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Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests |
Date: |
Mon, 13 May 2019 11:46:29 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 |
On 5/12/19 1:36 AM, Andrew Jones wrote:
> CPU type | accel | sve-max-vq | sve-vls-map
> -------------------------------------------
> 1) max | tcg | $MAX_VQ | $VLS_MAP
> 2) max | kvm | $MAX_VQ | $VLS_MAP
> 3) host | kvm | N/A | $VLS_MAP
This doesn't seem right. Why is -cpu host not whatever the host supports? It
certainly has been so far. I really don't see how -cpu max makes any sense for
kvm.
> The QMP query returns a list of valid vq lists. For example, if
> a guest can use vqs 1, 2, 3, and 4, then the following list will
> be returned
>
> [ [ 1 ], [ 1, 2 ], [ 1, 2, 3 ], [ 1, 2, 3, 4 ] ]
>
> Another example might be 1, 2, 4, as the architecture states 3
> is optional. In that case the list would be
>
> [ [ 1 ], [ 1, 2 ], [ 1, 2, 4 ] ]
>
> This may look redundant, but it's necessary to provide a future-
> proof query, because while KVM currently requires vector sets to
> be strict truncations of the full valid vector set, that may change
> at some point.
How and why would that make sense?
Real hardware is going to support one set of vector lengths. Whether VQ=3 is
valid or not is not going to depend on the maximum VQ, surely.
I'll also note that if we want to support the theoretical
beyond-current-architecture maximum VQ=512, such that migration works
seemlessly with current hardware, then we're going to have to change the
migration format.
So far I'm supporting only the current architecture maximum VQ=16. Which
seemed plenty, given that the first round of hardware only supports VQ=4.
r~
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, (continued)
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Andrew Jones, 2019/05/14
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Andrea Bolognani, 2019/05/14
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Richard Henderson, 2019/05/14
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Andrea Bolognani, 2019/05/15
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Dave Martin, 2019/05/15
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Andrea Bolognani, 2019/05/15
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Dave Martin, 2019/05/15
- Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Andrew Jones, 2019/05/15
Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests, Peter Maydell, 2019/05/13
Re: [Qemu-devel] [PATCH 00/13] target/arm/kvm: enable SVE in guests,
Richard Henderson <=