From: Jason Gunthorpe <jgg@nvidia.com>
To: Ankit Agrawal <ankita@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>,
"maz@kernel.org" <maz@kernel.org>,
"oliver.upton@linux.dev" <oliver.upton@linux.dev>,
"joey.gouly@arm.com" <joey.gouly@arm.com>,
"suzuki.poulose@arm.com" <suzuki.poulose@arm.com>,
"yuzenghui@huawei.com" <yuzenghui@huawei.com>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
"will@kernel.org" <will@kernel.org>,
"ryan.roberts@arm.com" <ryan.roberts@arm.com>,
"shahuang@redhat.com" <shahuang@redhat.com>,
"lpieralisi@kernel.org" <lpieralisi@kernel.org>,
"ddutile@redhat.com" <ddutile@redhat.com>,
"seanjc@google.com" <seanjc@google.com>,
Aniket Agashe <aniketa@nvidia.com>, Neo Jia <cjia@nvidia.com>,
Kirti Wankhede <kwankhede@nvidia.com>,
Krishnakant Jaju <kjaju@nvidia.com>,
"Tarun Gupta (SW-GPU)" <targupta@nvidia.com>,
Vikram Sethi <vsethi@nvidia.com>,
Andy Currid <acurrid@nvidia.com>,
Alistair Popple <apopple@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
Dan Williams <danw@nvidia.com>, Zhi Wang <zhiw@nvidia.com>,
Matt Ochs <mochs@nvidia.com>, Uday Dhoke <udhoke@nvidia.com>,
Dheeraj Nigam <dnigam@nvidia.com>,
"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
"sebastianene@google.com" <sebastianene@google.com>,
"coltonlewis@google.com" <coltonlewis@google.com>,
"kevin.tian@intel.com" <kevin.tian@intel.com>,
"yi.l.liu@intel.com" <yi.l.liu@intel.com>,
"ardb@kernel.org" <ardb@kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"gshan@redhat.com" <gshan@redhat.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"tabba@google.com" <tabba@google.com>,
"qperret@google.com" <qperret@google.com>,
"kvmarm@lists.linux.dev" <kvmarm@lists.linux.dev>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"maobibo@loongson.cn" <maobibo@loongson.cn>
Subject: Re: [PATCH v9 6/6] KVM: arm64: Expose new KVM cap for cacheable PFNMAP
Date: Fri, 4 Jul 2025 13:56:18 -0300 [thread overview]
Message-ID: <20250704165618.GP1410929@nvidia.com> (raw)
In-Reply-To: <SA1PR12MB7199AB9F09DF483AEC41777AB042A@SA1PR12MB7199.namprd12.prod.outlook.com>
On Fri, Jul 04, 2025 at 04:20:07PM +0000, Ankit Agrawal wrote:
> Thanks Jason and David for reviewing the patch!
>
> >> >
> >> > I don't know if any VMM will ever use this, but it looks OK
> >>
> >> So, should we defer it to the point where we actually have a use case?
> >>
> >> I mean, patch #4 could be simplified by modifying arm64 code in patch #5
> >> only. No need for a common kvm_arch function etc.
> >
> > IDK, I think Marc and Oliver are right it makes sense to have it, I
> > just don't really see how a VMM would make use of it..
> >
> > Jason
>
> Right, it was also pointed out that the VMM could make use of it
> for early termination during VM migration between incompatible
> systems (i.e. across systems with and without FWB and CACHE DIC).
In practice it isn't that useful.
This is all linked to VFIO so the receiving VMM and system must
already have VFIO load and must already have the VMM told to use the
coherent VFIO mapping.
It would be a serious misconfiguration to setup a VMM as a migration
target when the configuration can't even boot normally - because
memslot creation would fail for the VFIO coherent memory.
Regardless, in such a case the memslot creation should fail and the
migration will abort.
Jason
next prev parent reply other threads:[~2025-07-04 16:56 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-21 4:21 [PATCH v9 0/6] KVM: arm64: Map GPU device memory as cacheable ankita
2025-06-21 4:21 ` [PATCH v9 1/6] KVM: arm64: Rename the device variable to s2_force_noncacheable ankita
2025-07-04 13:41 ` Jason Gunthorpe
2025-07-04 13:57 ` David Hildenbrand
2025-06-21 4:21 ` [PATCH v9 2/6] KVM: arm64: Update the check to detect device memory ankita
2025-07-04 13:43 ` Jason Gunthorpe
2025-07-04 14:02 ` David Hildenbrand
2025-06-21 4:21 ` [PATCH v9 3/6] KVM: arm64: Block cacheable PFNMAP mapping ankita
2025-06-27 13:49 ` Will Deacon
2025-06-30 1:56 ` Ankit Agrawal
2025-06-30 12:25 ` Jason Gunthorpe
2025-07-04 12:21 ` David Hildenbrand
2025-07-04 16:04 ` Will Deacon
2025-07-04 16:47 ` Jason Gunthorpe
2025-07-08 12:47 ` Will Deacon
2025-07-04 13:45 ` Jason Gunthorpe
2025-07-04 14:09 ` David Hildenbrand
2025-06-21 4:21 ` [PATCH v9 4/6] KVM: arm64: New function to determine hardware cache management support ankita
2025-07-04 13:47 ` Jason Gunthorpe
2025-07-04 14:10 ` David Hildenbrand
2025-06-21 4:21 ` [PATCH v9 5/6] KVM: arm64: Allow cacheable stage 2 mapping using VMA flags ankita
2025-07-04 14:04 ` Jason Gunthorpe
2025-07-04 14:13 ` David Hildenbrand
2025-07-04 16:51 ` Ankit Agrawal
2025-06-21 4:21 ` [PATCH v9 6/6] KVM: arm64: Expose new KVM cap for cacheable PFNMAP ankita
2025-07-04 13:44 ` Jason Gunthorpe
2025-07-04 14:15 ` David Hildenbrand
2025-07-04 15:04 ` Jason Gunthorpe
2025-07-04 16:20 ` Ankit Agrawal
2025-07-04 16:56 ` Jason Gunthorpe [this message]
2025-06-27 5:03 ` [PATCH v9 0/6] KVM: arm64: Map GPU device memory as cacheable Ankit Agrawal
2025-07-02 9:33 ` Ankit Agrawal
2025-07-02 16:51 ` Donald Dutile
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20250704165618.GP1410929@nvidia.com \
--to=jgg@nvidia.com \
--cc=acurrid@nvidia.com \
--cc=akpm@linux-foundation.org \
--cc=alex.williamson@redhat.com \
--cc=aniketa@nvidia.com \
--cc=ankita@nvidia.com \
--cc=apopple@nvidia.com \
--cc=ardb@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=cjia@nvidia.com \
--cc=coltonlewis@google.com \
--cc=danw@nvidia.com \
--cc=david@redhat.com \
--cc=ddutile@redhat.com \
--cc=dnigam@nvidia.com \
--cc=gshan@redhat.com \
--cc=jhubbard@nvidia.com \
--cc=joey.gouly@arm.com \
--cc=kevin.tian@intel.com \
--cc=kjaju@nvidia.com \
--cc=kvmarm@lists.linux.dev \
--cc=kwankhede@nvidia.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lpieralisi@kernel.org \
--cc=maobibo@loongson.cn \
--cc=maz@kernel.org \
--cc=mochs@nvidia.com \
--cc=oliver.upton@linux.dev \
--cc=qperret@google.com \
--cc=ryan.roberts@arm.com \
--cc=seanjc@google.com \
--cc=sebastianene@google.com \
--cc=shahuang@redhat.com \
--cc=suzuki.poulose@arm.com \
--cc=tabba@google.com \
--cc=targupta@nvidia.com \
--cc=udhoke@nvidia.com \
--cc=vsethi@nvidia.com \
--cc=will@kernel.org \
--cc=yi.l.liu@intel.com \
--cc=yuzenghui@huawei.com \
--cc=zhiw@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox