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Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED
From: |
Christoffer Dall |
Subject: |
Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED |
Date: |
Thu, 14 May 2015 14:24:13 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, May 14, 2015 at 02:08:49PM +0200, Paolo Bonzini wrote:
>
>
> On 14/05/2015 14:00, Christoffer Dall wrote:
> > So, getting back to my original question. Is the point then that UEFI
> > must assume (from ACPI/DT) the cache-coherency properties of the PCI
> > controller which exists in hardware on the system you're running on,
> > even for the virtual PCI bus because that will be the semantics for
> > assigned devices?
> >
> > And in that case, we have no way to distinguish between passthrough
> > devices and virtual devices plugged into the virtual PCI bus?
>
> Well, we could use the subsystem id. But it's a hack, and may cause
> incompatibilities with some drivers. Michael, any ideas?
>
> > What about the idea of having two virtual PCI buses on your system where
> > one is always cache-coherent and uses for virtual devices, and the other
> > is whatever the hardware is and used for passthrough devices?
>
> I think that was rejected before.
>
Do you remember where? I just remember Catalin mentioning the idea to
me verbally.
Besides the slightly heavy added use of resources etc. it seems like it
would address some of our issues in a good way.
But I'm still not sure why UEFI/Linux currently sees our PCI bus as
being non-coherent when in fact it is and we have no passthrough issues
currently. Are all PCI controllers always non-coherent for some reason
and therefore we model it as such too?
-Christoffer
- Re: [Qemu-devel] [RFC/RFT PATCH v2 2/3] KVM: promote KVM_MEMSLOT_INCOHERENT to uapi, (continued)
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Christoffer Dall, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Laszlo Ersek, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Christoffer Dall, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Paolo Bonzini, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Christoffer Dall, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Paolo Bonzini, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Christoffer Dall, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Paolo Bonzini, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED,
Christoffer Dall <=
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Paolo Bonzini, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Christoffer Dall, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Laszlo Ersek, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Peter Maydell, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Andrew Jones, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Laszlo Ersek, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Michael S. Tsirkin, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Laszlo Ersek, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Michael S. Tsirkin, 2015/05/14
- Re: [Qemu-devel] [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED, Ard Biesheuvel, 2015/05/15