kvm's vapic

[Jan Kiszka <jan.kiszka@web.de>]

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Hi all,

I'm studying the TPR access optimization in qemu-kvm for quite a while
now. It's one of the, well, let's call it "hardest" parts of qemu-kvm I
dealt with so far. But it's slowly getting clearer.

One thing I'm wondering now: This is practically targeting only 32-bit
Windows, right? Already the assumption that we find a CPU index at
fs:0x51 is apparently hard-coding this. Or that kernel code is at
0x8xxxxxxx or 0xExxxxxxx.

But what makes sure that we aren't patching some other obscure OS that
doesn't comply with our assumptions but triggers the TPR access reports
nevertheless? Is there a way to detect the supported target OSes
reliably before patching anything? Otherwise this feature has to remain
off by default in upstream, I suppose.

Jan


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