[SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
sgarzare at redhat.com
Tue Nov 20 10:45:31 CET 2018
On Tue, Nov 20, 2018 at 7:21 AM Gerd Hoffmann <kraxel at redhat.com> wrote:
> > 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.
Yes, it is a good idea!
> 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.
I'll investigate also other timeouts.
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