Re: [Xen-devel] [PATCH][RFC]Move PCI Configuration Spacesfrom Dom0 to Xen

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

I think we can safely follow qemu here and return all-1s on reads when the
enable bit in cf8 is clear. I'll make that change.

 -- Keir

On 11/4/08 01:42, "Shan, Haitao" <haitao.shan@xxxxxxxxx> wrote:

> Actually I do not find a clear explanation in MCH specification on this.
> Luckily, dom0's kernel does not write 0xcf8 without valid bit set.
> Does access to 0xCFC return data based on the last valid latched data in
> 0xCF8, or last latched data without valid bit set in 0xCF8?
> For example:
> Outl(0x80000000, 0xcf8);
> Outl(0x00000001, 0xcf8);
> Inl(0xcfc); <----This is skipped? Or data at 00:00.0 register 0.
> Another question is:
> Outl(0x80000000, 0xcf8);
> Inb(0xcfc);
> Inb(0xcfd); <----This is skipped? Or data at 00:00.0 register 1?
> Can you tell me where do you find these answers? Thanks!
> 
> Shan Haitao
> 
> -----Original Message-----
> From: Espen Skoglund [mailto:espen.skoglund@xxxxxxxxxxxxx]
> Sent: 2008年4月11日 0:55
> To: Haitao Shan
> Cc: Keir Fraser; Shan, Haitao; Tian, Kevin; xen-devel; Kay, Allen M; Jiang,
> Yunhong; Han, Weidong
> Subject: Re: [Xen-devel] [PATCH][RFC]Move PCI Configuration Spacesfrom Dom0 to
> Xen
> 
> I believe dword writes to 0xCF8 should always be latched into the
> internal shadow register, irrespective of whether the enable bit (bit
> 31) is set.  Accesseses to 0xCFC can then safely be skipped if enable
> bit in latch register is not set.
> 
> eSk
> 
> 
> 
> [Haitao Shan]
>> Thanks, Keir!
>> 2008/4/10, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>:
>>> 
>>> On 10/4/08 10:45, "Shan, Haitao" <haitao.shan@xxxxxxxxx> wrote:
>>> 
>>> This patch will move reading and writing of PCI configuration
>>> spaces from dom0 to Xen. It also changes VTD code, so that they can
>>> touch the PCI configuration spaces with proper lock.
>>> 
>>> This will also benefit MSI support in Xen.
>>> Can you give some comments? Thanks!
>>> 
>>> 
>>> The approach is fine. I will read it more thoroughly, clean it up a bit if
>>> necessary, and certainly check it in.
>>> 
>>> -- Keir
>>> 
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-devel
>>> 
>>> 
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