linux-kernel - [RFC PATCH 2/5] KVM: guest_memfd: add support for uffd missing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250303133011.44095-3-kalyazin@amazon.com>
Date: Mon, 3 Mar 2025 13:30:08 +0000
From: Nikita Kalyazin <kalyazin@...zon.com>
To: <akpm@...ux-foundation.org>, <pbonzini@...hat.com>, <shuah@...nel.org>
CC: <kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<lorenzo.stoakes@...cle.com>, <david@...hat.com>, <ryan.roberts@....com>,
	<quic_eberman@...cinc.com>, <jthoughton@...gle.com>, <peterx@...hat.com>,
	<graf@...zon.de>, <jgowans@...zon.com>, <roypat@...zon.co.uk>,
	<derekmn@...zon.com>, <nsaenz@...zon.es>, <xmarcalx@...zon.com>,
	<kalyazin@...zon.com>
Subject: [RFC PATCH 2/5] KVM: guest_memfd: add support for uffd missing

Add support for sending a pagefault event if userfaultfd is registered.
Only page missing event is currently supported.

Signed-off-by: Nikita Kalyazin <kalyazin@...zon.com>
---
 virt/kvm/guest_memfd.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index af825f7494ea..358c3776ed66 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -4,6 +4,9 @@
 #include <linux/kvm_host.h>
 #include <linux/pagemap.h>
 #include <linux/anon_inodes.h>
+#ifdef CONFIG_KVM_PRIVATE_MEM
+#include <linux/userfaultfd_k.h>
+#endif /* CONFIG_KVM_PRIVATE_MEM */
 
 #include "kvm_mm.h"
 
@@ -332,9 +335,16 @@ static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf)
 	struct folio *folio;
 	vm_fault_t ret = VM_FAULT_LOCKED;
 
+	folio = filemap_get_entry(inode->i_mapping, vmf->pgoff);
+	if (!folio && userfaultfd_missing(vmf->vma))
+		return handle_userfault(vmf, VM_UFFD_MISSING);
+	if (folio)
+		folio_lock(folio);
+
 	filemap_invalidate_lock_shared(inode->i_mapping);
 
-	folio = kvm_gmem_get_folio(inode, vmf->pgoff);
+	if (!folio)
+		folio = kvm_gmem_get_folio(inode, vmf->pgoff);
 	if (IS_ERR(folio)) {
 		switch (PTR_ERR(folio)) {
 		case -EAGAIN:
-- 
2.47.1