KVM: Drop KVM_ERR_PTR_BAD_PAGE and instead return NULL to indicate an error

Remove KVM_ERR_PTR_BAD_PAGE and instead return NULL, as "bad page" is just
a leftover bit of weirdness from days of old when KVM stuffed a "bad" page
into the guest instead of actually handling missing pages.  See commit
cea7bb21280e ("KVM: MMU: Make gfn_to_page() always safe").

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-2-seanjc@google.com>

6 files changed, 10 insertions, 20 deletions

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 7b8ae509328f..d7721297b9b6 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -645,7 +645,7 @@ static void kvmppc_patch_dcbz(struct kvm_vcpu *vcpu, struct kvmppc_pte *pte)
 	int i;
 
 	hpage = gfn_to_page(vcpu->kvm, pte->raddr >> PAGE_SHIFT);
-	if (is_error_page(hpage))
+	if (!hpage)
 		return;
 
 	hpage_offset = pte->raddr & ~PAGE_MASK;
diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
index 6e2ebbd8aaac..d9bf1bc3ff61 100644
--- a/arch/powerpc/kvm/book3s_xive_native.c
+++ b/arch/powerpc/kvm/book3s_xive_native.c
@@ -654,7 +654,7 @@ static int kvmppc_xive_native_set_queue_config(struct kvmppc_xive *xive,
 	}
 
 	page = gfn_to_page(kvm, gfn);
-	if (is_error_page(page)) {
+	if (!page) {
 		srcu_read_unlock(&kvm->srcu, srcu_idx);
 		pr_err("Couldn't get queue page %llx!\n", kvm_eq.qaddr);
 		return -EINVAL;
diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 89cafea4c41f..763a070f5955 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -661,7 +661,7 @@ static int pin_guest_page(struct kvm *kvm, gpa_t gpa, hpa_t *hpa)
 	struct page *page;
 
 	page = gfn_to_page(kvm, gpa_to_gfn(gpa));
-	if (is_error_page(page))
+	if (!page)
 		return -EINVAL;
 	*hpa = (hpa_t)page_to_phys(page) + (gpa & ~PAGE_MASK);
 	return 0;
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 2098dc689088..20526e4d6c62 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2664,7 +2664,7 @@ int kvm_alloc_apic_access_page(struct kvm *kvm)
 	}
 
 	page = gfn_to_page(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
-	if (is_error_page(page)) {
+	if (!page) {
 		ret = -EFAULT;
 		goto out;
 	}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 45be36e5285f..0b280e5bad0a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -153,13 +153,6 @@ static inline bool kvm_is_error_gpa(gpa_t gpa)
 	return gpa == INVALID_GPA;
 }
 
-#define KVM_ERR_PTR_BAD_PAGE	(ERR_PTR(-ENOENT))
-
-static inline bool is_error_page(struct page *page)
-{
-	return IS_ERR(page);
-}
-
 #define KVM_REQUEST_MASK           GENMASK(7,0)
 #define KVM_REQUEST_NO_WAKEUP      BIT(8)
 #define KVM_REQUEST_WAIT           BIT(9)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 141db5b79cd4..5fc95504affe 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3066,19 +3066,14 @@ EXPORT_SYMBOL_GPL(gfn_to_page_many_atomic);
  */
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 {
-	struct page *page;
 	kvm_pfn_t pfn;
 
 	pfn = gfn_to_pfn(kvm, gfn);
 
 	if (is_error_noslot_pfn(pfn))
-		return KVM_ERR_PTR_BAD_PAGE;
-
-	page = kvm_pfn_to_refcounted_page(pfn);
-	if (!page)
-		return KVM_ERR_PTR_BAD_PAGE;
+		return NULL;
 
-	return page;
+	return kvm_pfn_to_refcounted_page(pfn);
 }
 EXPORT_SYMBOL_GPL(gfn_to_page);
 
@@ -3172,7 +3167,8 @@ static void kvm_set_page_accessed(struct page *page)
 
 void kvm_release_page_clean(struct page *page)
 {
-	WARN_ON(is_error_page(page));
+	if (WARN_ON(!page))
+		return;
 
 	kvm_set_page_accessed(page);
 	put_page(page);
@@ -3196,7 +3192,8 @@ EXPORT_SYMBOL_GPL(kvm_release_pfn_clean);
 
 void kvm_release_page_dirty(struct page *page)
 {
-	WARN_ON(is_error_page(page));
+	if (WARN_ON(!page))
+		return;
 
 	kvm_set_page_dirty(page);
 	kvm_release_page_clean(page);