[Skiboot] [PATCH v4 04/11] doc: add opal secure variable documentation
mpe at ellerman.id.au
Sat Nov 2 22:15:41 AEDT 2019
"Oliver O'Halloran" <oohall at gmail.com> writes:
> On Thu, Oct 31, 2019 at 2:07 PM Eric Richter <erichte at linux.ibm.com> wrote:
>> On 10/30/19 9:46 PM, Michael Ellerman wrote:
>> > Eric Richter <erichte at linux.ibm.com> writes:
>> >> On 10/28/19 10:47 PM, Michael Ellerman wrote:
>> >>> Eric Richter <erichte at linux.ibm.com> writes:
>> > ...
>> >>>> + update-status: contains the return code of the update queue
>> >>>> + process run during initialization. Signifies if
>> >>>> + updates were processed or not, and if there was
>> >>>> + an error. See table below.
>> >>> Encoded how? I assume you mean as a u32, but please say so.
>> >>> This is a bit weird, encoding an OPAL return value in a property. I
>> >>> don't understand how the kernel is going to use it. I don't see any
>> >>> patches posted yet that use it?
>> >> It is a u64, will update to mention that.
>> >> This isn't a property intended for the kernel to consume, meant for exposing
>> >> to userspace the status of update. Update processing is handled at boot, so
>> >> outside of writing to a log, it seemed like the best way to signal status
>> >> to a user.
>> > But are we expecting a user to look at the device tree to find the
>> > status? That seems suboptimal.
>> We don't currently have any tools that check for this, but this information
>> should be available. Ideally, a script, or petitboot should report the status
>> of the update to the user.
> Sounds kind of janky, but whatever. I'm fine with this provided we do
> enough pre-validation of updates to ensure that we should never see an
> update failure unless the PNOR has been tampered with.
>> >> As for the use of OPAL codes: they were convenient to use as they matched the
>> >> error cases that likely all backends will share. Would it be more clear to
>> >> define a new set of return codes, or represent this information in a
>> >> different way?
>> > Using the OPAL codes is fine, if the kernel is going to consume them.
>> If the value is exposed in sysfs, should the kernel translate the value to
>> something else? A Linux/POSIX error code or a user-friendly string?
> I don't have any strong opinions about what the encoding should be,
> but but don't use Linux or POSIX errno values. We try to maintain the
> pretense of OPAL being OS-independent so baking in Linux return codes
> isn't acceptable. I'm also fairly sure POSIX doesn't actually specify
> the values of the error codes, just their symbolic names. Either stick
> with what you're currently doing and use the OPAL codes, defines a new
> enum for secvar specific errors or put in a string.
Let's just go with OPAL codes.
The kernel can either interpret them before exposing them via sysfs, or
we document that the sysfs API is using OPAL error codes for this
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