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Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested
From: |
Donald Dutile |
Subject: |
Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device |
Date: |
Wed, 27 Nov 2024 18:03:23 -0500 |
User-agent: |
Mozilla Thunderbird |
On 11/27/24 11:00 AM, Jason Gunthorpe wrote:
On Wed, Nov 27, 2024 at 10:21:24AM +0000, Shameerali Kolothum Thodi wrote:
For SMMUv3, NVIDIA-specific vCMDQ, it needs a parameter to state that
specifically,
since I'm concluding from reading the SMMUv3 version G.a spec, that
ECMDQ was added
to be able to assign an ECMDQ to a VM,
Not sure the intention of ECMDQ as per that specification is to assign
it to a VM. I think the main idea behind it is to have one Command Queue
per host CPU to eliminate lock contention while submitting commands
to SMMU.
Right
AFAIK it is not safe to assign one of the ECMDQ to guest yet. I think there is
no
way you can associate a VMID with ECMDQ. So there is no plan to
support ARM ECMDQ now.
Yep
'Yet' ...
The association would be done via the VMM -- no different then what associates
an assigned device to a VM today -- no hw-level (VM-)ID needed; a matter of
exposing
it to the VM, or not; or mapping the (virtual) CMDQ to the mapped/associated
ECMDQ.
They are purposedly mapped 64K apart from each other, enabling page-level
protection,
which I doubt is a per-CPU req for lock contention avoidance (large-cache-block
spaced would be sufficient, even 4k; it's 64k spaced btwn ECMDQ regs .. the
largest
ARM page size.
Summary: let's not assume this can't happen, and the chosen cmdline prevents it.
NVIDIA VCMDQ is a completely vendor specific one. Perhaps ARM may come
up with an assignable CMDQ in future though.
Yes, it is easy to imagine an ECMDQ extension that provides the same HW
features that VCMDQ has in future. I hope ARM will develop one.
Right, so how to know what op is being "accel"'d wrt smmuv3.
... and all needs to be per-instance ....
... libvirt (or any other VMM orchestrator) will need to determine
compatibility for
live migration. e.g., can one live migrate an accel=nv-vcmdq-based VM to
a host with
accel=ecmdq support? only nv-vcmdq? what if there are version diffs of
nv-vcmdq over time?
-- apologies, but I don't know the minute details of nv-vcmdq to
determine if that's unlikely or not.
Yes. This require more thought. But our first aim is get the basic smmuv3-accel
support.
Yeah, there is no live migration support yet in the SMMU qmeu driver,
AFAIK?
When it gets done the supported options will have to be considered
Jason
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, (continued)
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Nicolin Chen, 2024/11/13
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Donald Dutile, 2024/11/26
- RE: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Shameerali Kolothum Thodi, 2024/11/27
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Jason Gunthorpe, 2024/11/27
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Eric Auger, 2024/11/27
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Zhangfei Gao, 2024/11/27
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Eric Auger, 2024/11/28
- RE: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Shameerali Kolothum Thodi, 2024/11/28
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Eric Auger, 2024/11/28
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Jason Gunthorpe, 2024/11/28
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device,
Donald Dutile <=
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Jason Gunthorpe, 2024/11/28
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Donald Dutile, 2024/11/27
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Nicolin Chen, 2024/11/27
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Jason Gunthorpe, 2024/11/28
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Nicolin Chen, 2024/11/28
- RE: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Shameerali Kolothum Thodi, 2024/11/28
- RE: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Shameerali Kolothum Thodi, 2024/11/14
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Eric Auger, 2024/11/14
- RE: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Shameerali Kolothum Thodi, 2024/11/14
- Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device, Nicolin Chen, 2024/11/15