On 10/4/2023 5:50 PM, Steven Rostedt wrote: >> I've copied Steven Rostedt who is the maintainer of tracefs to see if he >> has any comment. I just noticed arch/x86/boot/msr.h and I see that it >> redefines rdmsr() and wrmsr() and omits the tracepoints. A comment there >> explains: >> >> /* >> * The kernel proper already defines rdmsr()/wrmsr(), but they are not for the >> * boot kernel since they rely on tracepoint/exception handling infrastructure >> * that's not available here. >> */ >> >> We could do something similar for inb()/outb() and redefine them in >> arch/x86/boot/io.h instead of including <asm/shared/io.h> there. > > That would be a saner approach. > > -- Steve I tried this but it is problematic because there are include chains that define inb()/outb() without including arch/x86/boot/io.h at all. For example: arch/x86/boot/compressed/misc.c -> arch/x86/boot/compressed/misc.h -> include/linux/acpi.h -> include/acpi/acpi_io.h -> include/linux/io.h -> arch/x86/include/asm/io.h -> arch/x86/include/asm/shared/io.h What we need is to disable tracepoints altogether in arch/x86/boot/* so I added -DDISABLE_TRACEPOINTS to the relevant Makefiles and I added a check for that symbol in tracepoint-defs.h. I will submit a v4 version of my patch with these changes shortly. This resolves the problem with <asm/msr.h> as well. After applying the v4 patch I was able to call rdmsr()/wrmsr() from arch/x86/boot/misc.c. Theoretically we can now remove arch/x86/boot/msr.h but I had trouble with that due to compiler warnings and errors. The include files in arch/x86/boot are a mess. Maybe this can be cleaned up in another patch.
