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[Qemu-devel] Re: sparc solaris guest, hsfs_putpage: dirty HSFS page

From: Blue Swirl
Subject: [Qemu-devel] Re: sparc solaris guest, hsfs_putpage: dirty HSFS page
Date: Tue, 26 Jan 2010 21:23:04 +0200

On Tue, Jan 26, 2010 at 7:03 PM, Artyom Tarasenko
<address@hidden> wrote:
> 2010/1/24 Blue Swirl <address@hidden>:
>> On Sun, Jan 24, 2010 at 2:02 AM, Artyom Tarasenko
>> <address@hidden> wrote:
>>> All solaris versions which currently boot (from cd) regularly produce 
>>> buckets of
>>> "hsfs_putpage: dirty HSFS page" messages.
>>> High Sierra is a pretty old and stable stuff, so it is possible that
>>> the code is similar to OpenSolaris.
>>> I looked in debugger, and the function calls hierarchy looks pretty similar.
>>> Now in the OpenSolaris source code there is a nice comment:
>>> http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/hsfs/hsfs_vnops.c#1758
>>> /*
>>> * Normally pvn_getdirty() should return 0, which
>>> * impies that it has done the job for us.
>>> * The shouldn't-happen scenario is when it returns 1.
>>> * This means that the page has been modified and
>>> * needs to be put back.
>>> * Since we can't write on a CD, we fake a failed
>>> * I/O and force pvn_write_done() to destroy the page.
>>> */
>>> if (pvn_getdirty(pp, flags) == 1) {
>>>                cmn_err(CE_NOTE,
>>>                            "hsfs_putpage: dirty HSFS page");
>>> Now the question: does the problem have to do with qemu caches 
>>> (non-)emulation?
>>> Can it be that we mark non-dirty pages dirty? Or does qemu always mark
>>> pages dirty exactly to avoid cache emulation?
>>> Otherwise it means something else goes astray and Solaris guest really
>>> modifies the pages it shouldn't.
>>> Just wonder what to dig first, MMU or IRQ emulation (the two most
>>> obvious suspects).
>> Maybe the stores via MMU bypass ASIs
> why bypass stores? What about the non-bypass ones?

Because their use should update the PTE dirty bits.

>> should use
>> st[bwlq]_phys_notdirty.
> Seems that st[bw]_phys_notdirty are not implemeted yet?
> I've changed [lq] for asi 0x20 and 21-2f and see no difference. Also I
> put some debug printfs and see that none of these ASIs is called after
> the Solaris kernel is loaded.
>> It can break display handling, though.
> --
> Regards,
> Artyom Tarasenko
> solaris/sparc under qemu blog: http://tyom.blogspot.com/

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