Hello Zhenzhong
On 11/20/23 11:07, Duan, Zhenzhong wrote:
Hi Cédric,
-----Original Message-----
From: Cédric Le Goater <c...@redhat.com>
Sent: Monday, November 20, 2023 4:25 PM
Subject: Re: [PATCH v6 01/21] backends/iommufd: Introduce the iommufd object
A similar issue with a fix submitted below, ccing related people.
https://lists.gnu.org/archive/html/qemu-devel/2023-11/msg02937.html
It looks the fix will not work for hotplug.
Or below qemu cmdline may help:
"-cpu host,host-phys-bits-limit=39"
don't you have the same issue with legacy VFIO code, you should?
I tend to be lazy and use seabios for guests on the command line.
I do see the error with legacy VFIO and uefi.
However, with the address space size work-around and iommufd, the
error is different, an EFAULT now. Some page pinning issue it seems.
Yes, this reminds me of iommufd not supporting p2p mapping yet.
OK. Should we transform this error in a warning ? The code needs
at least a comment.
Make sense, though I'm not clear if there is other corner case return EFAULT.
yep. That's the problem.
I plan below change in v7:
diff --git a/backends/iommufd.c b/backends/iommufd.c
index 53fdac4cc0..ba58a0eb0d 100644
--- a/backends/iommufd.c
+++ b/backends/iommufd.c
@@ -178,7 +178,13 @@ int iommufd_backend_map_dma(IOMMUFDBackend *be, uint32_t
ioas_id, hwaddr iova,
vaddr, readonly, ret);
if (ret) {
ret = -errno;
- error_report("IOMMU_IOAS_MAP failed: %m");
+
+ /* TODO: Not support mapping hardware PCI BAR region for now. */
+ if (errno == EFAULT) {
+ warn_report("IOMMU_IOAS_MAP failed: %m, PCI BAR?");
+ } else {
+ error_report("IOMMU_IOAS_MAP failed: %m");
+ }
}
return ret;
}
I failed to change vfio_container_dma_map print as warning because for legacy
container, it's real errro.
So print after fix:
qemu-system-x86_64: warning: IOMMU_IOAS_MAP failed: Bad address, PCI BAR?
qemu-system-x86_64: vfio_container_dma_map(0x560cb6cb1620, 0xe000000021000,
0x3000, 0x7f32ed55c000) = -14 (Bad address)
I am OK with that. Let's see what the others have to say.
So EFAULT is expected. Maybe I should add a comment in docs/devel/vfio-
iommufd.rst
Yes. It would be good to have a list of gaps and effects in the
documentation. See Jason's presentation at LPC.
https://lpc.events/event/17/contributions/1418/attachments/1297/2607/LPC202
3_iommufd.pdf
I see, PCI Peer to Peer and POWER/SPAPR are related to qemu iommufd
implementation.
For POWER/SPAPR, we have "Supported platform" section.
yes.
Below are other gaps I can think of for now:
Gaps:
1. dirty page sync, WIP (Joao)
2. p2p dma not supported yet.
3. fd passing with mdev not support ram discard(vfio-pci) as no way to know
it's a mdev from a fd.
Call the section Caveats maybe?
Thanks,
C.
