Re: [PATCH V4 1/3] efi: Determine how much space is used by bootservices-only variables

From: Lingzhu Xiang
Date: Fri Apr 12 2013 - 08:19:37 EST

On 04/11/2013 01:46 AM, Matthew Garrett wrote:
EFI variables can be flagged as being accessible only within boot services.
This makes it awkward for us to figure out how much space they use at
runtime. In theory we could figure this out by simply comparing the results
from QueryVariableInfo() to the space used by all of our variables, but
that fails if the platform doesn't garbage collect on every boot. Thankfully,
calling QueryVariableInfo() while still inside boot services gives a more
reliable answer. This patch passes that information from the EFI boot stub
up to the efivars code, letting us calculate a reasonably accurate value.

Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>

I just tried this 3.9-rc6 with this patchset with pstore fulling up space and various attempts to manually fulling up space. So far I've been able to delete variables and continue creating variables.

Since QueryVariableInfo is no longer trusted and the accounting is done by the kernel, I'm somewhat concerned that variables can be repeatedly created and deleted until nvram is full of garbage to collect and the firmware hits EFI_OUT_OF_RESOURCES. Could this be any kind of problem?

Lingzhu Xiang
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