[PATCH v8 4/8] KVM: x86/mmu: Migrate to __kvm_follow_pfn

[David Stevens]

From: David Stevens <stevensd at chromium.org>

Migrate from __gfn_to_pfn_memslot to __kvm_follow_pfn. Most arguments
directly map to the new API. The largest change is replacing the async
in/out parameter with FOLL_NOWAIT parameter and the KVM_PFN_ERR_NEEDS_IO
return value.

Signed-off-by: David Stevens <stevensd at chromium.org>
---
 arch/x86/kvm/mmu/mmu.c | 41 +++++++++++++++++++++++++++++++----------
 1 file changed, 31 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index ec169f5c7dce..dabae67f198b 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),
+		.try_map_writable = true,
+	};
 
 	/*
 	 * Retry the page fault if the gfn hit a memslot that is being deleted
@@ -4325,12 +4330,20 @@ 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))
+		goto success;
+
+	/*
+	 * If __kvm_follow_pfn() failed because I/O is needed to fault in the
+	 * page, then either set up an asynchronous #PF to do the I/O, or if
+	 * doing an async #PF isn't possible, retry __kvm_follow_pfn() with
+	 * I/O allowed. All other failures are fatal, i.e. retrying won't help.
+	 */
+	if (fault->pfn != KVM_PFN_ERR_NEEDS_IO)
+		return RET_PF_CONTINUE;
 
 	if (!fault->prefetch && kvm_can_do_async_pf(vcpu)) {
 		trace_kvm_try_async_get_page(fault->addr, fault->gfn);
@@ -4348,9 +4361,17 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 	 * to wait for IO.  Note, gup always bails if it is unable to quickly
 	 * get a page and a fatal signal, i.e. SIGKILL, is pending.
 	 */
-	fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, true, NULL,
-					  fault->write, &fault->map_writable,
-					  &fault->hva);
+	foll.flags |= FOLL_INTERRUPTIBLE;
+	foll.flags &= ~FOLL_NOWAIT;
+	fault->pfn = __kvm_follow_pfn(&foll);
+
+	if (!is_error_noslot_pfn(fault->pfn))
+		goto success;
+
+	return RET_PF_CONTINUE;
+success:
+	fault->hva = foll.hva;
+	fault->map_writable = foll.writable;
 	return RET_PF_CONTINUE;
 }
 
-- 
2.42.0.rc1.204.g551eb34607-goog