linux-kernel - [RFC PATCH 3/5] mm: userfaultfd: allow to register userfaultfd for guest

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Message-ID: <20250303133011.44095-4-kalyazin@amazon.com>
Date: Mon, 3 Mar 2025 13:30:09 +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 3/5] mm: userfaultfd: allow to register userfaultfd for guest_memfd

Signed-off-by: Nikita Kalyazin <kalyazin@...zon.com>
---
 include/linux/userfaultfd_k.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 75342022d144..440d38903359 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -20,6 +20,10 @@
 #include <asm-generic/pgtable_uffd.h>
 #include <linux/hugetlb_inline.h>
 
+#ifdef CONFIG_KVM_PRIVATE_MEM
+bool kvm_gmem_vma_is_gmem(struct vm_area_struct *vma);
+#endif
+
 /* The set of all possible UFFD-related VM flags. */
 #define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR)
 
@@ -242,6 +246,11 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma,
 		return false;
 #endif
 
+#ifdef CONFIG_KVM_PRIVATE_MEM
+	if (kvm_gmem_vma_is_gmem(vma))
+		return true;
+#endif
+
 	/* By default, allow any of anon|shmem|hugetlb */
 	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
 	    vma_is_shmem(vma);
-- 
2.47.1