[PATCH] pci: advertise a page aligned ATS

[Jason Wang]

After Linux kernel commit 61363c1474b1 ("iommu/vt-d: Enable ATS only
if the device uses page aligned address."), ATS will be only enabled
if device advertises a page aligned request.

Unfortunately, vhost-net is the only user and we don't advertise the
aligned request capability in the past since both vhost IOTLB and
address_space_get_iotlb_entry() can support non page aligned request.

Though it's not clear that if the above kernel commit makes
sense. Let's advertise a page aligned ATS here to make vhost device
IOTLB work with Intel IOMMU again.

Note that in the future we may extend pcie_ats_init() to accept
parameters like queue depth and page alignment.

Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/pci/pcie.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index 5b48bae0f6..d4010cf8f3 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -971,8 +971,9 @@ void pcie_ats_init(PCIDevice *dev, uint16_t offset)
 
     dev->exp.ats_cap = offset;
 
-    /* Invalidate Queue Depth 0, Page Aligned Request 0 */
-    pci_set_word(dev->config + offset + PCI_ATS_CAP, 0);
+    /* Invalidate Queue Depth 0, Page Aligned Request 1 */
+    pci_set_word(dev->config + offset + PCI_ATS_CAP,
+                 PCI_ATS_CAP_PAGE_ALIGNED);
     /* STU 0, Disabled by default */
     pci_set_word(dev->config + offset + PCI_ATS_CTRL, 0);
 
-- 
2.20.1