On 2015-04-21 13:32, Paolo Bonzini wrote:
> Basically it's an optimization.  The guest can set the UC memory type on
> PCI BARs that are actually backed by RAM in QEMU, and then accesses to
> these BARs will be unnecessarily slow.  It would be particularly bad if,
> for example, access to ivshmem were slowed down because the guest PAT
> says the memory is uncacheable.

ivshmem is pv anyway - why shouldn't the guest driver take this room for
optimization into account and ask for a cached mapping?

Is that that only use case?

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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