On Thu, 2007-03-22 at 09:30 +0200, Avi Kivity wrote:
> Rusty Russell wrote:
> > +static inline unsigned long long native_read_msr(unsigned int msr, int
> > *err)
> > +{
> > + unsigned long long val;
> > +
> > + asm volatile("2: rdmsr ; xorl %0,%0\n"
> > + "1:\n\t"
> > + ".section .fixup,\"ax\"\n\t"
> > + "3: movl %3,%0 ; jmp 1b\n\t"
> > + ".previous\n\t"
> > + ".section __ex_table,\"a\"\n"
> > + " .align 4\n\t"
> > + " .long 2b,3b\n\t"
> > + ".previous"
> > + : "=r" (*err), "=A" (val)
> > + : "c" (msr), "i" (-EFAULT));
> > +
> > + return val;
> > +}
> >
>
>
> > +#define rdmsr(msr,val1,val2)
> > \
> > + do { \
> > + int __err; \
> > + unsigned long long __val = native_read_msr(msr, &__err);
> > \
> > + val1 = __val; \
> > + val2 = __val >> 32; \
> > + } while(0)
> > +
> >
>
> You're silently changing the behavior (as well as the prototype) here,
> rdmsr() used to fail loudly, now it fails silently, with no way for the
> caller to check.
Hi Avi!
Not sure what you're saying about the prototype: the old macro was:
-#define rdmsr(msr,val1,val2) \
- __asm__ __volatile__("rdmsr" \
- : "=a" (val1), "=d" (val2) \
- : "c" (msr))
-
Which doesn't seem to be a great difference to me.
The behaviour change (don't oops when an invalid rdmsr is used) was
there with CONFIG_PARAVIRT=y, the cleanup just made !CONFIG_PARAVIRT the
same. Is it important?
Thanks,
Rusty.
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