On Tue, Sep 24, 2019 at 05:28:48PM +0200, Borislav Petkov wrote: > On Tue, Sep 03, 2019 at 05:26:32PM +0300, Jarkko Sakkinen wrote: > > diff --git a/arch/x86/include/asm/cpufeatures.h > > b/arch/x86/include/asm/cpufeatures.h > > index 998c2cc08363..c5582e766121 100644 > > --- a/arch/x86/include/asm/cpufeatures.h > > +++ b/arch/x86/include/asm/cpufeatures.h > > @@ -222,12 +222,22 @@ > > #define X86_FEATURE_L1TF_PTEINV ( 7*32+29) /* "" L1TF > > workaround PTE inversion */ > > #define X86_FEATURE_IBRS_ENHANCED ( 7*32+30) /* Enhanced IBRS */ > > > > -/* Virtualization flags: Linux defined, word 8 */ > > -#define X86_FEATURE_TPR_SHADOW ( 8*32+ 0) /* Intel TPR Shadow > > */ > > -#define X86_FEATURE_VNMI ( 8*32+ 1) /* Intel Virtual NMI */ > > -#define X86_FEATURE_FLEXPRIORITY ( 8*32+ 2) /* Intel FlexPriority */ > > -#define X86_FEATURE_EPT ( 8*32+ 3) /* Intel Extended > > Page Table */ > > -#define X86_FEATURE_VPID ( 8*32+ 4) /* Intel Virtual Processor > > ID */ > > +/* > > + * Scattered Intel features: Linux defined, word 8. > > + * > > + * Note that the bit location of the SGX features is meaningful as KVM > > expects > > + * the Linux defined bit to match the Intel defined bit, e.g. > > X86_FEATURE_SGX1 > > + * must remain at bit 0, SGX2 at bit 1, etc... > > Eww, no. > > > + */ > > +#define X86_FEATURE_SGX1 ( 8*32+ 0) /* SGX1 leaf functions */ > > +#define X86_FEATURE_SGX2 ( 8*32+ 1) /* SGX2 leaf functions */ > > +/* Bits [0:7] are reserved for SGX */ > > That leaf has "Bits 31 - 07: Reserved." So what happens if they start > adding more bits there? We shoosh the other defines even further into > the word? > > Talk to your hw guys, if the plan is to leave those bits for other > feature flags, then let's allocate a new capability word for F12_EAX.
We tried that, you shot it down[*], hence these shenanigans. With respect to more SGX feature flags, the original changelog even stated "with more expected in the not-too-distant future". I'm not arguing that this isn't ugly, just want to make it clear that we're not wantonly throwing junk into the kernel. I'm all for a dedicated SGX word, it makes our lives easier. [*] https://lkml.kernel.org/r/[email protected]
