Re: [U-Boot] [RFC PATCH 0/6] ARMv7: Add HYP mode switching support
On Fri, Apr 26, 2013 at 7:14 AM, Andre Przywara wrote: > On 04/26/2013 03:42 PM, Peter Maydell wrote: >> On 26 April 2013 14:24, Andre Przywara wrote: >>> On 04/26/2013 03:18 PM, Peter Maydell wrote: The obvious question here is "why do we need a new command?". The kernel booting specification says "boot the kernel in Hyp mode" so we should just always do that for booting Linux, surely? >> >>> Because it avoids regressions. I kind of feel uneasy to do a lot of >>> tinkering with secure state and the GIC unconditionally, especially if >>> enabled on many boards with virt-capable CPUs. >> >> There aren't exactly very many of those out there, so if we >> default to "boot in HYP mode" then (a) KVM will just work >> out of the box and (b) people doing u-boot ports to their >> board will find any issues and be able to submit fixes. >> If we don't turn it on by default then we'll end up stuck >> in a world where KVM doesn't work on half the virt capable >> boards out there. > > OK, that's a point. I changed the code already and will include it in > the next revision. > I strongly agree with Peter, and in fact I think it should only be a compile time option, not a run-time option, only for those debugging u-boot and a kernel on some new platform. -Christoffer ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [RFC PATCH 0/6] ARMv7: Add HYP mode switching support
On 26 April 2013 14:14, Andre Przywara wrote: > ARM CPUs with the virtualization extension have a new mode called > HYP mode, which allows hypervisors to safely control and monitor > guests. The current hypervisor (KVM and Xen) implementations > require the kernel to be entered in that HYP mode. > > This patch series introduces a new U-Boot command called "hypmode" > which can be used at any time at the U-Boot command prompt to > switch the CPU into HYP mode - ideally this would be done before > starting the kernel. The obvious question here is "why do we need a new command?". The kernel booting specification says "boot the kernel in Hyp mode" so we should just always do that for booting Linux, surely? thanks -- PMM ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [RFC PATCH 0/6] ARMv7: Add HYP mode switching support
On 26 April 2013 14:24, Andre Przywara wrote: > On 04/26/2013 03:18 PM, Peter Maydell wrote: >> The obvious question here is "why do we need a new command?". >> The kernel booting specification says "boot the kernel in >> Hyp mode" so we should just always do that for booting Linux, >> surely? > Because it avoids regressions. I kind of feel uneasy to do a lot of > tinkering with secure state and the GIC unconditionally, especially if > enabled on many boards with virt-capable CPUs. There aren't exactly very many of those out there, so if we default to "boot in HYP mode" then (a) KVM will just work out of the box and (b) people doing u-boot ports to their board will find any issues and be able to submit fixes. If we don't turn it on by default then we'll end up stuck in a world where KVM doesn't work on half the virt capable boards out there. I have no objection to a "turn this off" escape hatch if you think it's useful. -- PMM ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [RFC PATCH 0/6] ARMv7: Add HYP mode switching support
On 04/26/2013 03:42 PM, Peter Maydell wrote: On 26 April 2013 14:24, Andre Przywara wrote: On 04/26/2013 03:18 PM, Peter Maydell wrote: The obvious question here is "why do we need a new command?". The kernel booting specification says "boot the kernel in Hyp mode" so we should just always do that for booting Linux, surely? Because it avoids regressions. I kind of feel uneasy to do a lot of tinkering with secure state and the GIC unconditionally, especially if enabled on many boards with virt-capable CPUs. There aren't exactly very many of those out there, so if we default to "boot in HYP mode" then (a) KVM will just work out of the box and (b) people doing u-boot ports to their board will find any issues and be able to submit fixes. If we don't turn it on by default then we'll end up stuck in a world where KVM doesn't work on half the virt capable boards out there. OK, that's a point. I changed the code already and will include it in the next revision. Thanks, Andre. I have no objection to a "turn this off" escape hatch if you think it's useful. -- PMM ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [RFC PATCH 0/6] ARMv7: Add HYP mode switching support
On 04/26/2013 03:18 PM, Peter Maydell wrote: On 26 April 2013 14:14, Andre Przywara wrote: ARM CPUs with the virtualization extension have a new mode called HYP mode, which allows hypervisors to safely control and monitor guests. The current hypervisor (KVM and Xen) implementations require the kernel to be entered in that HYP mode. This patch series introduces a new U-Boot command called "hypmode" which can be used at any time at the U-Boot command prompt to switch the CPU into HYP mode - ideally this would be done before starting the kernel. The obvious question here is "why do we need a new command?". The kernel booting specification says "boot the kernel in Hyp mode" so we should just always do that for booting Linux, surely? Because it avoids regressions. I kind of feel uneasy to do a lot of tinkering with secure state and the GIC unconditionally, especially if enabled on many boards with virt-capable CPUs. As written in question 2) later in that mail, I can also live with a command to _dis_able the HYP mode switching in case it causes problems. Regards, Andre. ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
[U-Boot] [RFC PATCH 0/6] ARMv7: Add HYP mode switching support
ARM CPUs with the virtualization extension have a new mode called HYP mode, which allows hypervisors to safely control and monitor guests. The current hypervisor (KVM and Xen) implementations require the kernel to be entered in that HYP mode. This patch series introduces a new U-Boot command called "hypmode" which can be used at any time at the U-Boot command prompt to switch the CPU into HYP mode - ideally this would be done before starting the kernel. Since U-Boot does not use the MMU, it runs fine in HYP mode, so you could as well enter HYP mode earlier. The process of switching into HYP mode requires the CPU to be in non-secure state, which requires the GIC to be programmed properly first. Explanations about the details are in the commit messages of the respective patches. The code aims to be as generic as possible, though currently it has only been tested on the Versatile Express TC-2 board. The last patch thus enables the feature for that board and relies on the Versatile Express updates patches sent out lately[1]. I would like to get some feedback on the patches, especially about: 1) Is the code in the right places? I used arch/arm/lib/ and arch/arm/cpu/armv7/ as directories for the ARM code and common/ for the actual command. 2) Is a command to switch to HYP actually the right thing? Should HYP be entered automatically instead? Or provide an option to skip HYP mode if requested by the user? 3) Does it make sense to provide a "nonsec" command also? I cannot name any usecases by now, but the implementation would be rather easy with basically all the functionality already there. In general I appreciate any comments about coding style, patch layout or the actual implementation. Thanks for watching! Andre. [1] http://lists.denx.de/pipermail/u-boot/2013-April/151366.html Andre Przywara (6): ARM: add secure monitor handler to switch to non-secure state ARM: add assembly routine to switch to non-secure state ARM: add U-Boot command "hypmode" to switch to non-secure state ARM: add SMP support for non-secure switch ARM: extend non-secure switch to also go into HYP mode ARM: VExpress: enable ARMv7 virt support for VExpress A15 arch/arm/cpu/armv7/start.S | 116 --- arch/arm/include/asm/armv7.h| 2 + arch/arm/lib/Makefile | 2 + arch/arm/lib/virt-v7.c | 132 common/Makefile | 1 + common/cmd_virt.c | 65 ++ include/configs/vexpress_ca15_tc2.h | 3 + 7 files changed, 311 insertions(+), 10 deletions(-) create mode 100644 arch/arm/lib/virt-v7.c create mode 100644 common/cmd_virt.c -- 1.7.12.1 ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
