On 2015-01-27 00:17:52, Laszlo Ersek wrote:
> On 01/26/15 22:32, Jordan Justen wrote:
> > On 2015-01-24 15:04:52, Laszlo Ersek wrote:
> >> +EFI_STATUS
> >> +EFIAPI
> >> +InstallAllQemuLinkedTables (
> >> + IN EFI_ACPI_TABLE_PROTOCOL *AcpiProtocol
> >> + );
> >
> > What do you think about moving this to QemuFwCfgLib instead?
>
> This crossed my mind earlier, but I don't think it's a good idea. Just
> because it depends on FwCfg, I don't want to fuse it with the base
> library. (Same for QemuBootOrderLib.) ("Base" meaning "foundational",
> not "available to all phases", in this context, clearly.)
>
> (1) Main reason is it makes it harder to port the various independent
> features gradually, and/or to port them selectively even for the longer
> term.
>
> A good negative example is the QemuFwCfgS3Enabled() API. Because it was
> so small and so easy to implement for OVMF / x86, we fused it with the
> QemuFwCfgLib interface. When implementing the library class for ARM
> guests, I had no choice but to implement it too (as "return FALSE")
> because it had already been part of the interface. The implementation is
> quite useless, and worse, nothing at all calls it in ArmVirtualizationPkg.
>
> > How about:
> > RETURN_STATUS
> > EFIAPI
> > QemuFwCfgInstallAcpiTables (
> > VOID
> > );
> >
> > Obviously this should just assert if called in SEC or PEI.
>
> I can rename the function if you'd like, but I think build-time (ie.
> interface-level) constraints of an API are superior to runtime asserts.
> This holds for both different UEFI phases and different architectures.
>
> You probably don't like the proliferation of small, QEMU-specific
> libraries in OVMF. I can appreciate that from an aesthetic POV, but
> these features are really this fine-grained, and exposing their
> dependencies on the library class level allows me to port them more
> flexibly.
>
> (2) Another reason is that by making the QemuFwCfgLib lib class more
> comprehensive, code duplication would worsen. The QemuBootOrderLib and
> QemuLoaderLib functionality is identical between ARM and x86. The
> underlying fw_cfg access / transfer methods are different.
They may be different, but looking, I'm wondering why
OvmfPkg/Library/QemuFwCfgLib doesn't have arm support, rather than
putting it into a separate module over in
ArmPlatformPkg/ArmVirtualizationPkg/Library/QemuFwCfgLib.
It still may be valid to discuss whether it make sense to add to the
QemuFwCfgLib interface, but if they are able to be merged into a
single module, then maybe there would be less worry about code
duplication.
To throw out another idea ... If it still feels like there should be a
separation between a library that accesses fw-cfg, and libraries than
make use of fw-cfg data: How about something like QemuFwCfgIoLib and
QemuFwCfgLib?
> If I fused
> these all together, I'd either need two full library instances
> (duplicating QemuBootOrderLib & QemuLoaderLib just for the sake of the
> different fw_cfg access methods), *or* I'd have to keep these all in one
> subdirectory somewhere, and use [Sources.AARCH64] and [Sources.X64,
> Sources.Ia32] sections in the INF file just for the transfer &
> constructor code. I find those sections unwieldy.
Hmm. I guess you already don't like my idea above. :)
-Jordan
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