It is a performance improvement. Steven Rostedt <rost...@goodmis.org> wrote:
>On Fri, 2012-11-16 at 13:57 -0800, Alexander Duyck wrote: >> Instead of using __pa which is meant to be a general function for >converting >> virtual addresses to physical addresses we can use __pa_symbol which >is the >> preferred way of decoding kernel text virtual addresses to physical >addresses. >> >> In this case we are not directly converting C visible symbols however >if we >> know that the instruction pointer is somewhere between _text and >_etext we >> know that we are going to be translating an address form the kernel >text >> space. > >Can I ask what the purpose of this is? I'm a little skeptical of a >change that is just "the preferred way". > >Was there some bug that this fixes? > >-- Steve > >> >> Cc: Steven Rostedt <rost...@goodmis.org> >> Cc: Frederic Weisbecker <fweis...@gmail.com> >> Signed-off-by: Alexander Duyck <alexander.h.du...@intel.com> >> --- >> arch/x86/kernel/ftrace.c | 4 ++-- >> 1 files changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c >> index 1d41402..42a392a 100644 >> --- a/arch/x86/kernel/ftrace.c >> +++ b/arch/x86/kernel/ftrace.c >> @@ -89,7 +89,7 @@ do_ftrace_mod_code(unsigned long ip, const void >*new_code) >> * kernel identity mapping to modify code. >> */ >> if (within(ip, (unsigned long)_text, (unsigned long)_etext)) >> - ip = (unsigned long)__va(__pa(ip)); >> + ip = (unsigned long)__va(__pa_symbol(ip)); >> >> return probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE); >> } >> @@ -279,7 +279,7 @@ static int ftrace_write(unsigned long ip, const >char *val, int size) >> * kernel identity mapping to modify code. >> */ >> if (within(ip, (unsigned long)_text, (unsigned long)_etext)) >> - ip = (unsigned long)__va(__pa(ip)); >> + ip = (unsigned long)__va(__pa_symbol(ip)); >> >> return probe_kernel_write((void *)ip, val, size); >> } -- Sent from my mobile phone. Please excuse brevity and lack of formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
