[Xen-ia64-devel] RE: vcpu_translate issue

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

The warning is there because the current code doesn't yet
work properly for a region 0 virtual address.  Even
if you remove the printf, I don't think ltp mmap09 will
work properly because the current code assumes
incorrectly that every region 0 access is a guest
physical access.  Bug!  I think this is the first time
we have seen a region 0 virtual address.

Also, the printf is very good at catching problems when
there is a new bug in Xen so it would be nice to
keep the printf.  Perhaps it could be tied to a
Xen command line option: warnregion0.  E.g.

if (metaphysical) {
        if (address >> 61)
                panic_domain(("bad metaphysical address")
        else {
                ... existing phys translate code
        }
{
else if (!(address >> 61) && warnregion0) {
        printf
}

I think this code will also fix region 0 virtual addresses
(because it properly falls through to the rest of
vcpu_translate).

> -----Original Message-----
> From: Xu, Anthony [mailto:anthony.xu@xxxxxxxxx] 
> Sent: Friday, November 04, 2005 3:20 AM
> To: Magenheimer, Dan (HP Labs Fort Collins)
> Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Subject: vcpu_translate issue
> 
> Dan,
> 
> In vcpu_translate function, if guest address is within region 
> 0 and guest is in virtual mode, vcpu_translate will print 
> warning message and don't translate. It seems you assume 
> guest will not access this kind of address, but actually 
> guest application can allocate region 0 address spaces by 
> using system call mmap.
> 
> You can try testcase mmap09 of ltp on both native and xen0 to 
> find out this.
> 
> So, Can we remove this code segment in vcpu_translate?
> 
> Thanks,
> Anthony.
> 
> 

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