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usb: Fix usb_packet_map() in the presence of IOMMUs 

With the IOMMU infrastructure introduced before 1.2, we need to use
dma_memory_map() to obtain a qemu pointer to memory from an IO bus address.
However, dma_memory_map() alters the given length to reflect the length
over which the used DMA translation is valid - which could be either more
or less than the requested length.

usb_packet_map() does not correctly handle these cases, simply failing if
dma_memory_map() alters the requested length.  If dma_memory_map()
increased the length, we just need to use the requested length for the
qemu_iovec_add().  However, if it decreased the length, it means that a
single DMA translation is not valid for the whole sglist element, and so
we need to loop, splitting it up into multiple iovec entries for each
piece with a DMA translation (in practice >2 pieces is unlikely).

This patch implements the correct behaviour

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
David Gibson 2012-09-26 12:59:31 +10:00 committed by Gerd Hoffmann
parent 8b626aa784
commit 39c138c842
1 changed files with 15 additions and 9 deletions
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24
hw/usb/libhw.c
View File

@ -28,19 +28,25 @@ int usb_packet_map(USBPacket *p, QEMUSGList *sgl)
{
DMADirection dir = (p->pid == USB_TOKEN_IN) ?
DMA_DIRECTION_FROM_DEVICE : DMA_DIRECTION_TO_DEVICE;
dma_addr_t len;
void *mem;
int i;
for (i = 0; i < sgl->nsg; i++) {
len = sgl->sg[i].len;
mem = dma_memory_map(sgl->dma, sgl->sg[i].base, &len, dir);
if (!mem) {
goto err;
}
qemu_iovec_add(&p->iov, mem, len);
if (len != sgl->sg[i].len) {
goto err;
dma_addr_t base = sgl->sg[i].base;
dma_addr_t len = sgl->sg[i].len;
while (len) {
dma_addr_t xlen = len;
mem = dma_memory_map(sgl->dma, sgl->sg[i].base, &xlen, dir);
if (!mem) {
goto err;
}
if (xlen > len) {
xlen = len;
}
qemu_iovec_add(&p->iov, mem, xlen);
len -= xlen;
base += xlen;
}
}
return 0;