Re: [PATCH 2/2] Do not access /dev/mem in MSI-X PCI passthrough on Xen

[Jan Beulich]

On 14.11.2022 20:20, Marek Marczykowski-Górecki wrote:
> The /dev/mem is used for two purposes:
>  - reading PCI_MSIX_ENTRY_CTRL_MASKBIT
>  - reading Pending Bit Array (PBA)
> 
> The first one was originally done because when Xen did not send all
> vector ctrl writes to the device model, so QEMU might have outdated old
> register value. This has been changed in Xen, so QEMU can now use its
> cached value of the register instead.
> 
> The Pending Bit Array (PBA) handling is for the case where it lives on
> the same page as the MSI-X table itself. Xen has been extended to handle
> this case too (as well as other registers that may live on those pages),
> so QEMU handling is not necessary anymore.

Don't you need to check for new enough Xen for both aspects?

Jan