Re: [PATCH 2/7] qemu-kvm: Rename kvm_msix_message to KVMMsiMessage

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-04-27 16:40, Avi Kivity wrote:
> On 04/27/2011 05:30 PM, Jan Kiszka wrote:
>> On 2011-04-27 16:29, Avi Kivity wrote:
>>>  On 04/27/2011 05:04 PM, Jan Kiszka wrote:
>>>>>
>>>>>   I put kvm_msix_message in pci.h to avoid having every pci device pull in kvm.h
>>>>>   is anything wrong with that?  Maybe just rename it to make it generic
>>>>>   for msi and leave if where it is.
>>>>
>>>>  kvm.h shall provide kvm related types, not some unrelated header. That's
>>>>  even more important with MSI support for non-PCI devices (aka HPET).
>>>
>>>  We could have an MSIMessage type that abstracts the general facility,
>>>  and let it embed a KVMMsiMessage that contains just the gsi.
>>
>> Yes, likely also useful for generic MSI delivery services that bypass
>> stl_phys.
>>
> 
> Right, so you can cache the phys_page and apic lookups.
> 
> A different layer in which to accomplish this is to have a per-device 
> tlb.  So we'd have
> 
>      CachedPhysicalAddress msi_fsb_tlb;
> 
>      stl_phys_tlb(&msi_fsb_cache, addr, data);
> 
> which caches the addr lookup in a 1-entry tlb.  If we have many non-msi 
> repeated device writes to the same address, this might be worthwhile.  
>  From a quick look at the code, I don't think we do, though.

There is no caching need if the messages targets the fixed MSI address
window. We can simply pass it directly to the APIC then.

Jan

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