On Sun, Sep 5, 2010 at 10:50 AM, Avi Kivity
<address@hidden> wrote:
On 09/04/2010 01:22 AM, Cam Macdonell wrote:
Hi,
I'm trying to test 2 GB (and eventually larger) BARs with ivshmem and
I get an error in the guest that it is able to find a mem resource for
a BAR larger than 1GB. I'm using 64-bit BARs.
when running with 6GB of RAM and a 1GB BAR for ivshmem, it finds a
resource (and searches beyond 32-bit values to find it). Here is a
log from printfs added to the loop that searches the resources from
find_resource() in kernel/resource.c:363.
trying 'tmp.start' 1000 to
'tmp.end' fff
trying 'tmp.start' 9f400 to
'tmp.end' 9f3ff
trying 'tmp.start' a0000 to
'tmp.end' effff
trying 'tmp.start' 100000 to
'tmp.end' fffff
trying 'tmp.start' dfffd000 to
'tmp.end' dfffcfff
trying 'tmp.start' e0000000 to
'tmp.end' efffffff
trying 'tmp.start' f2000000 to
'tmp.end' f1ffffff
trying 'tmp.start' f2001000 to
'tmp.end' f200ffff
trying 'tmp.start' f2020000 to
'tmp.end' f201ffff
trying 'tmp.start' f2021000 to
'tmp.end' f202ffff
trying 'tmp.start' f2040000 to
'tmp.end' f203ffff
trying 'tmp.start' f2040100 to
'tmp.end' febfffff
trying 'tmp.start' fec00400 to
'tmp.end' fffbffff
trying 'tmp.start' 100000000 to
'tmp.end' ffffffff
trying 'tmp.start' 1a0000000 to
'tmp.end' ffffffffffffffff
pci 0000:00:04.0: BAR 2: assigned [mem 0x1c0000000-0x1ffffffff 64bit]
pci 0000:00:04.0: BAR 2: set to [mem 0x1c0000000-0x1ffffffff 64bit]
(PCI address [0x1c0000000-0x1ffffffff]
and you can see the BAR is successfully assigned.
However, with a 2GB BAR (below), the search fails, but it also never
searches beyong 32-bits. Again, all that's changed is the size of the
ivshmem region.
trying 'tmp.start' 1000 to
'tmp.end' fff
trying 'tmp.start' 9f400 to
'tmp.end' 9f3ff
trying 'tmp.start' a0000 to
'tmp.end' effff
trying 'tmp.start' 100000 to
'tmp.end' fffff
trying 'tmp.start' dfffd000 to
'tmp.end' dfffcfff
pci 0000:00:04.0: BAR 2: can't assign mem (size 0x80000000)
Is there a limit to PCI BAR sizes or resources? Any pointers or
further debugging tips are greatly appreciated.
latest kvm git, 2.6.36-rc2+
Please add printks to the loop so we can see this->start and this->end. It smells like a truncation issue.
Success with a 1GB BAR
this->start 1000, this->end 9f3ff
this->start 9f400, this->end 9ffff
this->start f0000, this->end fffff
this->start 100000, this->end dfffcfff
this->start dfffd000, this->end dfffffff
this->start f0000000, this->end f1ffffff
this->start f2000000, this->end f2000fff
this->start f2010000, this->end f201ffff
this->start f2020000, this->end f2020fff
this->start f2030000, this->end f203ffff
this->start f2040000, this->end f20400ff
this->start fec00000, this->end fec003ff
this->start fffc0000, this->end ffffffff
this->start 100000000, this->end 11fffffff
tmp.start 120000000, tmp.end ffffffffffffffff
pci 0000:00:04.0: BAR 2: assigned [mem 0x140000000-0x17fffffff 64bit]
and when it fails with a 2GB BAR, the following is printed
this->start 1000, this->end 9f3ff
this->start 9f400, this->end 9ffff
this->start f0000, this->end fffff
this->start 100000, this->end dfffcfff
this->start dfffd000, this->end dfffffff
pci 0000:00:04.0: BAR 2: can't assign mem (size 0x80000000)
I added a few more debug statements and found that in the failure case, the function returns that it found a region (the last one printed before the error). I've added printfs for the two tests in the if that determine when a region is found:
if (tmp.start < tmp.end && tmp.end - tmp.start >= size - 1) {
new->start = tmp.start;
new->end = tmp.start + size - 1;
printk(KERN_INFO "returning 0\n");
return 0;
}
this->start 1000, this->end 9f3ff
tmp.start 80000000, tmp.end fff
true: ffffffff80000fff >= 7fffffff
this->start 9f400, this->end 9ffff
tmp.start 80000000, tmp.end 9f3ff
true: ffffffff8009f3ff >= 7fffffff
this->start f0000, this->end fffff
tmp.start 80000000, tmp.end effff
true: ffffffff800effff >= 7fffffff
this->start 100000, this->end dfffcfff
tmp.start 80000000, tmp.end fffff
true: ffffffff800fffff >= 7fffffff
this->start dfffd000, this->end dfffffff
tmp.start 100000, tmp.end dfffcfff
true: 100000 < dfffcfff
true: dfefcfff >= 7fffffff
returning 0
pci 0000:00:04.0: BAR 2: can't assign mem (size 0x80000000)
--
error compiling committee.c: too many arguments to function