linux-kernel - [PATCH 4/4] KVM: document KVM_GUEST_MEMFD

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Message-ID: <20241024095429.54052-5-kalyazin@amazon.com>
Date: Thu, 24 Oct 2024 09:54:29 +0000
From: Nikita Kalyazin <kalyazin@...zon.com>
To: <pbonzini@...hat.com>, <corbet@....net>, <kvm@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <jthoughton@...gle.com>, <brijesh.singh@....com>, <michael.roth@....com>,
	<graf@...zon.de>, <jgowans@...zon.com>, <roypat@...zon.co.uk>,
	<derekmn@...zon.com>, <nsaenz@...zon.es>, <xmarcalx@...zon.com>,
	<kalyazin@...zon.com>
Subject: [PATCH 4/4] KVM: document KVM_GUEST_MEMFD_POPULATE ioctl

Signed-off-by: Nikita Kalyazin <kalyazin@...zon.com>
---
 Documentation/virt/kvm/api.rst | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index e32471977d0a..f192dab41bad 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6442,6 +6442,30 @@ the capability to be present.
 
 `flags` must currently be zero.
 
+4.144 KVM_GUEST_MEMFD_POPULATE
+----------------------------
+
+:Capability: KVM_CAP_GUEST_MEMFD
+:Architectures: none
+:Type: vm ioctl
+:Parameters: struct kvm_guest_memfd_populate(in)
+:Returns: 0 if all requested pages populated, < 0 on error
+
+KVM_GUEST_MEMFD_POPULATE populates guest_memfd with data provided by userspace.
+
+::
+
+  struct kvm_guest_memfd_populate {
+  __u64 gpa;
+  __u64 size;
+  void __user *from;
+  __u64 flags;
+  };
+
+A gfn can only be populated once.  If a gfn is attempted to get populated
+multiple times without prior calls to fallocate(PUNCH_HOLE), subsequent calls
+will return EEXIST.
+If the `from` pointer is NULL, the pages are cleared.
 
 5. The kvm_run structure
 ========================
-- 
2.40.1