linux-kernel - [PATCH v5 05/12] KVM: Documentation: describe GUEST_MEMFD_FLAG_NO_DIRECT

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Message-ID: <20250828093902.2719-6-roypat@amazon.co.uk>
Date: Thu, 28 Aug 2025 09:39:22 +0000
From: "Roy, Patrick" <roypat@...zon.co.uk>
To: "david@...hat.com" <david@...hat.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>
CC: "Roy, Patrick" <roypat@...zon.co.uk>, "tabba@...gle.com"
	<tabba@...gle.com>, "ackerleytng@...gle.com" <ackerleytng@...gle.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "kvmarm@...ts.linux.dev"
	<kvmarm@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>,
	"rppt@...nel.org" <rppt@...nel.org>, "will@...nel.org" <will@...nel.org>,
	"vbabka@...e.cz" <vbabka@...e.cz>, "Cali, Marco" <xmarcalx@...zon.co.uk>,
	"Kalyazin, Nikita" <kalyazin@...zon.co.uk>, "Thomson, Jack"
	<jackabt@...zon.co.uk>, "Manwaring, Derek" <derekmn@...zon.com>
Subject: [PATCH v5 05/12] KVM: Documentation: describe
 GUEST_MEMFD_FLAG_NO_DIRECT_MAP

Signed-off-by: Patrick Roy <roypat@...zon.co.uk>
---
 Documentation/virt/kvm/api.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index c17a87a0a5ac..b52c14d58798 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6418,6 +6418,11 @@ When the capability KVM_CAP_GUEST_MEMFD_MMAP is supported, the 'flags' field
 supports GUEST_MEMFD_FLAG_MMAP.  Setting this flag on guest_memfd creation
 enables mmap() and faulting of guest_memfd memory to host userspace.
 
+When the capability KVM_CAP_GMEM_NO_DIRECT_MAP is supported, the 'flags' field
+supports GUEST_MEMFG_FLAG_NO_DIRECT_MAP. Setting this flag makes the guest_memfd
+instance behave similarly to memfd_secret, and unmaps the memory backing it from
+the kernel's address space after allocation.
+
 When the KVM MMU performs a PFN lookup to service a guest fault and the backing
 guest_memfd has the GUEST_MEMFD_FLAG_MMAP set, then the fault will always be
 consumed from guest_memfd, regardless of whether it is a shared or a private
-- 
2.50.1