On Tue, Oct 07, 2014 at 03:43:16PM -0500, Joel Schopp wrote: > > On 10/07/2014 02:17 PM, Joel Schopp wrote: > > On 10/07/2014 01:34 PM, Christoffer Dall wrote: > >> On Tue, Oct 07, 2014 at 01:28:38PM -0500, Joel Schopp wrote: > >>>>> -drive file=/Image.img,id=fs -device virtio-blk-device,drive=fs > >>>>> > >>>>> more specifically > >>>>> ./aarch64-softmmu/qemu-system-aarch64 -smp 1 --enable-kvm -nographic > >>>>> -kernel /Image -drive file=/Image.img,id=fs -device > >>>>> virtio-blk-device,drive=fs -m 1024 -M virt -cpu host -no-reboot -append > >>>>> "console=ttyAMA0 console=ttyS0 rootwait root=/dev/vda4 rw" > >>>>> > >>>> Can you post your guest kernel config somewhere for me to try and > >>>> reproduce? > >>> Thanks for offering to help. Before you spend some time on it let me > >>> debug and see what progress I can make. Since I can reproduce it > >>> reliably now I can narrow things down with git bisect. > Traced it back to the introduction of NO_HZ. Going from > CONFIG_HZ_PERIODIC to CONFIG_NO_HZ_IDLE or CONFIG_NO_HZ_FULL is enough > to do it. Is this specific to running in a VM or do those options break your host system as well? > > Earlier in boot there was a message that might be related: > drivers/rtc/hctosys.c: unable to open rtc device (rtc0) > And indeed there is not rtc or rtc0 in /dev in the guest like there is > on the host. I'm guessing this is more missing functionality than it is > a bug. > Hmmm, as far as I understand this, the RTC is not related to having CONFIG_NO_HZ_FULL and friends. The RTC is only there to provide you an actual read of wall-clock date/time, where the architected timers should be used in an ARM VM as the clocsource and to program timer interrupts. Tangentially, recent versions of QEMU should have an RTC in the '-M virt' machine, specifically a pl031, so you could try to add CONFIG_RTC_DRV_PL031=y to your guest kernel config and see if the warning above disappears, assuming you have a recent enough version of qemu (use 2.1.0, or check hw/arm/virt.c for VIRT_RTC in the memmap). -Christoffer _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
