KVM: SEV: Use long-term pin when registering encrypted memory regions

JIRA: https://issues.redhat.com/browse/RHEL-95318

commit 7e066cb
Author: Ge Yang <yangge1116@126.com>
Date:   Tue Feb 11 10:37:03 2025 +0800

    KVM: SEV: Use long-term pin when registering encrypted memory regions

    When registering an encrypted memory region for SEV-MEM/SEV-ES guests,
    pin the pages with FOLL_TERM so that the pages are migrated out of
    MIGRATE_CMA/ZONE_MOVABLE.  Failure to do so violates the CMA/MOVABLE
    mechanisms and can result in fragmentation due to unmovable pages, e.g.
    can make CMA allocations fail.

    Signed-off-by: Ge Yang <yangge1116@126.com>
    Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
    Acked-by: David Hildenbrand <david@redhat.com>
    Link: https://lore.kernel.org/r/1739241423-14326-1-git-send-email-yangge1116@126.com
    [sean: massage changelog, make @flags an unsigned int]
    Signed-off-by: Sean Christopherson <seanjc@google.com>

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: Maxim Levitsky

arch/x86/kvm/svm/sev.c

@@ -627,7 +627,7 @@ static int sev_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
 
 static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 				    unsigned long ulen, unsigned long *n,
-				    int write)
+				    unsigned int flags)
 {
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
 	unsigned long npages, size;
@@ -668,7 +668,7 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 		return ERR_PTR(-ENOMEM);
 
 	/* Pin the user virtual address. */
-	npinned = pin_user_pages_fast(uaddr, npages, write ? FOLL_WRITE : 0, pages);
+	npinned = pin_user_pages_fast(uaddr, npages, flags, pages);
 	if (npinned != npages) {
 		pr_err("SEV: Failure locking %lu pages.\n", npages);
 		ret = -ENOMEM;
@@ -756,7 +756,7 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	vaddr_end = vaddr + size;
 
 	/* Lock the user memory. */
-	inpages = sev_pin_memory(kvm, vaddr, size, &npages, 1);
+	inpages = sev_pin_memory(kvm, vaddr, size, &npages, FOLL_WRITE);
 	if (IS_ERR(inpages))
 		return PTR_ERR(inpages);
 
@@ -1255,7 +1255,7 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
 		if (IS_ERR(src_p))
 			return PTR_ERR(src_p);
 
-		dst_p = sev_pin_memory(kvm, dst_vaddr & PAGE_MASK, PAGE_SIZE, &n, 1);
+		dst_p = sev_pin_memory(kvm, dst_vaddr & PAGE_MASK, PAGE_SIZE, &n, FOLL_WRITE);
 		if (IS_ERR(dst_p)) {
 			sev_unpin_memory(kvm, src_p, n);
 			return PTR_ERR(dst_p);
@@ -1321,7 +1321,7 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
 		return -EFAULT;
 
-	pages = sev_pin_memory(kvm, params.guest_uaddr, params.guest_len, &n, 1);
+	pages = sev_pin_memory(kvm, params.guest_uaddr, params.guest_len, &n, FOLL_WRITE);
 	if (IS_ERR(pages))
 		return PTR_ERR(pages);
 
@@ -1803,7 +1803,7 @@ static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 
 	/* Pin guest memory */
 	guest_page = sev_pin_memory(kvm, params.guest_uaddr & PAGE_MASK,
-				    PAGE_SIZE, &n, 1);
+				    PAGE_SIZE, &n, FOLL_WRITE);
 	if (IS_ERR(guest_page)) {
 		ret = PTR_ERR(guest_page);
 		goto e_free_trans;
@@ -2705,7 +2705,8 @@ int sev_mem_enc_register_region(struct kvm *kvm,
 		return -ENOMEM;
 
 	mutex_lock(&kvm->lock);
-	region->pages = sev_pin_memory(kvm, range->addr, range->size, &region->npages, 1);
+	region->pages = sev_pin_memory(kvm, range->addr, range->size, &region->npages,
+				       FOLL_WRITE | FOLL_LONGTERM);
 	if (IS_ERR(region->pages)) {
 		ret = PTR_ERR(region->pages);
 		mutex_unlock(&kvm->lock);