[dm-devel] HPA unlock during partition scan of RAID components

[Phillip Susi]

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On 11/04/2011 09:43 PM, Tejun Heo wrote:
> Yes, it would break under windows and it does.  Get a motherboard 
> which always locks HPA, do hotplug, create filesystem filling the
> full disk and reboot. BIOS doesn't have a reliable way of
> determining whether the disk is "unformatted" or not. Some try to
> scan dos partition table but filesystem may be created on the whole
> device or software raid could be using the whole drive. There is no
> reliable way to tell. Some BIOSen may try to do HPA locking after
> hotplug using ACPI _GTF which in theory can work but in practice
> many motherboards either don't implement them or are horridly
> broken. So, yeah, it isn't too difficult to break whether the os is
> windows or linux.

Well if it breaks under Windows, then we can't be faulted for having
the same results now can we?

> The only argument against unlocking by default and providing both 
> sizes is that some BIOSen may act incorrectly after soft reset,
> which seems acceptable provided there's an override to disable the
> automatic unlocking.

The other argument is that unlocking by default trashes whatever data
the bios was trying to hide in the HPA, and deviates from the behavior
of Windows.

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