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Re: [Xen-devel] Xen 4.3 development update RC2 imminent

Il 21/05/2013 18:16, George Dunlap ha scritto:
On 05/21/2013 05:13 PM, George Dunlap wrote:
On 05/21/2013 03:55 PM, Jan Beulich wrote:
On 21.05.13 at 16:31, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
On 21/05/13 15:06, Anthony PERARD wrote:
But then, once this applied, qxl is still not able to start. Xorg crash
(in the guest), and here is why:

(XEN) emulate.c:88:d18 bad mmio size 16
(XEN) io.c:201:d18 MMIO emulation failed @ 0033:7fd2de390430: f3 0f 6f
19 41 83 e8 403
(XEN) emulate.c:88:d18 bad mmio size 16
(XEN) io.c:201:d18 MMIO emulation failed @ 0033:7fd2de390430: f3 0f 6f
19 41 83 e8 403

Disassembly of section .data:

0000000000000000 <.data>:
    0:    f3 0f 6f 19              movdqu (%rcx),%xmm3

Xen does not support emulating SSE instructions.  We have sporadically
seen similar errors from Windows guests. The best guess I have managed to get so far is that %rcx is a pointer to something which Xen thinks is
an MMIO page.

In this case, it looks like X is copying from MMIO into an xmm register,
scraping the framebuffer perhaps?  In the windows failure, it was the
pagescrub trying to zero ram, which clearly indicated something wonky in
the combined idea of the memory map.

If Spice is doing something valid and sensible, then Xen will likely
need extending to be able to emulate SSE instructions.

The emulator in the hypervisor can handle simple SSE instructions
like the above quite well. It's not immediately clear to me why
hvmemul_do_io() would need to limit the size to no more than a
long's width. Perhaps the data passing to the device model may
need adjustment to accommodate wider entities...

Hmm, but the code seems to indicate that the DM can handle wider
entities, by "reading all ones":

         if ( dir == IOREQ_READ )
             memset(p_data, ~0, size);

Anthony, do you want to try making that size check one size bigger
(e.g., allow it to be 16 or 32)?

No, that obviously won't work, because of the line just following:

    if ( (p_data != NULL) && (dir == IOREQ_WRITE) )
        memcpy(&value, p_data, size);
        p_data = NULL;

value is of size "long", so this won't work.

Thanks for help to solve this problem.
Are there news about?

Probably this is a stupid question: is this patch related to that problem?

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