Comments below.
> -----Original Message-----
> From: Laszlo Ersek [mailto:ler...@redhat.com]
> Sent: Thursday, November 23, 2017 10:03 PM
> To: Ni, Ruiyu <ruiyu...@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>
> Cc: Ard Biesheuvel <ard.biesheu...@linaro.org>; Justen, Jordan L
> <jordan.l.jus...@intel.com>; Dong, Eric <eric.d...@intel.com>; Zeng, Star
> <star.z...@intel.com>; Doran, Mark <mark.do...@intel.com>
> Subject: Re: [PATCH 3/5] MdeModulePkg/UefiBootManagerLib: report
> EDKII_OS_LOADER_DETAIL status code
>
> Hello Ray,
>
> (CC Mark Doran for the last part of my email)
>
> On 11/23/17 06:21, Ni, Ruiyu wrote:
> > Laszlo,
> > When booting a boot option, UefiBootManagerBoot() sets a Boot####
> > variable and saves #### to BootCurrent variable.
> > So all the details (except the EDKII_OS_LOADER_DETAIL.Status) can be
> > retrieved from reading Boot#### variable.
>
> I have two counter-arguments:
>
> (1) I would like to minimize the number of accesses to non-volatile UEFI
> variables. Dependent on the virtualization platform and the (virtual) flash
> chip
> structure (for example, flash block size), flash access can be very slow.
>
> I'm not 100% sure whether this performance problem affects flash *reads* as
> well, or if it affects flash writes only. (It definitely affects flash
> writes.)
NV *read* should have no performance impact since EDKII variable driver's
implementation caches the flash in memory. I am not sure about that
in OVMF. But I think a good implementation of variable driver should
consider such *read* optimization.
Performance needs to be considered, but simpler/easy-maintain
code takes higher priority.
>
>
> (2) The delivery of status codes to registered handlers is asynchronous, not
> synchronous. Handlers are registered at various task priority levels, and if
> the
> reporting occurs at the same or higher TPL, then the delivery will be delayed.
> (According to the PI spec, it is even possible to report several status codes
> before the first will be delivered -- basically the codes are queued until
> the TPL is
> reduced sufficiently.) This is why all data has to be embedded in the status
> code
> structure itself.
>
> Like in any other notify function's case, it is prudent to register status
> code
> handlers at the least strict TPL that can work for the actual processing. (The
> internals of the handler function can even put an upper limit on the TPL; for
> example using Simple Text Output prevents us from going higher than
> TPL_NOTIFY.) For this reason I chose TPL_CALLBACK for the OVMF status code
> handler.
>
> Now, if we can *guarantee* that these status codes are only reported at the
> TPL_APPLICATION level, then a TPL_CALLBACK status code handler will be
> synchronous in effect, and then the status code structure can carry references
> to other (external) things in the system too, such as UEFI variables.
>
> Can we guarantee that EfiBootManagerBoot() is never invoked above
> TPL_APPLICATION?
Yes. It should be. Because gBS->LoadImage()/StartImage() per UEFI spec TPL
restriction rule, should be run at TPL_APPLICATION.
And if there is no special reason (handler runs too slow), the status handler
is registered at TPL_HIGH so that the handler is called synchronously.
>
> >
> > 4 more comments below.
>
> [snip]
>
> >> + BmReportOsLoaderDetail (
> >> + OsLoaderDetail,
> >> + OsLoaderDetailSize,
> >> + EDKII_OS_LOADER_DETAIL_TYPE_LOAD,
> >> + 0 // DetailStatus -- unused here
> >> + );
> >> +
> >
> > 1. With the BootCurrent, this change is not necessary because others
> > can hook PcdProgressCodeOsLoaderLoad to get the current loading boot
> > option.
>
> As long as we can clear my points (1) and (2) above, I'd be fine with this
> approach.
>
> >
> >> Status = gBS->LoadImage (
> >> TRUE,
> >> gImageHandle,
> >> FilePath,
> >> FileBuffer,
> >> FileSize,
> >> &ImageHandle
> >> );
> >> }
> >> if (FileBuffer != NULL) {
> >> FreePool (FileBuffer);
> >> }
> >> if (FilePath != NULL) {
> >> FreePool (FilePath);
> >> }
> >>
> >> if (EFI_ERROR (Status)) {
> >> //
> >> // Report Status Code to indicate that the failure to load boot
> >> option
> >> //
> >> REPORT_STATUS_CODE (
> >> EFI_ERROR_CODE | EFI_ERROR_MINOR,
> >> (EFI_SOFTWARE_DXE_BS_DRIVER |
> >> EFI_SW_DXE_BS_EC_BOOT_OPTION_LOAD_ERROR)
> >> );
> >> + BmReportOsLoaderDetail (
> >> + OsLoaderDetail,
> >> + OsLoaderDetailSize,
> >> + EDKII_OS_LOADER_DETAIL_TYPE_LOAD_ERROR,
> >> + Status
> >> + );
> >> +
> >
> > 2. I think firstly, the OsLoaderDetail is not needed.
> > Secondly, I prefer to submit a PI spec change to include extended data
> > for EFI_SW_DXE_BS_EC_BOOT_OPTION_LOAD_ERROR status code.
> > Instead of inventing a new status code.
>
> I understand your point, and in theory I agree with it, but in practice, I
> cannot.
If there is no similar status code for a certain purpose, I agree to invent a
new status
code. And when the new status code is proven by time to be mature enough, it
can go
to PI spec.
But for this case, since PI spec already has such status code, I prefer to at
least try
to change the spec. If PIWG doesn't agree, we can go on using the new status
code.
>
> My experience with Mantis tickets is not good:
>
> (a) First, I would have to write up the proposal. That's fine, I can do that;
> have
> done it before.
>
>
> (b) Second, I'd have to *call* the meetings. Please locate the email titled
>
> a reminder about MANTIS usage
>
> from Mark, (date: 6 Sep 2017), cross-posted to the PIWG/USWG/ASWG lists.
>
> I'm not allowed to quote the email verbatim -- all of these lists are
> confidential -
> -, but if you look up the paragraph starting with "Best practice", Mark
> basically
> implied, "file the the Mantis ticket, then dial in to the next meeting and
> sell your
> proposal to the WG *verbally*".
>
> I *cannot* do that. The WG meetings always take place early afternoon in
> Pacific (US West Coast) timezone, which is around *midnight* in my timezone.
>
> In addition, I don't even have time to attend the confcalls that I'm invited
> to
> within Red Hat!
>
> I don't understand why a carefully written Mantis ticket is not sufficient for
> discussion, but apparently it isn't. :/
>
>
> (c) Case in point, please see Mantis ticket #1736, titled
>
> lacking specification of EFI_BOOT_SCRIPT_WIDTH in PI 1.5 / Vol 5 /
> 8.7.1 Save State Write
>
> which I had originally filed in December 2016.
>
> In February 2017, I was asked for more details. I said, "fair enough", and I
> spent
> half a day writing up the requested change in *full* detail.
> I gave editing instructions of the form
>
> change this to that
>
> and
>
> add/delete the following
>
> as recommended in Mark's email (b).
>
> You can see my write-up in note 0005044. After that note, there have been
> *zero* updates to the ticket; since February 2017.
>
>
> So the fact is, unless you have time to call the WG meetings every week, and
> push *live* for the change that you want, you have no chance at getting stuff
> into the specs.
>
>
> I mean, in his email (b), Mark suggests asking a "proxy" for representing the
> change request, to anyone that cannot dial in. Well, can *you* be my proxy on
> the PIWG meeting, if I write up the change request? You certainly understand
> the problem space, and you maintain the corresponding reference code in edk2.
> I just doubt you have time for conference calls, same as I.
>
> UefiBootManagerLib already reports an extended status code, with
> EDKII_SET_VARIABLE_STATUS payload. Introducing another edk2-specific status
> code requires no slow negotiation, and it can be adopted by others, in
> practice,
> if they like it. Once it is wide-spread practice, it can be more easily
> codified in
> the spec. The specifics for the first implementation can be -- should be --
> discussed on this open list; we had better not standardize something that has
> zero implementations just yet.
>
> Anyway, I'm willing to go through the standardization process, but only if it
> doesn't require me to pick up the phone every week (esp. at midnight).
>
> Thanks
> Laszlo
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