Re: kvm-27 vs 28 I/O speed

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Luca wrote:
> On 7/13/07, Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
>> Dave Hansen wrote:
>> > On Thu, 2007-07-12 at 08:37 +0300, Avi Kivity wrote:
>> >
>> >> Can you confirm it by backing out that one patch?
>> >>
>> >
>> > Do you know the git commit id by chance?
>> >
>> > -- Dave
>> >
>> >
>> commit 55a3212bc2f5ecddcd4c5cdf2bfb37ad71e45ff2
>> Author: Luca Tettamanti <kronos.it-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> Date:   Tue Jun 5 14:47:33 2007 +0300
>>
>>     kvm: qemu: initialize ata ports as enabled
>>
>>     this allows libata to see the qemu ata ports.
>>
>> diff --git a/qemu/hw/ide.c b/qemu/hw/ide.c
>> index 190f074..ddfb9bc 100644
>> --- a/qemu/hw/ide.c
>> +++ b/qemu/hw/ide.c
>> @@ -2586,6 +2586,8 @@ static void piix3_reset(PCIIDEState *d)
>>      pci_conf[0x06] = 0x80; /* FBC */
>>      pci_conf[0x07] = 0x02; // PCI_status_devsel_medium
>>      pci_conf[0x20] = 0x01; /* BMIBA: 20-23h */
>> +    pci_conf[0x41] = 0x80; // enable port 0
>> +    pci_conf[0x43] = 0x80; // enable port 1
>>  }
>>
>>  void pci_piix_ide_init(PCIBus *bus, BlockDriverState **hd_table, int
>> devfn)
>>
>>
>> I was unable to reproduce this on a FC6 i386 guest.
>
> Hum... I assume the FC6 is using the "old" IDE driver, yes? I can't
> see why that patch should matter though... if those bits are not set
> then the IDE controller is not decoding the commands (on real hw).
>

I tested FC6 i386 about found no difference with or without the patch.

Dave, can you diff the guest dmesg with kvm-27 and kvm-28 userspace? 
Maybe that will tell us something.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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