Re: [PATCH v3 0/4] BaseIoFifoLib

["Duran, Leo" <leo.duran@amd.com>]

Jordan, Liming, et al,

It turns out that the runtime enablement of SEV feature that I referred to can be detected in hardware;
so instead of requiring 'driver' code to set a dynamic PCD, the override Fifo routines could do a runtime check like this:

// In override version of the Fifo library
fifo_foo()
{
	If (SEV_Enabled()) {
		// don't use REP ins/outs
	} else {
		// use REP ins/outs
	}
}
In essence we already have a hardware-based dynamic PCD, so the idea is to leverage it.

And since we're interested in overriding just the Fifo routines, it would make better sense to keep them in a separate library (as proposed in the patch set).
Leo.

> -----Original Message-----
> From: Jordan Justen [mailto:jordan.l.justen@intel.com]
> Sent: Friday, January 06, 2017 6:50 PM
> To: Duran, Leo <leo.duran@amd.com>; 'Laszlo Ersek' <lersek@redhat.com>;
> Gao, Liming <liming.gao@intel.com>; edk2-devel@lists.01.org
> Cc: Singh, Brijesh <brijesh.singh@amd.com>; Fan, Jeff <jeff.fan@intel.com>;
> Kinney, Michael D <michael.d.kinney@intel.com>; Ma, Maurice
> <maurice.ma@intel.com>; Agyeman, Prince <prince.agyeman@intel.com>;
> Ni, Ruiyu <ruiyu.ni@intel.com>; Steele, Kelly <kelly.steele@intel.com>; Wei,
> David <david.wei@intel.com>; Guo, Mang <mang.guo@intel.com>
> Subject: RE: [PATCH v3 0/4] BaseIoFifoLib
> 
> On 2017-01-06 07:23:47, Duran, Leo wrote:
> >
> >
> > > -----Original Message-----
> > > From: Laszlo Ersek [mailto:lersek@redhat.com]
> > > Sent: Friday, January 06, 2017 5:12 AM
> > > To: Gao, Liming <liming.gao@intel.com>; Duran, Leo
> > > <leo.duran@amd.com>; edk2-devel@lists.01.org
> > > <edk2-devel@ml01.01.org>
> > > Cc: Singh, Brijesh <brijesh.singh@amd.com>; Justen, Jordan L
> > > <jordan.l.justen@intel.com>; Fan, Jeff <jeff.fan@intel.com>; Kinney,
> > > Michael D <michael.d.kinney@intel.com>; Ma, Maurice
> > > <maurice.ma@intel.com>; Agyeman, Prince
> <prince.agyeman@intel.com>;
> > > Ni, Ruiyu <ruiyu.ni@intel.com>; Steele, Kelly
> > > <kelly.steele@intel.com>; Wei, David <david.wei@intel.com>; Guo,
> > > Mang <mang.guo@intel.com>
> > > Subject: Re: [PATCH v3 0/4] BaseIoFifoLib
> > >
> > > On 01/06/17 07:02, Gao, Liming wrote:
> > > > Leo:
> > > > FifoIo is one width type of EFI_CPU_IO_PROTOCOL_WIDTH. So, how
> > > > about add new APIs into IoLib together with other Io APIs? If so,
> > > > no new library class is required. Platform DSC files are not
> > > > required to be changed.
> > >
> > > But then all of the IoLib instances will have to be extended too:
> > >
> > > IntelFrameworkPkg/Library/DxeIoLibCpuIo/DxeIoLibCpuIo.inf
> > > MdePkg/Library/BaseIoLibIntrinsic/BaseIoLibIntrinsic.inf
> > > MdePkg/Library/DxeIoLibCpuIo2/DxeIoLibCpuIo2.inf
> > > MdePkg/Library/DxeIoLibEsal/DxeIoLibEsal.inf
> > > MdePkg/Library/PeiIoLibCpuIo/PeiIoLibCpuIo.inf
> > > MdePkg/Library/SmmIoLibSmmCpuIo2/SmmIoLibSmmCpuIo2.inf
> > >
> > > Thanks,
> > > Laszlo
> > >
> > [Duran, Leo] Correct.
> > As I mentioned, one of the reasons for the new IoFifo library is to be
> > able to override it without having to duplicate the complete IoLib.
> >
> 
> I agree with Liming about adding the functions to IoLib instead.
> 
> Perhaps a PCD could be added to control if rep i/o instructions are
> used.
> 
> -Jordan