DPDK usage discussions
 help / color / mirror / Atom feed
From: Stephen Hemminger <stephen@networkplumber.org>
To: Oleksandr Nahnybida <oleksandrn@interfacemasters.com>
Cc: users <users@dpdk.org>,
	Vitaliy Ivanov <vitaliyi@interfacemasters.com>,
	Taras Bilous <tarasb@interfacemasters.com>
Subject: Re: How to use vfio-pci in vmware VM with PCI passthrough?
Date: Wed, 15 Oct 2025 10:40:06 -0700	[thread overview]
Message-ID: <20251015104006.319fa83a@hermes.local> (raw)
In-Reply-To: <CAAFk=6Dfs3tKhU3VbLu-4xn3JtyNvnDaAk52p8GMpL05Ojn8rA@mail.gmail.com>

On Thu, 2 Oct 2025 17:40:07 +0300
Oleksandr Nahnybida <oleksandrn@interfacemasters.com> wrote:

> Hi all,
> 
> We are working on migrating our DPDK application from igb_uio to vfio-pci.
> Our target environment is a VMware ESXi host running on an AMD Epyc server
> with NICs configured for PCI Passthrough to a guest VM with Debian Bookworm
> (Kernel 6.1.0-39-amd64)
> 
> We've encountered a couple of issues.
> 
> Problem 1:
> 
> Initially, attempting to use vfio-pci failed with an error code of -22, and
> the /sys/class/iommu/ directory was empty. We discovered the "expose IOMMU
> to guest OS" option in VMware and enabled it.
> 
> This led to a new error:
> "The virtual machine cannot be powered on because IOMMU virtualization is
> not compatible with PCI passthru on AMD platforms"
> 
> We found a workaround by adding amd.iommu.supportsPcip = "TRUE" to the VM's
> configuration. The VM now boots, and the IOMMU is visible in the guest.
> 
> However, when we run our DPDK application, it hangs after printing "EAL:
> VFIO support initialized", and shortly after, the guest kernel panics with
> a soft lockup error, making the system eventually unresponsive.
> BUG: soft lockup - CPU#34 stuck for 75s! [kcompactd0:529]
> 
> Problem 2:
> 
> Separately, we've noticed that our IOMMU groups are not ideal. Many groups
> contain not only the NICs we need to bind, but also other devices like PCI
> bridges.
> 
> IOMMU Group 7:
>         0000:00:17.0 - PCI bridge: VMware PCI Express Root Port
>         0000:00:17.1
>         0000:00:17.2
>         0000:00:17.3
>         0000:00:17.4
>         0000:00:17.5
>         0000:00:17.6
>         0000:00:17.7
>         0000:13:00.0 - nic
>         0000:13:00.1 - nic
>         0000:14:00.0 - nic
>         0000:14:00.1 - nic
> 
> Questions:
> 
>    1.  Is enabling guest IOMMU virtualization in VMware with the
>    amd.iommu.supportsPcip workaround, the correct approach here?
>    2. I see that vfio-pci can be run in unsafe mode, but is there any
>    benefit to using it over igb_uio in this case?
>       1. In my understanding, the hypervisor is using actual hardware IOMMU
>       to implement PCI pass-through anyway, so what's the point of having it
>       inside of a guest VM again?
>       2. Also, usually enable_unsafe_noiommu_mode is not compiled in, so we
>       need to recompile vfio separately, and since we already compile igb_uio
>       anyway, vfio won't be any better in terms of deployment.
>    3. There also seems to be an option of using SR-IOV instead of
>    passthrough, but we haven't explored this option yet. The question here is,
>    do you still need to "expose iommu" to be able to bind VF to vfio? And
>    what's the correct workflow here in general?
> 
> Best Regarads,
> Oleksandr

You may have to use vfio-pci without iommu option.

      reply	other threads:[~2025-10-15 17:40 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-10-02 14:40 Oleksandr Nahnybida
2025-10-15 17:40 ` Stephen Hemminger [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20251015104006.319fa83a@hermes.local \
    --to=stephen@networkplumber.org \
    --cc=oleksandrn@interfacemasters.com \
    --cc=tarasb@interfacemasters.com \
    --cc=users@dpdk.org \
    --cc=vitaliyi@interfacemasters.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).