Re: [Xen-devel] [PATCH v2 1/2] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on_oops

[Ingo Molnar <mingo@xxxxxxxxxx>]

* Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> > These could still be open coded in an inlined fashion, like the scheduler 
> > usage.
> 
> We could have a raw_rdmsr for those.
> 
> OTOH, I'm still not 100% convinced that this warn-but-don't-die behavior is 
> worth the effort.  This isn't a frequent source of bugs to my knowledge, and 
> we 
> don't try to recover from incorrect cr writes, out-of-bounds MMIO, etc, so do 
> we 
> really gain much by rigging a recovery mechanism for rdmsr and wrmsr failures 
> for code that doesn't use the _safe variants?

It's just the general principle really: don't crash the kernel on bootup. 
There's 
few things more user hostile than that.

Also, this would maintain the status quo: since we now (accidentally) don't 
crash 
the kernel on distro kernels (but silently and unsafely ignore the faulting 
instruction), we should not regress that behavior (by adding the chance to 
crash 
again), but improve upon it.

Thanks,

        Ingo

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