From: Avi Kivity <avi@redhat.com>
To: Cam Macdonell <cam@cs.ualberta.ca>
Cc: KVM General <kvm@vger.kernel.org>
Subject: Re: ioeventfd usage in KVM
Date: Fri, 12 Mar 2010 18:43:38 +0200 [thread overview]
Message-ID: <4B9A6F3A.8080507@redhat.com> (raw)
In-Reply-To: <8286e4ee1003120750g5aad52a2se6a9bd0796984c7c@mail.gmail.com>
On 03/12/2010 05:50 PM, Cam Macdonell wrote:
>
>> Yes - they must match. Not PIO is faster on x86 but nonexistant elsewhere.
>>
>
s/Not/Note/.
> Does it matter that PIO is slower since with ioeventfd Qemu is being
> bypassed all together?
mmio is slower in kvm, not qemu; mmio must go through the emulator,
fetch the instruction, decode and execute it, while pio decoding is done
by the processor microcode.
> Can I use the memory space with ioeventfds?
>
Yes.
> There doesn't seem to be a flag (KVM_IOEVENTFD_FLAG_MMIO) for it.
>
If you don't specify _PIO, _MMIO is the default, as
Documentation/kvm/api.txt doesn't say.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
prev parent reply other threads:[~2010-03-12 16:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-12 5:08 ioeventfd usage in KVM Cam Macdonell
2010-03-12 7:43 ` Avi Kivity
2010-03-12 15:50 ` Cam Macdonell
2010-03-12 16:43 ` Avi Kivity [this message]
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