On 2012-02-14 08:12, Gerhard Wiesinger wrote: > Hello, > > Current QEMU-KVM VGA implementation have the following problem with > legacy OS (e.g. DOS with INT10h calls): Performance is low on accessing > A000:0 > page and doing bank switching at the 64k page. Do we already understand the mode and access patterns here? Which VGA adapter? Cirrus, standard, or any? What is the concrete test case (one that won't require me digging for MS Dose floppy disks in my basement)? > > Would a kernel mode VGA solve these problems? > How complicated is it? > Is it possible to have only some parts in kernel mode? > Any further ideas or suggestions? Provided we take heavy exits so far, in-kernel acceleration may reduce the exit overhead by factor, hmm, maybe 3-4. Better is to avoid exists completely, i.e. switch the region to RAM mode. But that depends on the graphic mode, and I'm afraid we have already covered all which can be mapped like this. In any case, before discussing solutions, we need to analyze the problem. Jan
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