Re: [PATCH v2 0/3] PCI/IOV: Restore initial VF BAR sizing after VF ReBAR

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From: Simon Richter

Date: Mon Aug 03 2026 - 07:32:40 EST

Hi,

On 8/3/26 7:30 PM, Marcin Bernatowicz wrote:

PF drivers can resize a VF BAR using VF Resizable BAR (ReBAR) support via
pci_iov_vf_bar_set_size(). The new size persists in the SR-IOV capability
config space. A later reprobe / unplug-rescan / next pci_enable_sriov()
then sees the inflated VF BAR registers, and the PCI core reserves MMIO
based on that size multiplied by TotalVFs.

Would it make sense for pci_enable_sriov() to check for a ReBAR capability in the VF and set it to the smallest possible setting, so we get the same behaviour regardless of whether this was cleaned up correctly?

Also, should it be "previous" or "smallest" size (in order to not make a missed cleanup permanent)?

I'm a bit worried about POWER, while we do have lots of MMIO space, we also use kexec() quite a lot because on several machines, the bootloader is some ancient minimal Linux system.

Simon