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Re: [Qemu-arm] [RFC v4 4/5] hw/arm/virt: Add 2.10 machine type
From: |
Auger Eric |
Subject: |
Re: [Qemu-arm] [RFC v4 4/5] hw/arm/virt: Add 2.10 machine type |
Date: |
Wed, 31 May 2017 09:15:12 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
Hi Peter,
On 30/05/2017 18:04, Peter Maydell wrote:
> On 13 May 2017 at 18:43, Eric Auger <address@hidden> wrote:
>> The new machine type allows smmuv3 instantiation. A new option
>> is introduced to turn the feature on/off (off by default).
>
> Should we go for default-on, or would that break guests?
> For other things added to the virt board I think the
> approach we've taken has been:
> * if this is just an extra device, simply provide it in the
> new virt-n.nn machine by default
> * if this is something that changes how the machine behaves
> even for code that doesn't care about that feature (eg
> EL2, EL3, since they change what mode you start in on boot)
> then default it to off
> * if the feature only works with TCG and not KVM then
> maybe default it to off
OK thanks for the guidelines. I put it off by default since it can
largely degrade the performance in some use cases. Also instantiating
the smmu can also induce some option changes at other levels: for
instance virtio-pci devices may be used along with iommu_platform option
for the guest to use dma ops.
Thanks
Eric
>
> thanks
> -- PMM
>
- [Qemu-arm] [RFC v4 0/5] ARM SMMUv3 Emulation Support, Eric Auger, 2017/05/13
- [Qemu-arm] [RFC v4 1/5] hw/arm/smmu-common: smmu base class, Eric Auger, 2017/05/13
- [Qemu-arm] [RFC v4 3/5] hw/arm/virt: Add SMMUv3 to the virt board, Eric Auger, 2017/05/13
- [Qemu-arm] [RFC v4 4/5] hw/arm/virt: Add 2.10 machine type, Eric Auger, 2017/05/13
- [Qemu-arm] [RFC v4 2/5] hw/arm/smmuv3: smmuv3 emulation model, Eric Auger, 2017/05/13
- [Qemu-arm] [RFC v4 5/5] hw/arm/virt-acpi-build: add smmuv3 node in IORT table, Eric Auger, 2017/05/13
- Re: [Qemu-arm] [RFC v4 0/5] ARM SMMUv3 Emulation Support, Peter Maydell, 2017/05/30