Hi Mario, On 11/02/2015 06:51 PM, Mario Smarduch wrote: > Hello, > 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. > The patch is against 4.2.0-rc2 commit 43297dda0a51 > > Original Description > -------------------- > When booting a VM using QEMU or Kvmtool there are no clear ways to > enable low level debugging for these virtual platforms. some menu port > choices are not supported by the virtual platforms at all. And there is no > help on the location of physical and virtual addresses for the ports. > This may lead to wrong debug port and a frozen VM with a blank screen. > > This patch adds menu selections for QEMU and Kvmtool virtual platforms for low > level kernel print debugging. Help section displays port physical and > virutal addresses. > > ARM reference models use the MIDR register to run-time select UART port address > (for ARCH_VEXPRESS) based on A9 or A15 part numbers. Looked for a same approach > but couldn't find a way to differentiate between virtual platforms, something > like a platform register. > > Acked-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > Signed-off-by: Mario Smarduch <m.smarduch@xxxxxxxxxxx> > --- > arch/arm/Kconfig.debug | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug > index a2e16f9..d126bd4 100644 > --- a/arch/arm/Kconfig.debug > +++ b/arch/arm/Kconfig.debug > @@ -1155,6 +1155,28 @@ choice > This option selects UART0 on VIA/Wondermedia System-on-a-chip > devices, including VT8500, WM8505, WM8650 and WM8850. > > + config DEBUG_VIRT_UART_QEMU > + bool "Kernel low-level debugging on QEMU Virtual Platform" > + depends on ARCH_VIRT > + select DEBUG_UART_PL01X > + help > + Say Y here if you want the debug print routines to direct > + their output to PL011 UART port on QEMU Virtual Platform. > + Appropriate address values are: > + PHYS VIRT > + 0x9000000 0xf8090000 I thought the only guarantee the virt machine had about the memory map was that it would be described in the device tree. > + config DEBUG_VIRT_UART_KVMTOOL > + bool "Kernel low-level debugging on Kvmtool Virtual Platform" > + depends on ARCH_VIRT > + select DEBUG_UART_8250 > + help > + Say Y here if you want the debug print routines to direct > + their output to 8250 UART port on Kvmtool Virtual > + Platform. Appropriate address values are: > + PHYS VIRT > + 0x3f8 0xf80903f8 > + > config DEBUG_ICEDCC > bool "Kernel low-level debugging via EmbeddedICE DCC channel" > help > Regards, 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
