On 2011-10-18 17:22, Jan Kiszka wrote: > What KVM has to do is just mapping an arbitrary MSI message > (theoretically 64+32 bits, in practice it's much of course much less) to
( There are 24 distinguishing bits in an MSI message on x86, but that's only a current interpretation of one specific arch. ) > a single GSI and vice versa. As there are less GSIs than possible MSI > messages, we could run out of them when creating routes, statically or > lazily. > > What would probably help us long-term out of your concerns regarding > lazy routing is to bypass that redundant GSI translation for dynamic > messages, i.e. those that are not associated with an irqfd number or an > assigned device irq. Something like a KVM_DELIVER_MSI IOCTL that accepts > address and data directly. This would be a trivial extension in fact. Given its beneficial impact on our GSI limitation issue, I think I will hack up something like that. And maybe this makes a transparent cache more reasonable. Then only old host kernels would force us to do searches for already cached messages. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
