RE: [PATCH] KVM: Qemu: Flush i-cache after ide-dma operation in IA64

["Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>]

Avi Kivity wrote:
> Avi Kivity wrote:
>>>> 
>>> 
>>> It doesn't had to do it.  The PCI transaction will automatically
>>> invalidate caches - but qemu doesn't emulate this (and doesn't need
>>> to do on x86). 
>>> 
>> 
>> So any DMA on ia64 will flush the instruction caches?!
>> 
> 
> Or maybe, the host kernel will do it after the transaction completes?

Host kernel doesn't do anything about cache flush after DMA, since it thinks platform guarantees that. 

> In our case the lack of zero-copy means the host is invalidating the
> wrong addresses (memcpy source) and leaving the real destination
> intact. 

We just need to sync the target address(destination address), because only its physical address belongs to guest, and likely to be the DMA target address of guest. 

Xiantao
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