On 11/04/2015 08:31 AM, Christoffer Dall wrote: > On Tue, Nov 03, 2015 at 01:39:44PM -0600, Rob Herring wrote: >> On Tue, Nov 3, 2015 at 1:17 PM, Mario Smarduch <m.smarduch@xxxxxxxxxxx> wrote: >>> On 11/3/2015 9:55 AM, Will Deacon wrote: >>>> On Tue, Nov 03, 2015 at 09:44:52AM -0800, Mario Smarduch wrote: >>>>> On 11/3/2015 8:33 AM, Christopher Covington wrote: >>>>>> On 11/02/2015 06:51 PM, Mario Smarduch wrote: >>>>>>> this is a re-post from couple weeks ago, please take time to review this >>>>>>> simple patch which simplifies DEBUG_LL and prevents kernel crash on virtual >>>>>>> platforms. >>>>>>> >>>>>>> Before this patch DEBUG_LL for 'dummy virtual machine': >>>>>>> >>>>>>> ( ) Kernel low-level debugging via EmbeddedICE DCC channel >>>>>>> ( ) Kernel low-level debug output via semihosting I/O >>>>>>> ( ) Kernel low-level debugging via 8250 UART >>>>>>> ( ) Kernel low-level debugging via ARM Ltd PL01x Primecell >>>>>>> >>>>>>> In summary if debug uart is not emulated kernel crashes. >>>>>>> And once you pass that hurdle, uart physical/virtual addresses are unknown. >>>>>>> DEBUG_LL comes in handy on many occasions and should be somewhat >>>>>>> intuitive to use like it is for physical platforms. For virtual platforms >>>>>>> user may start daubting the host and get into a bigger mess. >>>>>>> >>>>>>> After this patch is applied user gets: >>>>>>> >>>>>>> (X) Kernel low-level debugging on QEMU Virtual Platform >>>>>>> ( ) Kernel low-level debugging on Kvmtool Virtual Platform >>>>>>> ..... above repeated .... >>>>>>> >>>>>>> The virtual addresses selected follow arm reference models, high in vmalloc >>>>>>> section with high mem enabled and guest running with >= 1GB of memory. The >>>>>>> offset is leftover from arm reference models. >>>>>> >>>>>> Which model? It doesn't appear to match the vexpress AEM/RTSM/FVP/whatever >>>>>> which used 0x1c090000 for UART0. >>>>> >>>>> I recall QEMU virt model had it's own physical address map, for sure I saw the >>>>> virtio-mmio regions assigned in some ARM document. Peter would you know? >>>>> >>>>> As far as kvmtool I'm not sure, currently PC1 COM1 port is used? Andre will that >>>>> stay fixed? >>>> >>>> We make absolutely no guarantees about the memory map provided by kvmtool. >>> >>> If that's also the case for qemu, then I guess the best you can do is find a way >>> to dump the device tree. Find the uart, physical address and try figure out the >>> virtual address. >>> >>> Pretty involved, hoped for something more automated since that's a handy feature. >> >> You really only need LL_DEBUG now if you are debugging very early code >> before memory is setup and/or bad memory. Use earlycon instead which >> should already be supported both via the pl011 or semihosting. I used >> it with QEMU semihosting support. >> > Then we should really document how to use that with qemu's virt platform > and kvmtool's platform on both 32-bit and 64-bit so that users can > easily figure out what they're doing wrong when they get no output. > > In practice, the address for the pl011 is quite unlikely to change, I > dare speculate, so that documentation shouldn't need frequent updating. Is it not on by default since the following change? http://git.qemu.org/?p=qemu.git;a=commitdiff;h=f022b8e95379b0433d13509706b66f38fc15dde8 Christopher Covington -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project -- 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
