[gPXE] [PATCH] [pciextra] Restore the PCI COMMAND register after writing to the BARs

[Shao Miller]

Bernhard Kohl wrote:
>
> Hi,
>
> This seems to be necessary for some types of PCI devices. We got problems
> when using gPXE in KVM virtual machines with direct PCI device access.
>
> The PCI spec says:
> Decode (I/O or memory) of a register is disabled via the command
> register before
> sizing a Base Address register. Software saves the original value of the
> Base
> Address register, writes 0FFFFFFFFh to the register, then reads it back.
> ...
> The original value in the Base Address register is restored before
> reenabling
> decode in the command register of the device.
>
Thanks, Bernhard.  This has been noted at 
http://support.etherboot.org/index.php?do=details&task_id=40

- Shao Miller
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