Re: [Xen-devel] [PATCH] tools/firmware: update OVMF Makefile

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Wed, Jan 9, 2019 at 8:46 AM Anthony PERARD <anthony.perard@xxxxxxxxxx> wrote:
>
> On Wed, Jan 09, 2019 at 07:56:59AM -0700, Tamas K Lengyel wrote:
> > On Wed, Jan 9, 2019 at 7:56 AM Tamas K Lengyel
> > <tamas.k.lengyel@xxxxxxxxx> wrote:
> > >
> > > On Wed, Nov 28, 2018 at 10:44 AM Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> > > >
> > > > OVMF has become dependent on OpenSSL, which it is included as a 
> > > > submodule.
> > > > Initialise submodules before building.
> > >
> > > If you are updating the ovmf makefile, could you by any chance also
> > > make the debug build of it more useful on Xen by making it print to
> > > the Xen console? Needs the -D DEBUG_ON_SERIAL_PORT flag added and the
> > > following one-liner to change it to correct port:
> > >
> > > sed -i 's/PcdDebugIoPort|0xe9/PcdDebugIoPort|0x402/g' OvmfPkg/OvmfPkg.dec
> > >
> >
> > Whops, actually the other way around for sed:
> >
> > sed -i 's/PcdDebugIoPort|0x402/PcdDebugIoPort|0xe9/g' OvmfPkg/OvmfPkg.dec
>
> You can actually have OVMF debug output without rebuilding it, add this
> to our VM config:
> device_model_args_hvm = [
>   # Debug OVMF
>   '-chardev', 
> 'file,id=debugcon,mux=on,path=/var/log/xen/qemu-dm-ovmf.log.debugcon,',
>   '-device', 'isa-debugcon,iobase=0x402,chardev=debugcon',
> ]
>
> That way OVMF boot isn't slow down by writing to an ioport if there
> isn't someone to care.
>
> The way you suggest will have OVMF write to an ioport that the Xen
> hypervisor will then write to it's console (or xl dmesg) and with the
> amount of debug that ovmf write, this is quite slow. And worse, that
> isn't going to work anymore with upstream OVMF as it now check if there
> is something to listen on the other side of the ioport, Xen isn't going
> answer the right things and OVMF will stay silence. (That paragraph is
> about the change of PcdDebugIoPort.)
>
> I don't know if DEBUG_ON_SERIAL_PORT is going to work, and how it works,
> but it certainly don't use PcdDebugIoPort. Using a serial port instead
> of an IO port is even going to be slower. So I don't know if it would be
> useful to have.

Ah, thanks for that info! We should probably put that on the wiki too ;)

Tamas

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