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Re: [SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
by Kevin O'Connor 24 Nov '18

24 Nov '18

On Fri, Nov 23, 2018 at 12:18:13PM +0100, Stefano Garzarella wrote: > On Fri, Nov 23, 2018 at 7:21 AM Gerd Hoffmann <kraxel(a)redhat.com> wrote: > > On Thu, Nov 22, 2018 at 04:13:38PM +0100, Stefano Garzarella wrote: > > > On Thu, Nov 22, 2018 at 12:51 PM Gerd Hoffmann <kraxel(a)redhat.com> wrote: > > > > On Thu, Nov 22, 2018 at 12:08:55PM +0100, Stefano Garzarella wrote: > > > > > Hi, > > > > > I continued to investigate how to reduce the boot time with SeaBIOS > > > > > and QEMU when it used with linuxboot_dma.bin (-kernel parameter). > > > > > I reached ~12ms with a SeaBIOS configuration (attached) where I > > > > > disabled debug output, all Hardware support (except SMM & MTRRs) and I > > > > > applied a small patch to disable VGA setup and console (attached). > > > > > > > > Is there any difference to "qemu -vga none" ? > > > > > > Using both (qemu -vga none, and my patch) we are around 10.8 ms. > > > Note: using only the patch, Linux is still able to initialize and use the VGA. > > > > But do you want linux use the vga console if you care about boot times? > > I'd expect virtio-console would be fastest in that case. > > I agree with you, but if we will implement a QEMU fastboot feature in > SeaBIOS, we are sure that it works with Linux kernel if someone uses > "qemu -kernel" and wants also use a VGA. It should be possible to use "-device VGA,romfile=" to enable VGA without an optionrom. > > > - QEMU -vga none + SeaBIOS config (CONFIG_DEBUG_LEVEL=0, disable all > > > HW support except > > > SMM & MTRRs) + Stephen's TPM patch > > > qemu_init_end: 43.675803 > > > fw_start: 43.865178 (+0.189375) > > > fw_do_boot: 58.093161 (+14.227983) > > > linux_start_boot: 59.490308 (+1.397147) > > > linux_start_user: 556.782354 (+497.292046) > > > > > > - QEMU -vga none + SeaBIOS config (CONFIG_DEBUG_LEVEL=0, disable all > > > HW support except > > > SMM & MTRRs, CONFIG_DISABLE_VGA=y) + Stephen's TPM patch > > > qemu_init_end: 42.387412 > > > fw_start: 42.579257 (+0.191845) > > > fw_do_boot: 53.381517 (+10.802260) > > > linux_start_boot: 54.848643 (+1.467126) > > > linux_start_user: 498.517050 (+443.668407) > > > > Interesting that CONFIG_DISABLE_VGA=y makes a noticable difference even > > without vga hardware being preset. And not only in seabios but also for > > the linux kernel. > > > > Do you know why? > > In SeaBIOS I think the reasons are: > - vgarom_setup() scan all PCI devices to find a VGA > - enable_vga_console() invokes an int10 without check if there is a > VGA (maybe here we can add a check) Where is CONFIG_DISABLE_VGA set - it's not a standard SeaBIOS config option? In my experience, the only meaningful delays are the result of accessing hardware. Neither of the above two items would result in additional hardware accesses, so I don't think they would be the cause of an additional delay. -Kevin

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Re: [SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
by Gerd Hoffmann 23 Nov '18

23 Nov '18

On Thu, Nov 22, 2018 at 04:13:38PM +0100, Stefano Garzarella wrote: > On Thu, Nov 22, 2018 at 12:51 PM Gerd Hoffmann <kraxel(a)redhat.com> wrote: > > > > On Thu, Nov 22, 2018 at 12:08:55PM +0100, Stefano Garzarella wrote: > > > Hi, > > > I continued to investigate how to reduce the boot time with SeaBIOS > > > and QEMU when it used with linuxboot_dma.bin (-kernel parameter). > > > I reached ~12ms with a SeaBIOS configuration (attached) where I > > > disabled debug output, all Hardware support (except SMM & MTRRs) and I > > > applied a small patch to disable VGA setup and console (attached). > > > > Is there any difference to "qemu -vga none" ? > > Using both (qemu -vga none, and my patch) we are around 10.8 ms. > Note: using only the patch, Linux is still able to initialize and use the VGA. But do you want linux use the vga console if you care about boot times? I'd expect virtio-console would be fastest in that case. > - QEMU -vga none + SeaBIOS config (CONFIG_DEBUG_LEVEL=0, disable all > HW support except > SMM & MTRRs) + Stephen's TPM patch > qemu_init_end: 43.675803 > fw_start: 43.865178 (+0.189375) > fw_do_boot: 58.093161 (+14.227983) > linux_start_boot: 59.490308 (+1.397147) > linux_start_user: 556.782354 (+497.292046) > > - QEMU -vga none + SeaBIOS config (CONFIG_DEBUG_LEVEL=0, disable all > HW support except > SMM & MTRRs, CONFIG_DISABLE_VGA=y) + Stephen's TPM patch > qemu_init_end: 42.387412 > fw_start: 42.579257 (+0.191845) > fw_do_boot: 53.381517 (+10.802260) > linux_start_boot: 54.848643 (+1.467126) > linux_start_user: 498.517050 (+443.668407) Interesting that CONFIG_DISABLE_VGA=y makes a noticable difference even without vga hardware being preset. And not only in seabios but also for the linux kernel. Do you know why? cheers, Gerd

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Enable vga_console later during startup
by Julian Sparber 23 Nov '18

23 Nov '18

Hi to all, During boot Seabios shows some text including the version number on top of the screen for a couple of seconds before switching to the boot splash. It doesn't happen every time, but it is really annoying when it does because it makes the boot much less fluid. I fixed this by enabling the vga_console later during the startup. I attached a patch to this email. I tried it in qemu and on my laptop. Let me know what you think. Cheers, jsparber

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Re: [SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
by Gerd Hoffmann 23 Nov '18

23 Nov '18

On Thu, Nov 22, 2018 at 12:08:55PM +0100, Stefano Garzarella wrote: > Hi, > I continued to investigate how to reduce the boot time with SeaBIOS > and QEMU when it used with linuxboot_dma.bin (-kernel parameter). > I reached ~12ms with a SeaBIOS configuration (attached) where I > disabled debug output, all Hardware support (except SMM & MTRRs) and I > applied a small patch to disable VGA setup and console (attached). Is there any difference to "qemu -vga none" ? > Samuel, I put also the total time to userspace (linux_start_user) > adding a probe in the kernel_init() and when I disabled the VGA in the > SeaBIOS I noticed also a speed up in the kernel boot phase. Might come from linux 16bit boot code scanning vgabios for available video modes (for vga=<mode> cmdline arg). > Another approach that I tried, obtaining similar results, is to > recognize the linuxboot_dma.bin at runtime, then skip > device_hardware_setup(), enable_vga_console(), and vgarom_setup(). Hmm, tricky. linuxboot_dma.bin just registers a boot entry, so with "qemu -kernel -boot menu=on" you can still get a boot menu, and the direkt kernel boot is one menu item there. So you can't know for sure whenever a direct kernel boot will happen or not. So, I think at minimum we should make this depend on both linuxboot_dma and boot menu disabled. cheers, Gerd

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Re: [SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
by Gerd Hoffmann 22 Nov '18

22 Nov '18

Hi, > > 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. I'd focus on legacy lpc/isa hardware here. PCI-ish hardware which has such timeouts (sata, usb, ...) typically isn't present in the virtual machine if you care about performance. Or, in other words, the best way to handle the sata link detection delay is to use "qemu -M q35,sata=off". cheers, Gerd

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Re: [SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
by Kevin O'Connor 21 Nov '18

21 Nov '18

On Mon, Nov 19, 2018 at 07:38:39PM +0100, Stefano Garzarella 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 FYI, this was raised a few months ago - see: https://mail.coreboot.org/pipermail/seabios/2018-March/012186.html IIRC, it should be possible to verify the TPM device is present before trying to wait for it. -Kevin

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Re: [SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
by Gerd Hoffmann 20 Nov '18

20 Nov '18

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

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Re: [SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
by Stefan Hajnoczi 20 Nov '18

20 Nov '18

On Mon, Nov 19, 2018 at 11:42:28AM +0100, Stefano Garzarella wrote: > On Mon, Nov 19, 2018 at 9:49 AM Gerd Hoffmann <kraxel(a)redhat.com> wrote: > > > Hi, > > > > > I'm investigating the SeaBIOS booting time, to understand if we can > > > reduce the boot time in some cases (e.g. legacy hardware is not > > > needed). I think this can be interesting also for NEMU developers. > > > > > The goal is to have only one image of SeaBIOS configurable at runtime > > > to reduce the boot time, avoiding unnecessary initialization. > > > > Why at runtime? What is bad with two images? With a runtime option > > you probably need some way to enable the "fastboot" hint for seabios, > > because some optimizations (like skipping ps/2 initialization) breaks > > functionality. So it must be opt-in so you can enable it if you know > > your use case is fine with that. But "qemu -boot fast=on" isn't much > > different from "qemu -bios seabios-fastboot.bin" after all ... > > > > You are right, but maybe having a single image can be simpler to distribute, > and we can implement something (eg. using fw_cfg) to selectively enable > features needed. > Anyway, as the first step, I'll try to build a separate image of SeaBIOS. Gerd, you may be right that explicit an command-line option like -boot fast=on is required. I was hoping SeaBIOS improvements could automatically detect cases where no functionality is lost and would not require new command-line options for users or management tools (e.g. libvirt). For example, if SeaBIOS sees -kernel, is it necessary to follow the full BIOS boot process including loading option ROMs? This way we could avoid scanning PCI devices. Admittedly I don't know the answer to how transparent we can make this, but I hope Stefano will identify how far we can go. Stefan

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Re: [SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization
by Gerd Hoffmann 19 Nov '18

19 Nov '18

Hi, > I'm investigating the SeaBIOS booting time, to understand if we can > reduce the boot time in some cases (e.g. legacy hardware is not > needed). I think this can be interesting also for NEMU developers. > The goal is to have only one image of SeaBIOS configurable at runtime > to reduce the boot time, avoiding unnecessary initialization. Why at runtime? What is bad with two images? With a runtime option you probably need some way to enable the "fastboot" hint for seabios, because some optimizations (like skipping ps/2 initialization) breaks functionality. So it must be opt-in so you can enable it if you know your use case is fine with that. But "qemu -boot fast=on" isn't much different from "qemu -bios seabios-fastboot.bin" after all ... > Any pointers or suggestions would be helpful. seabios could try to skip initializing hardware without bootindex with "qemu -boot menu=off,strict=on". mmconfig support? I think that would reduce the number of vmexits needed for pci initialization. cheers, Gerd

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Re: [SeaBIOS] SeaBIOS booting time optimization
by Samuel Ortiz 19 Nov '18

19 Nov '18

Hi Stefano, On Fri, Nov 16, 2018 at 05:13:59PM +0100, Stefano Garzarella wrote: > Hi, > I'm investigating the SeaBIOS booting time, to understand if we can reduce > the boot time in some cases (e.g. legacy hardware is not needed). I think > this > can be interesting also for NEMU developers. Definitely, thanks. > Following this thread ( > https://mail.coreboot.org/pipermail/seabios/2015-July/009497.html), > I'm using qboot (https://github.com/bonzini/qboot) to compare the SeaBIOS > booting time. > > As Paolo did in qboot, I manually add small debug port writes in SeaBIOS and > linuxboot_dma.c (QEMU) to trace the events with perf (kvm_pio events) When doing similar measuremnts, I also used the debug-exit qemu device in order to make imho simpler measuremnts, see https://github.com/intel/nemu/wiki/Measuring-Boot-Latency Probably not as precised as yours, but it was enough for what we tried to characterize. > The goal is to have only one image of SeaBIOS configurable at runtime to > reduce > the boot time, avoiding unnecessary initialization. > > Any pointers or suggestions would be helpful. > > Following I put some preliminary measurements that I obtained: > I used this QEMU command line: > ./qemu-system-x86_64 -bios $BIOS -m 1G -cpu host -M accel=kvm \ > -kernel /boot/vmlinuz-4.18.18-300.fc29.x86_64 -append 'console=ttyS0' \ > -nographic -serial mon:stdio > > For each test, I measured these times (in milliseconds) relative to the > "sched_process_exec" event: > - qemu_init_end: first kvm_entry (i.e. QEMU initialized has finished) > - fw_start: first entry of the BIOS > - fw_do_boot: after the BIOS initialization (e.g. PCI setup, etc.) > - linux_start_boot: before the jump to the Linux kernel Are you planning to also measure the total time to userspace as well? How we set the hardware up from the FW/BIOS can also influence the overall (up to ring 3) boot latency on our experiments. > # qboot > BIOS=/home/stefano/repos/qboot/bios.bin > qemu_init_end: 40.561234 > fw_start: 40.721729 (+0.160495) > fw_do_boot: 47.025591 (+6.303862) > linux_start_boot: 48.874112 (+1.848521) > > # SeaBIOS with default configuration > BIOS=/home/stefano/repos/seabios/out_default/bios.bin > qemu_init_end: 40.419451 > fw_start: 40.639967 (+0.220516) > fw_do_boot: 886.668828 (+846.028861) > linux_start_boot: 889.723547 (+3.054719) > > # SeaBIOS with Kevin's configuration > # (https://mail.coreboot.org/pipermail/seabios/2015-July/009508.html) > # Note: this SeaBIOS setup is so stripped down that it can't actually boot > an OS > BIOS=/home/stefano/repos/seabios/out_kevin/bios.bin > qemu_init_end: 40.676412 > fw_start: 40.755757 (+0.079345) > fw_do_boot: 56.427023 (+15.671266) That's a slight improvement ;) > I did the same tests also with NEMU (without using -M virt) and I have > approximately the same results. Yes, as expected. > As the next step, I'll start from Kevin's configuration to have a minimal > SeaBIOS image ables to boot a Linux kernel. Please keep us posted. Cheers, Samuel.

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