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.
prev parent 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]
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