@@ -1783,9 +1783,17 @@ static int ehci_state_fetchqtd(EHCIQueue *q)
EHCIqtd qtd;
EHCIPacket *p;
int again = 1;
+ uint32_t addr;
- if (get_dwords(q->ehci, NLPTR_GET(q->qtdaddr), (uint32_t *) &qtd,
- sizeof(EHCIqtd) >> 2) < 0) {
+ addr = NLPTR_GET(q->qtdaddr);
+ if (get_dwords(q->ehci, addr + 8, &qtd.token, 1) < 0) {
+ return 0;
+ }
+ barrier();
+ if (get_dwords(q->ehci, addr + 0, &qtd.next, 1) < 0 ||
+ get_dwords(q->ehci, addr + 4, &qtd.altnext, 1) < 0 ||
+ get_dwords(q->ehci, addr + 12, qtd.bufptr,
+ ARRAY_SIZE(qtd.bufptr)) < 0) {
return 0;
}
ehci_trace_qtd(q, NLPTR_GET(q->qtdaddr), &qtd);
The token field contains the (guest-filled) state of the qtd, which indicates whenever the other fields are valid or not. So make sure we read the token first, otherwise we may end up with an stale next pointer: (1) ehci reads next (2) guest writes next (3) guest writes token (4) ehci reads token (5) ehci operates with stale next. Typical effect is that qemu doesn't notice that the guest appends new qtds to the end of the queue. Looks like the usb device stopped responding. Linux can recover from that, but leaves a message in the kernel log that it did reset the usb device in question. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Message-id: 20181126100836.8805-1-kraxel@redhat.com --- hw/usb/hcd-ehci.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)