On Sun, Feb 19, 2012 at 13:35, Michael S. Tsirkin <m...@redhat.com> wrote:
> On Fri, Feb 17, 2012 at 05:08:40PM +0000, Anthony PERARD wrote:
>> From: Yuji Shimada <shimada-...@necst.nec.co.jp>
>>
>> This function helps Xen PCI Passthrough device to check for overlap.
>>
>> Signed-off-by: Yuji Shimada <shimada-...@necst.nec.co.jp>
>> Signed-off-by: Anthony PERARD <anthony.per...@citrix.com>
>
> As far as I can see, this scans the bus a specific
> device is on, looking for devices who have conflicting
> BARs. Returns 1 if found, 0 if not.
>
> Not sure what would devices do with this information, really:
> patches posted just print out a warning which does not seem
> too useful.
This function is just here to print a warning in case an overlap
happen, but we would like too keep this warning.
> Just FYI, if you decided to e.g. disable device in
> such a case that would be wrong: it is legal to have overlapping BARs as
> long as there are no accesses.
> So a legal thing for a guest to do is:
>
> Assign BAR1 = abcde
> Assign BAR2 = abcde <- overlaps temporarily
> Assign BAR1 = 12345
>
> And this means that you can't just check your device
> has no conflicts when your device is touched:
> it needs to be checked each time mappings are updated.
>
>> ---
>> hw/pci.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
>> hw/pci.h | 3 +++
>> 2 files changed, 50 insertions(+), 0 deletions(-)
>>
>> diff --git a/hw/pci.c b/hw/pci.c
>> index 678a8c1..75d6529 100644
>> --- a/hw/pci.c
>> +++ b/hw/pci.c
>> @@ -1985,6 +1985,53 @@ MemoryRegion *pci_address_space_io(PCIDevice *dev)
>> return dev->bus->address_space_io;
>> }
>>
>> +int pci_check_bar_overlap(PCIDevice *dev,
>> + pcibus_t addr, pcibus_t size, uint8_t type)
>
> This lacks comments documentng what this does, parameters, return
> values, etc.
I'll fix that.
>> +{
>> + PCIBus *bus = dev->bus;
>> + PCIDevice *devices = NULL;
>> + PCIIORegion *r;
>> + int i, j;
>> + int rc = 0;
>> +
>> + /* check Overlapped to Base Address */
>
> Weird use of upper case. Intentional?
> Also - what does this comment mean?
Don't know, I will remove the comment, it is useless.
>> + for (i = 0; i < ARRAY_SIZE(bus->devices); i++) {
>> + devices = bus->devices[i];
>> + if (!devices) {
>> + continue;
>> + }
>> +
>> + /* skip itself */
>
> itself?
Same here, the comment is probably useless, the next line should be
easy to understand.
>> + if (devices->devfn == dev->devfn) {
>> + continue;
>> + }
>> +
>> + for (j = 0; j < PCI_NUM_REGIONS; j++) {
>
> This ignores bridges.
I'm not familiar with brigdes. I'll try to take a look.
>> + r = &devices->io_regions[j];
>> +
>> + /* skip different resource type, but don't skip when
>> + * prefetch and non-prefetch memory are compared.
>> + */
>> + if (type != r->type) {
>> + if (type & PCI_BASE_ADDRESS_SPACE_IO ||
>> + r->type & PCI_BASE_ADDRESS_SPACE_IO) {
>
> Do you mean
> type & PCI_BASE_ADDRESS_SPACE_IO != r->type &
> PCI_BASE_ADDRESS_SPACE_IO
> ?
>
> This would not need a comment then.
Yes, I'll replace that.
>
>> + continue;
>> + }
>> + }
>> +
>> + if ((addr < (r->addr + r->size)) && ((addr + size) > r->addr)) {
>
> Can ranges_overlap be used?
Yes.
>> + printf("Overlapped to device[%02x:%02x.%x][Region:%d]"
>> + "[Address:%"PRIx64"h][Size:%"PRIx64"h]\n",
>> + pci_bus_num(bus), PCI_SLOT(devices->devfn),
>> + PCI_FUNC(devices->devfn), j, r->addr, r->size);
>
>
> That's not how one should report errors.
A callback would be better?
Thanks,
--
Anthony PERARD
