On Wed, Feb 04, 2015 at 04:53:54PM +0100, Igor Mammedov wrote: > > > > Isn't this will cause a VMEXIT when the guest is reading the GUID? If it > > > > is then this idea was already presented and Michael didn't approve it. > > > It will, but is it performance critical? VM supposed to read it > > > at start-up and on getting notification. So I think VMEXIT in this case > > > is not sufficient to drop simple and strait-forward design. > > > > I agree with you on that and one of the previous patches did used a > > fixed-address to store the GUID while read/write access were handled by > > qemu driver code. But as I wrote before, it was Michael who didn't approved > > it so I proposed this method although it is a bit more complicated. > > > > I don't know how to break out of this dead-lock... :( > Could you post a link to driver based version of series. > Perhaps we could address Michael's comments and still stay > with a simple implementation.
The point is to keep all allocations in guest. I don't want to "steal" a page from guest. > > > > > > > > BTW: > > > For start-up fw_cfg file is not any way better, it's also causes VMEXIT > > > for every byte it reads from it. > > > > I don't understand your claim. Accessing the fw_cfg "file" doesn't cause > > VMEXIT as it located somewhere in the guest's memory range. > As far as I'm aware MMIO or ioport is used for reading fw_cfg contents > on guest side, one byte at a time and every such access causes VMEXIT > into QEMU callback. It's highly unlikely to be measureable. Prove me wrong if you like. -- MST
