linux-kernel - [PATCH] KVM: x86: report sev_pin_memory errors with PTR

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Message-Id: <20200623091725.271605-1-pbonzini@redhat.com>
Date:   Tue, 23 Jun 2020 05:17:25 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: [PATCH] KVM: x86: report sev_pin_memory errors with PTR_ERR

Callers of sev_pin_memory() treat
NULL differently:

sev_launch_secret()/svm_register_enc_region() return -ENOMEM
sev_dbg_crypt() returns -EFAULT.

Switching to ERR_PTR() preserves the error and enables cleaner reporting of
different kinds of failures.

Suggested-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm/sev.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index a893624b9275..2b4916ffa906 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -320,7 +320,7 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 	unsigned long first, last;
 
 	if (ulen == 0 || uaddr + ulen < uaddr)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	/* Calculate number of pages. */
 	first = (uaddr & PAGE_MASK) >> PAGE_SHIFT;
@@ -331,11 +331,11 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 	if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
 		pr_err("SEV: %lu locked pages exceed the lock limit of %lu.\n", locked, lock_limit);
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	if (WARN_ON_ONCE(npages > INT_MAX))
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	/* Avoid using vmalloc for smaller buffers. */
 	size = npages * sizeof(struct page *);
@@ -345,7 +345,7 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 		pages = kmalloc(size, GFP_KERNEL_ACCOUNT);
 
 	if (!pages)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	/* Pin the user virtual address. */
 	npinned = pin_user_pages_fast(uaddr, npages, write ? FOLL_WRITE : 0, pages);
@@ -360,11 +360,13 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 	return pages;
 
 err:
-	if (npinned > 0)
+	if (npinned > 0) {
 		unpin_user_pages(pages, npinned);
+		npinned = -ENOMEM;
+	}
 
 	kvfree(pages);
-	return NULL;
+	return ERR_PTR(npinned);
 }
 
 static void sev_unpin_memory(struct kvm *kvm, struct page **pages,
@@ -864,8 +866,8 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		return -EFAULT;
 
 	pages = sev_pin_memory(kvm, params.guest_uaddr, params.guest_len, &n, 1);
-	if (!pages)
-		return -ENOMEM;
+	if (IS_ERR(pages))
+		return PTR_ERR(pages);
 
 	/*
 	 * The secret must be copied into contiguous memory region, lets verify
@@ -991,8 +993,8 @@ int svm_register_enc_region(struct kvm *kvm,
 		return -ENOMEM;
 
 	region->pages = sev_pin_memory(kvm, range->addr, range->size, &region->npages, 1);
-	if (!region->pages) {
-		ret = -ENOMEM;
+	if (IS_ERR(region->pages)) {
+		ret = PTR_ERR(region->pages);
 		goto e_free;
 	}
 
-- 
2.26.2