Re: [PATCH] memory: synchronize dirty bitmap before unmapping a range

Jan Kiszka
2011-08-01T07:52:26Z

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On 2011-08-01 09:34, Jan Kiszka wrote:
> On 2011-07-31 21:47, Avi Kivity wrote:
>> When a range is being unmapped, ask accelerators (e.g. kvm) to synchronize the
>> dirty bitmap to avoid losing information forever.
>>
>> Fixes grub2 screen update.
>
> I does.
>
> But something is still broken. As I reported before, the performance of
> grub2 startup is an order of magnitude slower than with the existing
> code. According to ftrace, we are getting tons of additional
> EPT_MISCONFIG exits over the 0xA0000 segment. But I haven't spot the
> difference yet. The effective slot setup as communicated to kvm looks
> innocent.

I take it back: We obviously once in a while resume the guest with the
vga segment unmapped. And that, of course, ends up doing mmio instead of
plain ram accesses.

Jan

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