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

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Message-ID: <20250901143000.5017-1-roypat@amazon.co.uk>
Date: Mon, 1 Sep 2025 14:30:01 +0000
From: "Roy, Patrick" <roypat@...zon.co.uk>
To: "david@...hat.com" <david@...hat.com>
CC: "ackerleytng@...gle.com" <ackerleytng@...gle.com>, "Manwaring, Derek"
	<derekmn@...zon.com>, "Thomson, Jack" <jackabt@...zon.co.uk>, "Kalyazin,
 Nikita" <kalyazin@...zon.co.uk>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "Roy, Patrick"
	<roypat@...zon.co.uk>, "rppt@...nel.org" <rppt@...nel.org>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "tabba@...gle.com"
	<tabba@...gle.com>, "vbabka@...e.cz" <vbabka@...e.cz>, "will@...nel.org"
	<will@...nel.org>, "Cali, Marco" <xmarcalx@...zon.co.uk>
Subject: Re: [PATCH v5 05/12] KVM: Documentation: describe
 GUEST_MEMFD_FLAG_NO_DIRECT_MAP

On Thu, 2025-08-28 at 11:27 +0100, David Hildenbrand wrote:
> On 28.08.25 11:39, Roy, Patrick wrote:
>> 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
> 
> WARNING: Missing commit description - Add an appropriate one

Admittedly wasn't sure what to say that wouldn't just repeat the commit title
or the contents. Maybe that just means this shouldn't be its own patch. Will
squash in the previous one (same for PATCH 11/12).

> WARNING: From:/Signed-off-by: email name mismatch: 'From: "Roy, Patrick"
> <roypat@...zon.co.uk>' != 'Signed-off-by: Patrick Roy <roypat@...zon.co.uk>'

Heh, my git config only ever uses "Patrick Roy <roypat@...zon.co.uk>". Not sure
where "Roy, Patrick" comes from, could it be the mail server mangling things?

> -- 
> Cheers
> 
> David / dhildenb
> 
Best,
Patrick