linux-kernel - [PATCH 1/8] KVM: pfncache: add a map helper function

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Date:   Thu, 14 Sep 2023 08:49:39 +0000
From:   Paul Durrant <paul@....org>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Paul Durrant <pdurrant@...zon.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: [PATCH 1/8] KVM: pfncache: add a map helper function

From: Paul Durrant <pdurrant@...zon.com>

We have an unmap helper but mapping is open-coded. Arguably this is fine
because mapping is done in only one place, hva_to_pfn_retry(), but adding
the helper does make that function more readable.

Signed-off-by: Paul Durrant <pdurrant@...zon.com>
---
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: David Woodhouse <dwmw2@...radead.org>
---
 virt/kvm/pfncache.c | 43 +++++++++++++++++++++++++------------------
 1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 2d6aba677830..0f36acdf577f 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -96,17 +96,28 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_check);
 
-static void gpc_unmap_khva(kvm_pfn_t pfn, void *khva)
+static void *gpc_map(kvm_pfn_t pfn)
+{
+	if (pfn_valid(pfn))
+		return kmap(pfn_to_page(pfn));
+#ifdef CONFIG_HAS_IOMEM
+	else
+		return memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB);
+#endif
+}
+
+static void gpc_unmap(kvm_pfn_t pfn, void *khva)
 {
 	/* Unmap the old pfn/page if it was mapped before. */
-	if (!is_error_noslot_pfn(pfn) && khva) {
-		if (pfn_valid(pfn))
-			kunmap(pfn_to_page(pfn));
+	if (is_error_noslot_pfn(pfn) || !khva)
+		return;
+
+	if (pfn_valid(pfn))
+		kunmap(pfn_to_page(pfn));
 #ifdef CONFIG_HAS_IOMEM
-		else
-			memunmap(khva);
+	else
+		memunmap(khva);
 #endif
-	}
 }
 
 static inline bool mmu_notifier_retry_cache(struct kvm *kvm, unsigned long mmu_seq)
@@ -175,7 +186,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 			 * the existing mapping and didn't create a new one.
 			 */
 			if (new_khva != old_khva)
-				gpc_unmap_khva(new_pfn, new_khva);
+				gpc_unmap(new_pfn, new_khva);
 
 			kvm_release_pfn_clean(new_pfn);
 
@@ -193,15 +204,11 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 		 * too must be done outside of gpc->lock!
 		 */
 		if (gpc->usage & KVM_HOST_USES_PFN) {
-			if (new_pfn == gpc->pfn) {
+			if (new_pfn == gpc->pfn)
 				new_khva = old_khva;
-			} else if (pfn_valid(new_pfn)) {
-				new_khva = kmap(pfn_to_page(new_pfn));
-#ifdef CONFIG_HAS_IOMEM
-			} else {
-				new_khva = memremap(pfn_to_hpa(new_pfn), PAGE_SIZE, MEMREMAP_WB);
-#endif
-			}
+			else
+				new_khva = gpc_map(new_pfn);
+
 			if (!new_khva) {
 				kvm_release_pfn_clean(new_pfn);
 				goto out_error;
@@ -326,7 +333,7 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 	mutex_unlock(&gpc->refresh_lock);
 
 	if (unmap_old)
-		gpc_unmap_khva(old_pfn, old_khva);
+		gpc_unmap(old_pfn, old_khva);
 
 	return ret;
 }
@@ -412,7 +419,7 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)
 		list_del(&gpc->list);
 		spin_unlock(&kvm->gpc_lock);
 
-		gpc_unmap_khva(old_pfn, old_khva);
+		gpc_unmap(old_pfn, old_khva);
 	}
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_deactivate);
-- 
2.39.2