Re: [PATCH V1 0/5] UEFI Variable SMI Reduction

["Laszlo Ersek" <lersek@redhat.com>]

On 10/01/19 00:43, Laszlo Ersek wrote:
> On 09/27/19 00:35, Kubacki, Michael A wrote:
>> After thinking a bit more, this test is based on a side effect of implementation. I'd prefer to avoid this being the sole cause of additional complexity in an already complex driver. Are one of these two options acceptable?
>>
>> 1. Use the Runtime Services QueryVariableInfo () API
>>
>> In this patch series, this is still implemented to trigger an SMI as invocations occur very rarely outside mainstream GetVariable () and GetNextVariableName () usage so performance is not a major concern. This allows it to continue to use the validated path to the converged implementation in Variable.c
> 
> QueryVariableInfo() is not exposed to Linux userspace in any practical way.
> 
> The Firmware Test Suite contains a dedicated test case for that runtime
> service:
> 
> https://wiki.ubuntu.com/FirmwareTestSuite/Reference/uefivarinfo
> 
> which can be invoked from the root prompt.
> 
> However, the userspace app depends on the efi_test module
> (CONFIG_EFI_TEST), which is not built in Fedora (not even in the debug
> kernel).
> 
> Building the kernel module specifically for the test is very messy,
> especially if the running kernel was signed, and booted with Secure Boot
> enabled. (It won't just accept any hand-build module.)
> 
> I'll ask the Fedora kernel maintainers if they can set CONFIG_EFI_TEST
> to "m".

NB, using QueryVariableInfo() for testing would still rely on an
implementation detail, namely that QueryVariableInfo() is allowed (for
now) to enter SMM.

But what if that changes again?

Thanks
Laszlo