Re: [Xen-ia64-devel] [PATCH]Fix the logic when deassign the mmio ranges for vti-domain.

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Tue, Mar 03, 2009 at 05:32:42PM +0800, Zhang, Xiantao wrote:
> 
> Isaku Yamahata wrote:
> > Could you elaborate on the concrete issue which you're seeing?
> > I guess the issue occurs when passed through pci device
> > is unplugged. But in that case, the region was occupied by
> > the device so that qemu haven't seen io on the area anyway.
> 
> For assigning a device to a hvm domain,  all mmio regions of the pci device 
> should be mapped in p2m table, but a corner case is that accessing some 
> pages(for example, vector table in msi-x's bar) in one region maybe need  
> route to qemu and emulate the corresponding logic in qemu.  In that case, we 
> have to remove the mapping for the specified pages in p2m, and let accessing 
> these pages intercepted by hyperviosr and forward the io requests to qemu.  
> But zap_domain_page_one can't intilziate the mmio p2m entries for hvm domain. 
>  Clear ?  :-)

You mean pt_iomem_map() which calls remove_msix_mapping() in
pass-through.c of qemu-dm? Is there any case other than msi-x?
I couldn't find any other usefull case because the current xen/ia64
doesn't support msi/msi-x.


> > And why GPFN_LOW_MMIO independently of addr? Shouldn't it be aware
> > of io_ranges[]?
> 
> For the low mmio ranges (3G-3.5G), we can use the fixed mfn GPFN_LOW_MMIO 
> combined with ASSIGN_io to indicate whether the p2m entries are mmio ranges.  
>  You may refer to io_ranges and it also use the fixed GPFN_LOW_MMIO to 
> intialize p2m entries for low mmio range. 

Hmm, there are two cases to call xc_domain_mempry_mapping(DPCI_REMOVE_MAPPING).
- Just to remove the entry.
  zap_domain_page_one() is wanted.

  the one in pt_iomem_map() and remove_msix_mapping() excpet called
  by pt_iomem_map()


- mmio on the area should be rounted to qemu-dm
  GPFN_LOW_MMIO and ASSIGN_io are wanted.

  remove_msix_mapping() which is called by pt_iomem_map().

Is there a way to distinguish them?

thanks,

> Xiantao
> 
> > 
> > On Tue, Mar 03, 2009 at 03:14:02PM +0800, Zhang, Xiantao wrote:
> >> PATCH: Fix the logic when deassign the mmio ranges for vti-domain.
> >> 
> >> When de-assign the mmio range, it should resume its original value
> >> for p2m value, otherwise, it may fail to determin mmio range's type.
> >> 
> >> Signed-off-by: Xiantao Zhang <xiantao.zhang@xxxxxxxxx>
> >> 
> >> diff -r 67f2e14613ef xen/arch/ia64/xen/mm.c
> >> --- a/xen/arch/ia64/xen/mm.c       Tue Feb 10 13:47:02 2009 +0800
> >> +++ b/xen/arch/ia64/xen/mm.c       Tue Mar 03 15:04:54 2009 +0800
> >> @@ -1508,8 +1508,14 @@ deassign_domain_mmio_page(struct domain      
> >>      return -EINVAL; }
> >> 
> >> -    for (; addr < end; addr += PAGE_SIZE )
> >> -        zap_domain_page_one(d, addr, 0, INVALID_MFN);
> >> +    for (; addr < end; addr += PAGE_SIZE ) {
> >> +  if (is_hvm_domain(d))
> >> +            __assign_domain_page(d, addr, GPFN_LOW_MMIO <<
> >> PAGE_SHIFT, +                                                 
> >> ASSIGN_writable |
> >> ASSIGN_io); +      else +            zap_domain_page_one(d, addr, 0,
> >> INVALID_MFN); +    } +
> >>      return 0;
> >>  }
> >> 
> > 
> >> _______________________________________________
> >> Xen-ia64-devel mailing list
> >> Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >> http://lists.xensource.com/xen-ia64-devel
> 
> 
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> 

-- 
yamahata

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