[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RFC 02/31] tools/libxc: Use public/featureset.h for cpuid policy generation
On Tue, 2016-01-05 at 15:42 +0000, Andrew Cooper wrote: > On 05/01/16 15:02, Ian Campbell wrote: > > On Tue, 2016-01-05 at 14:23 +0000, Andrew Cooper wrote: > > > On 05/01/16 14:18, Ian Campbell wrote: > > > > On Tue, 2016-01-05 at 14:17 +0000, Andrew Cooper wrote: > > > > > On 05/01/16 14:13, Ian Campbell wrote: > > > > > > On Tue, 2015-12-22 at 09:29 -0700, Jan Beulich wrote: > > > > > > > > > > On 16.12.15 at 22:24, <andrew.cooper3@xxxxxxxxxx> > > > > > > > > > > wrote: > > > > > > > > --- a/xen/include/public/arch-x86/featureset.h > > > > > > > > +++ b/xen/include/public/arch-x86/featureset.h > > > > > > > > @@ -163,6 +163,7 @@ > > > > > > > > Â > > > > > > > > Â/* Intel-defined CPU features, CPUID level > > > > > > > > 0x00000007:0.ebx, > > > > > > > > word > > > > > > > > 5 */ > > > > > > > > Â#define X86_FEATURE_FSGSBASEÂÂÂÂÂÂ( 5*32+ 0) /* > > > > > > > > {RD,WR}{FS,GS}BASE > > > > > > > > instructions */ > > > > > > > > +#define X86_FEATURE_TSC_ADJUSTÂÂÂÂ( 5*32+ 1) /* TSC_ADJUST > > > > > > > > MSR > > > > > > > > available */ > > > > > > > This would probably better go into patch 1. > > > > > > Tools would then see this defined twice with only patch 1 > > > > > > applied, > > > > > > and > > > > > > since the value is actually different I think the compiler will > > > > > > complain. > > > > > > > > > > > > -#define X86_FEATURE_TSC_ADJUSTÂÂÂ1 /* Tsc thread offset */ > > > > > > +#define X86_FEATURE_TSC_ADJUSTÂÂÂÂ( 5*32+ 1) /* TSC_ADJUST MSR > > > > > > available */ > > > > > > > > > > > > The comment change seems to be a semantic one? Or was it wrong > > > > > > beofre? > > > > > Changing patch 1 won't affect the compilation of libxc.ÂÂObserve > > > > > in > > > > > the > > > > > penultimate hunk that I also change the #include > > > > Ah yes. > > > > > > > > What about my comment on the comment changing? > > > Ah yes - the changes are just semantic.ÂÂAlso observe that the same > > > hunk > > > also modifies the libxc macros to modulo 32. > > I'm not talking about the value at all, since I realised that the > > masking > > makes the values the same. I'm talking about the /* comment */ next to > > it > > which has also changed. > > > > > In the end, both the hypervisor and libxc are dealing with > > > hardware-specified bits in registers.ÂÂThis patch is no resulting > > > change > > > to behaviour. > > But do "Tsc thread offset" and "TSC_ADJUST MSR available" mean the same > > thing? Or was "Tsc thread offset" previously actively wrong or > > misleading > > in some way? > > The latter is the accurate meaning of the bit in cpuid.ÂÂThe former is > misleading IMO, and covers one use for it in a Linux world. Thanks, I just wanted to be sure it was an intentional change and not e.g. a cut-and-paste mistake. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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