Re: [Xen-devel] [PATCH v2] xen-hvm: stop faking I/O to access PCI config space

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.05.18 at 15:51, <Paul.Durrant@xxxxxxxxxx> wrote:
>> Sent: 18 May 2018 14:34
>> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
>> >>> On 18.05.18 at 15:00, <paul.durrant@xxxxxxxxxx> wrote:
>> > +    QLIST_FOREACH(xendev, &state->dev_list, entry) {
>> > +        unsigned int i;
>> > +        uint32_t tmp;
>> > +
>> > +        if (xendev->sbdf != sbdf) {
>> > +            continue;
>> > +        }
>> > +
>> > +        if (!req->data_is_ptr) {
>> > +            if (req->dir == IOREQ_READ) {
>> > +                for (i = 0; i < req->count; i++) {
>> > +                    rw_config_req_item(xendev, req, i, &tmp);
>> > +                    req->data = tmp;
>> > +                }
>> > +            } else if (req->dir == IOREQ_WRITE) {
>> > +                for (i = 0; i < req->count; i++) {
>> > +                    tmp = req->data;
>> > +                    rw_config_req_item(xendev, req, i, &tmp);
>> > +                }
>> > +            }
>> 
>> Wouldn't it be more sensible to fail req->count != 1 requests here?
>> 
> 
> I'm wondering whether we'd want to handle count > 1 once we allow MMCONFIG 
> accesses though. I guess it would be easier just to defer that.

For the data_is_ptr case - sure. But here? Or wait - are you thinking about
REP STOS (and the relatively useless REP LODS)?

Jan



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