svn commit: r255439 - head/sys/dev/cpuctl

[Konstantin Belousov]

On Tue, Sep 10, 2013 at 07:29:51AM -0700, Matthew Fleming wrote:
> I don't know exactly what the stock malloc(9) will return, but memguard(9),
> under its default mode with vm.memguard.options having MG_GUARD_AROUND set
> will align the returned pointer to only 16 bytes.  When I added that
> feature I almost made it 8 bytes, but I think I saw that uma(9) had a
> 16-byte alignment so I preserved that.  I.e., this code does still work
> with malloc(9) and memguard(9).
> 
> But why does this need 16 byte alignment?  Especially when one of the
> comments says 4-byte alignment?

The comment about 4-byte alignment is for VIA.

For Intel, citing the IA-32 SDM rev. 47, Vol.3, 9.11.6 Microcode Update Loader:
"The microcode update data requires a 16-byte boundary alignment".
I.e. CPU takes the linear address of the buffer, which must be aligned
on 16 bytes.
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