5c7dce..e44ab512c3a1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c

@@ -4296,7 +4296,12 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
 static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 {
      struct kvm_memory_slot *slot = fault->slot;
-     bool async;
+     struct kvm_follow_pfn foll = {
+             .slot = slot,
+             .gfn = fault->gfn,
+             .flags = FOLL_GET | (fault->write ? FOLL_WRITE : 0),
+             .allow_write_mapping = true,
+     };

      /*
       * Retry the page fault if the gfn hit a memslot that is being deleted

@@ -4325,12 +4330,14 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
                      return RET_PF_EMULATE;
      }

-     async = false;
-     fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async,
-                                       fault->write, &fault->map_writable,
-                                       &fault->hva);
-     if (!async)
-             return RET_PF_CONTINUE; /* *pfn has correct page already */
+     foll.flags |= FOLL_NOWAIT;
+     fault->pfn = __kvm_follow_pfn(&foll);
+
+     if (!is_error_noslot_pfn(fault->pfn))

We have pfn in struct kvm_follow_pfn as output. Can we make __kvm_follow_pfn()
return int instead of kvm_pfn_t?  KVM_PFN_* seems widely used, though.

Switching __kvm_follow_pfn to return an int isn't difficult, but doing
is cleanly would require reworking the kvm_pfn_t/KVM_PFN_ERR_* api,
which as you said is quite widely used. That's a bit larger scope than
I want to do in this patch series.

-David