On Wed, Dec 03, 2014 at 10:18:36PM +0100, Christoffer Dall wrote: > Several people have reported problems with rebooting ARM VMs, especially > on 32-bit ARM. This is mainly due to the same reason we were seeing > boot errors in the past, namely that the ram, dcache, and icache weren't > coherent on guest boot with the guest (stage-1) MMU disabled. We solved > this by ensuring coherency when we fault in pages, but since most memory > is already mapped after a reboot, we don't do anything. > > The solution is to unmap the regular RAM on VCPU init, but we must > take care to not unmap the GIC or other IO regions, hence the somehwat > complicated solution. > > As part of figuring this out, it became clear that some semantics around > the KVM_ARM_VCPU_INIT ABI and system event ABI was unclear (what is > userspace expected to do when it receives a system event). This series > also clarifies the ABI and changes the kernel functionality to do what > userspace expects (turn off VCPUs on a system shutdown event). > > The code is avaliable here as well: > http://git.linaro.org/people/christoffer.dall/linux-kvm-arm.git vcpu_init_fixes-v2 > > There is an alternative version with more code-reuse for the unmapping > implementation for the previous version of this patch series available > in the following git repo: > > http://git.linaro.org/people/christoffer.dall/linux-kvm-arm.git vcpu_init_fixes-alternative > > Testing > ------- > This has been tested on CubieBoard, Arndale, TC2, and Juno. On Arndale > and TC2 it was extremely easy to reproduce the problem (just start a VM > that runs reboot from /etc/rc.local or similar) and this series clearly > fixes the behavior. For the previous version of this series, I was > seeing some problems on Juno, but it turned out to be because I wasn't > limiting my testing to one of the clusters, and since we don't support > re-initing a VCPU on a different physical host CPU (big.LITTLE), it was > failing. For this version of the patch series, it has been running a > reboot loop on Juno for hours. Just tested this version. Looks good. No problems after install nor after many, many reboots. drew > > Changelog > --------- > Changes v1->v2: > - New patch to not clear the VCPU_POWER_OFF flag > - Fixed spelling error in commit message > - Adapted ABI texts based on Peter's feedback > - Check for changed parameters to KVM_ARM_VCPU_INIT > - Now unmap the Stage-2 RAM mappings at VCPU init instead of at PSCI > system event time. > > Christoffer Dall (6): > arm/arm64: KVM: Don't clear the VCPU_POWER_OFF flag > arm/arm64: KVM: Correct KVM_ARM_VCPU_INIT power off option > arm/arm64: KVM: Reset the HCR on each vcpu when resetting the vcpu > arm/arm64: KVM: Clarify KVM_ARM_VCPU_INIT ABI > arm/arm64: KVM: Turn off vcpus on PSCI shutdown/reboot > arm/arm64: KVM: Introduce stage2_unmap_vm > > Documentation/virtual/kvm/api.txt | 17 +++++++++- > arch/arm/include/asm/kvm_emulate.h | 5 +++ > arch/arm/include/asm/kvm_host.h | 2 -- > arch/arm/include/asm/kvm_mmu.h | 1 + > arch/arm/kvm/arm.c | 56 ++++++++++++++++++++++++++++++- > arch/arm/kvm/guest.c | 26 --------------- > arch/arm/kvm/mmu.c | 65 ++++++++++++++++++++++++++++++++++++ > arch/arm/kvm/psci.c | 19 +++++++++++ > arch/arm64/include/asm/kvm_emulate.h | 5 +++ > arch/arm64/include/asm/kvm_host.h | 3 +- > arch/arm64/include/asm/kvm_mmu.h | 1 + > arch/arm64/kvm/guest.c | 26 --------------- > 12 files changed, 168 insertions(+), 58 deletions(-) > > -- > 2.1.2.330.g565301e.dirty > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
