On 11/3/2015 8:33 AM, Christopher Covington wrote: > 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. 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? > >> 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 > -- 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
