Re: [SeaBIOS] About cpu_set, CPU hotplug and related subjects
On 28.04.2010 12:45, Gleb Natapov wrote: On Wed, Apr 28, 2010 at 12:41:51PM +0200, Jes Sorensen wrote: The CPU declarations are particularly tricky as they get pretty big and complex and need to live in the DSDT, whereas a lot of other things we can shift off to separate SSDT tables and only put the minimum that needs to be generated dynamically in it's own table. We can generate complex code statically and call it from dynamically generated CPU declarations. There is some ACPI code generator in coreboot. Not sure if it is usable for those purposes. coreboot uses it to generate AMD CPU frequency tables. Regards, Carl-Daniel -- http://www.hailfinger.org/ -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [SeaBIOS] About cpu_set, CPU hotplug and related subjects
On 04/22/10 03:12, Kevin O'Connor wrote: As I understand it, the hotplug support was only in the kvm copy of bochs bios. It also limited the number of cpus one could use (I think 16). The current smp support in SeaBIOS doesn't limit the number of cpus. So, there has been reluctance to just port the old kvm bios code forward. I believe the number was limited to 15, due to limits in a certain proprietary operating system. The issue with the AML code in BOCHS vs the code in Seabios is a bit tricky. The tables in BOCHS are a fair bit more complicated with the hotplug code and therefore statically generated, whereas Seabios generates them dynamically at boot time. Generating the more complex tables dynamically would be preferred, but it requires like half an AML compiler in Seabios, so it kinda stalled there Cheers, Jes -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [SeaBIOS] About cpu_set, CPU hotplug and related subjects
On Wed, Apr 28, 2010 at 11:31:00AM +0200, Jes Sorensen wrote: On 04/22/10 03:12, Kevin O'Connor wrote: As I understand it, the hotplug support was only in the kvm copy of bochs bios. It also limited the number of cpus one could use (I think 16). The current smp support in SeaBIOS doesn't limit the number of cpus. So, there has been reluctance to just port the old kvm bios code forward. I believe the number was limited to 15, due to limits in a certain proprietary operating system. The issue with the AML code in BOCHS vs the code in Seabios is a bit tricky. The tables in BOCHS are a fair bit more complicated with the hotplug code and therefore statically generated, whereas Seabios generates them dynamically at boot time. Generating the more complex tables dynamically would be preferred, but it requires like half an AML compiler in Seabios, so it kinda stalled there We can try to be smart and generate most of the code statically and only minimum that absolutely required dynamically. Haven't looked at how simple dynamic part can be made. -- Gleb. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [SeaBIOS] About cpu_set, CPU hotplug and related subjects
On 04/28/10 12:30, Gleb Natapov wrote: On Wed, Apr 28, 2010 at 11:31:00AM +0200, Jes Sorensen wrote: On 04/22/10 03:12, Kevin O'Connor wrote: Generating the more complex tables dynamically would be preferred, but it requires like half an AML compiler in Seabios, so it kinda stalled there We can try to be smart and generate most of the code statically and only minimum that absolutely required dynamically. Haven't looked at how simple dynamic part can be made. I looked at it briefly and ran away screaming :) I am sure it can be done, bit it would require pretty good understanding of the AML encodings. The CPU declarations are particularly tricky as they get pretty big and complex and need to live in the DSDT, whereas a lot of other things we can shift off to separate SSDT tables and only put the minimum that needs to be generated dynamically in it's own table. Cheers, Jes -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [SeaBIOS] About cpu_set, CPU hotplug and related subjects
On Wed, Apr 28, 2010 at 12:41:51PM +0200, Jes Sorensen wrote: On 04/28/10 12:30, Gleb Natapov wrote: On Wed, Apr 28, 2010 at 11:31:00AM +0200, Jes Sorensen wrote: On 04/22/10 03:12, Kevin O'Connor wrote: Generating the more complex tables dynamically would be preferred, but it requires like half an AML compiler in Seabios, so it kinda stalled there We can try to be smart and generate most of the code statically and only minimum that absolutely required dynamically. Haven't looked at how simple dynamic part can be made. I looked at it briefly and ran away screaming :) I am sure it can be This is normal reaction to ACPI of a healthy human being. done, bit it would require pretty good understanding of the AML encodings. The CPU declarations are particularly tricky as they get pretty big and complex and need to live in the DSDT, whereas a lot of other things we can shift off to separate SSDT tables and only put the minimum that needs to be generated dynamically in it's own table. We can generate complex code statically and call it from dynamically generated CPU declarations. -- Gleb. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: About cpu_set, CPU hotplug and related subjects
On Mon, Apr 19, 2010 at 04:34:54PM -0300, Lucas Meneghel Rodrigues wrote: After doing some reading it seems to me that the reason why that is not happening is because SeaBIOS still doesn't have code to support CPU hot plugging as BochsBIOS did. As I understand it, the hotplug support was only in the kvm copy of bochs bios. It also limited the number of cpus one could use (I think 16). The current smp support in SeaBIOS doesn't limit the number of cpus. So, there has been reluctance to just port the old kvm bios code forward. -Kevin -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
About cpu_set, CPU hotplug and related subjects
Hi folks, I've implemented a functional test for the cpu_set feature some time ago. I was going through the patch queue and realized the patch needed some respin, so I did it. I decided to try and see what is the state of the feature, considering last time I tried it was not working (segfaulting). Now, with the latest qemu-kvm things are on a much better shape, cpu_set is not giving me segfaults, and qemu monitor reports the new cpus added. 10:21:20 INFO | Adding 1 CPUs to guest 10:21:20 DEBUG| Sending monitor command: cpu_set 0 online 10:21:20 DEBUG| Sending monitor command: cpu_set 1 online 10:21:20 DEBUG| Sending monitor command: info cpus 10:21:20 DEBUG| Output of info cpus: * CPU #0: pc=0x8102e23d thread_id=11035 CPU #1: pc=0x thread_id=11065 The address of the CPU #1 seems a little strange. The guest OS is completely unaware of any changes to the number of CPUs though. After doing some reading it seems to me that the reason why that is not happening is because SeaBIOS still doesn't have code to support CPU hot plugging as BochsBIOS did. I also looked after some documentation about how that feature is supposed to work, and didn't find it. So, assuming my understanding about the current status is correct: 1) Is anybody planning on adding the necessary support to SeaBIOS anytime soon? 2) How the whole functionality is supposed to work? My mental model goes like this: * cpu_set [total number of CPUs you want the system to have] online * Guest should notice new CPUS added to the system and they appear under /sys/devices/system/cpu/cpu*, initially offlined * The online status of each CPU is in /sys/devices/system/cpu/cpu*/online, and onlining it is just a matter of writing 1 to this file * It is not possible to downgrade the number of CPUs of the system during the lifetime of the VM process Thanks for your attention, Lucas -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
