From: Paul Durrant <pdurrant@amazon.com>
Date: Fri, 10 Nov 2023 10:32:21 +0000 (+0000)
Subject: consistently use khva for offset in existing cache
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=594e70842281af7a289d883cb702e1c7317d450b;p=people%2Fpauldu%2Flinux.git

consistently use khva for offset in existing cache

keep offset in uhva and use that when remapping

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 0eeb034d0674..610ff72fb631 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -48,15 +48,15 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)
 	if (!gpc->active)
 		return false;
 
-	if (offset_in_page(gpc->gpa) + len > PAGE_SIZE)
-		return false;
-
 	if (gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva))
 		return false;
 
 	if (!gpc->valid)
 		return false;
 
+	if (offset_in_page(gpc->khva) + len > PAGE_SIZE)
+		return false;
+
 	return true;
 }
 
@@ -118,8 +118,9 @@ static inline bool mmu_notifier_retry_cache(struct kvm *kvm, unsigned long mmu_s
 
 static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 {
-	/* Note, the new page offset may be different than the old! */
-	void *old_khva = gpc->khva - offset_in_page(gpc->khva);
+	unsigned long old_page_offset = offset_in_page(gpc->khva);
+	unsigned long page_offset = offset_in_page(gpc->uhva);
+	void *old_khva = gpc->khva - old_page_offset;
 	kvm_pfn_t new_pfn = KVM_PFN_ERR_FAULT;
 	void *new_khva = NULL;
 	unsigned long mmu_seq;
@@ -192,7 +193,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 
 	gpc->valid = true;
 	gpc->pfn = new_pfn;
-	gpc->khva = new_khva + offset_in_page(gpc->gpa);
+	gpc->khva = new_khva + page_offset;
 
 	/*
 	 * Put the reference to the _new_ pfn.  The pfn is now tracked by the
@@ -215,8 +216,9 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
 	unsigned long page_offset = offset_in_page(gpa);
 	bool unmap_old = false;
-	unsigned long old_uhva;
+	unsigned long old_page_offset;
 	kvm_pfn_t old_pfn;
+	bool hva_change = false;
 	void *old_khva;
 	int ret;
 
@@ -242,8 +244,8 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 	}
 
 	old_pfn = gpc->pfn;
-	old_khva = gpc->khva - offset_in_page(gpc->khva);
-	old_uhva = gpc->uhva;
+	old_page_offset = offset_in_page(gpc->khva);
+	old_khva = gpc->khva - old_page_offset;
 
 	/* If the userspace HVA is invalid, refresh that first */
 	if (gpc->gpa != gpa || gpc->generation != slots->generation ||
@@ -259,13 +261,24 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 			ret = -EFAULT;
 			goto out;
 		}
+
+		hva_change = true;
+	} else {
+		/*
+		 * No need to do any re-mapping if the only thing that has
+		 * changed is the page offset. Just subtract the old offset
+		 * before the new one is added in.
+		 */
+		gpc->uhva -= old_page_offset;
 	}
 
+	gpc->uhva += page_offset;
+
 	/*
 	 * If the userspace HVA changed or the PFN was already invalid,
 	 * drop the lock and do the HVA to PFN lookup again.
 	 */
-	if (!gpc->valid || old_uhva != gpc->uhva) {
+	if (!gpc->valid || hva_change) {
 		ret = hva_to_pfn_retry(gpc);
 	} else {
 		/*