[Xen-devel] stdvga: slow ioreq

["Christoph Egger" <Christoph.Egger@xxxxxxx>]

Hello Ropert!

Since changeset 16285 (xen-staging), I get the following output when I launch
a HVM guest and VGABios is running:

---------------------------------------------------------------------------------------
(XEN) intercept.c:172:d1 slow ioreq. type:1 size:1 addr:0xa0000 dir:0 ptr:1 
df:0 count:16
(XEN) intercept.c:172:d1 slow ioreq. type:1 size:1 addr:0xa0020 dir:0 ptr:1 
df:0 count:16
(XEN) intercept.c:172:d1 slow ioreq. type:1 size:1 addr:0xa0040 dir:0 ptr:1 
df:0 count:16
(XEN) intercept.c:172:d1 slow ioreq. type:1 size:1 addr:0xa0060 dir:0 ptr:1 
df:0 count:16
(XEN) intercept.c:172:d1 slow ioreq. type:1 size:1 addr:0xa0080 dir:0 ptr:1 
df:0 count:16
(XEN) intercept.c:172:d1 slow ioreq. type:1 size:1 addr:0xa00a0 dir:0 ptr:1 
df:0 count:16
[...]
(XEN) intercept.c:172:d1 slow ioreq. type:1 size:1 addr:0xa1fe0 dir:0 ptr:1 
df:0 count:16
------------------------------------------------------------------------------------------

This is not the full output (to keep this mail readable). The address output
starts from 0xa0000 and goes to 0xa1fe0 and it always increases by 0x20.
(So you can generate the full output yourself :)

The output comes from xen/arch/x86/intercept.c, function 
hvm_buffered_io_send().
It is this code snippet:

    /* Return 0 for the cases we can't deal with. */
    if ( (p->addr > 0xffffful) || p->data_is_ptr || p->df || (p->count != 1) )
    {
        gdprintk(XENLOG_DEBUG, "slow ioreq. type:%d size:%"PRIu64" addr:0x%"
                 PRIx64" dir:%d ptr:%d df:%d count:%"PRIu64"\n",
                 p->type, p->size, p->addr, !!p->dir,
                 !!p->data_is_ptr, !!p->df, p->count);
        return 0;
    }

It looks like the problem was there before changeset 16285 but got uncovered
with the addition of the debug output.

Christoph


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Operating System Research Center

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