Re: [PATCH v2] xen: arm64: more useful logging on bad trap.

[Ian Campbell <Ian.Campbell@citrix.com>]

On Wed, 2015-02-18 at 17:26 +0000, Andrew Cooper wrote:
> On 18/02/15 17:01, Ian Campbell wrote:
> > Dump the register state before panicing so we have some clue where the
> > issue occurred. Also decode the ESR register a bit to save having to
> > grab a pen and paper.
> >
> > ESR_EL2 is a 32-bit register, so use SYSREG_READ32 not ..._READ64, as
> > we already do correctly in the main trap handler.
> >
> > While here notice that do_trap_serror is never called and remove it.
> >
> > Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> > Reviewed-by: Julien Grall <julien.grall@linaro.org>
> > Tested-by: Jintack Lim <jintack@cs.columbia.edu>
> > Cc: jintack@cs.columbia.edu
> > ---
> > Jintack, since you have a system which is exhibiting SError issues I
> > wonder if I could prevail on you to give this patch a try on your
> > system and report on the output. I've only compile tested this myself.
> >
> > v2: Added blank line after variable declaration
> >     Split log message into two lines.
> >     s/code/ESR/ and reformat a little.
> > ---
> >  xen/arch/arm/arm64/traps.c |   14 ++++++--------
> >  1 file changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/xen/arch/arm/arm64/traps.c b/xen/arch/arm/arm64/traps.c
> > index 1693b5d..31a3ca5 100644
> > --- a/xen/arch/arm/arm64/traps.c
> > +++ b/xen/arch/arm/arm64/traps.c
> > @@ -24,11 +24,6 @@
> >  
> >  #include <public/xen.h>
> >  
> > -asmlinkage void do_trap_serror(struct cpu_user_regs *regs)
> > -{
> > -    panic("Unhandled serror trap");
> > -}
> > -
> >  static const char *handler[]= {
> >          "Synchronous Abort",
> >          "IRQ",
> > @@ -38,11 +33,14 @@ static const char *handler[]= {
> >  
> >  asmlinkage void do_bad_mode(struct cpu_user_regs *regs, int reason)
> >  {
> > -    uint64_t esr = READ_SYSREG64(ESR_EL2);
> > -    printk("Bad mode in %s handler detected, code 0x%08"PRIx64"\n",
> > -           handler[reason], esr);
> > +    union hsr hsr = { .bits = READ_SYSREG32(ESR_EL2) };
> > +
> > +    printk("Bad mode in %s handler detected", handler[reason]);
> > +    printk("ESR=0x%08"PRIx32":  EC=%"PRIx32", IL=%"PRIx32", ISS=%"PRIx32"\n",
> > +           hsr.bits, hsr.ec, hsr.len, hsr.iss);
> 
> This would be better as a single printk() call, otherwise a different
> cpu issuing a printk() could interleave in the middle of the line.
> 
> Also, you appear to have dropped the space between "detected" and "ESR"

That's because I forgot to add the \n to the end of the first printk
(the intention was to make the log line <80 columns by splitting it into
two lines). Having fixed that I think your first comment then becomes
irrelevant? Or is there some benefit to printk("foo\nbar\n")?

Ian.