Re: [Qemu-devel] SeaBIOS booting time optimization

[Gerd Hoffmann]

  Hi,

> just an update, I enabled the debug prints and I saw two timeouts fired
> with a lot
> of time lost (~780ms between "init timer" and "Scan for VGA ..."),
> putting other prints I discovered that a lot of time is spent in the
> tpm_setup(),
> during the probe of the 2 TPM devices:
> 
> 00.548869 init timer
> 00.549677 ./src/post.c:157 platform_hardware_setup
> 00.550182 ./src/hw/tpm_drivers.c:579 tpmhw_probe
> 01.300833 WARNING - Timeout at wait_reg8:81!
> 01.301388 ./src/hw/tpm_drivers.c:579 tpmhw_probe
> 01.331843 WARNING - Timeout at wait_reg8:81!
> 01.332316 ./src/post.c:160 platform_hardware_setup
> 01.333358 Scan for VGA option rom
> 
> Indeed, in the probe of the TPM devices (TIS and CRB)  there are timeouts of
> 750 ms and 30 ms respectively.
> 
> Then, statically disabling TPM and TCG (CONFIG_TCGBIOS) the time spent
> in SeaBIOS goes down from ~846ms to ~56ms:
> # SeaBIOS disabling CONFIG_TCGBIOS
> BIOS=/home/stefano/repos/seabios/out_notcgbios/bios.bin
>  qemu_init_end: 40.658371
>  fw_start: 40.850395 (+0.192024)
>  fw_do_boot: 96.750142 (+55.899747)
>  linux_start_boot: 98.880578 (+2.130436)
> 
> The tpm_setup() is called after the qemu_cfg_init(), so I think we can
> disable
> this call using some fw_cfg parameters, if we will decide to implement a
> runtime
> approach.

Another possible option is to simply use shorter timeouts on qemu (using
runningOnQEMU()), I'd suggest to check with the TPM maintainers whenever
that is ok.

Background:  The drivers in seabios work on both virtual and physical
hardware (you can run seabios as coreboot payload on physical hardware).
There are quite a few places where are delays and timeouts which are
required to work properly on physical hardware.  But typically virtual
hardware is alot faster.  There is -- for example -- no time needed to
establish a sata link.  Link detection in ahci is instant on qemu.

cheers,
  Gerd