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@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@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
On Fri, Nov 23, 2018 at 4:54 PM Kevin O'Connor kevin@koconnor.net wrote:
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@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@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?
Yes, it is not standard. I posted a small patch in this thread (https://mail.coreboot.org/pipermail/seabios/2018-November/012592.html) to explain my experiments. CONFIG_DISABLE_VGA=y simply skips the vgarom_setup() and enable_vga_console().
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.
Thanks, I'll investigate better the delays.
Cheers, Stefano
-Kevin
-
Kevin O'Connor -
Stefano Garzarella