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. > >> > >> Will > >> > > > > 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. -Christoffer -- 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
