Messages in this thread | | | Date | Wed, 7 Feb 2018 12:17:39 +0100 | From | Borislav Petkov <> | Subject | Re: [RFC PATCH 3/4] x86/speculation: Use IBRS if available before calling into firmware |
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Just some random thoughts:
On Wed, Feb 07, 2018 at 12:03:13AM +0000, David Woodhouse wrote: > +#define alternative_msr_write(_msr, _val, _feature) \ > + asm volatile(ALTERNATIVE("", \ > + "movl %[msr], %%ecx\n\t" \ > + "movl %[val], %%eax\n\t" \ > + "movl $0, %%edx\n\t" \
We'll never write anything except 0 in %edx?
> + "wrmsr", \ > + _feature) \ > + : : [msr] "i" (_msr), [val] "i" (_val) \ > + : "eax", "ecx", "edx", "memory")
So I'm not crazy about making it a separate macro because TBH it doesn't look too generic to do that but then again what do I know, considering recent history. :-)
[ Maybe I need to not look at the spectral meltdown for a couple of weeks and simply take a break. ]
I guess it is fine if it is in nospec-branch.h and not prefix it with alternative_ so that it doesn't give people ideas.
Oh and firmware_restrict_branch_speculation_start/end() is just too long a name.
All IMHO, of course.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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