On Tue, Sep 25, 2012 at 02:48:20PM +0100, Ian Campbell wrote: > On Tue, 2012-09-25 at 00:27 +0100, H. Peter Anvin wrote: > > From: "H. Peter Anvin" <h...@linux.intel.com> > > > > %cr4 is supposed to reflect a set of features into which the operating > > system is opting in. If the BIOS or bootloader leaks bits here, this > > is not desirable. Consider a bootloader passing in %cr4.pae set to a > > legacy paging kernel, for example -- it will not have any immediate > > effect, but the kernel would crash when turning paging on. > > > > A similar argument applies to %eflags, and since we have to look for > > %eflags.id being settable we can use a sequence which clears %eflags > > as a side effect. > > > > Note that we already do this for x86-64. > > > > I would like opinions on this especially from the PV crowd > > Xen PV guests don't pass through this code path so there is no danger > there AFAICT, so from that PoV: > > Acked-by: Ian Campbell <ian.campb...@citrix.com> > > FWIW it looks correct to me from the native PoV too, but you probably > already knew that ;-)
And sanity testing confirmed it. Acked-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> Tested-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> > > Ian. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
