Re: [Xen-devel] [PATCH v8 09/24] x86: refactor psr: set value: assemble features value array.

[Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>]

On 17-03-10 02:15:20, Jan Beulich wrote:
> >>> On 10.03.17 at 04:21, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
> > On 17-03-08 09:54:04, Jan Beulich wrote:
> >> >>> On 15.02.17 at 09:49, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
> >> > @@ -207,6 +233,29 @@ static enum psr_feat_type 
> >> > psr_cbm_type_to_feat_type(enum cbm_type type)
> >> >      return feat_type;
> >> >  }
> >> >  
> >> > +static bool psr_check_cbm(unsigned int cbm_len, uint64_t cbm)
> >> > +{
> >> > +    unsigned int first_bit, zero_bit;
> >> > +
> >> > +    /* Set bits should only in the range of [0, cbm_len). */
> >> > +    if ( cbm & (~0ull << cbm_len) )
> >> 
> >> This will not do what you intend for cbm_len == 64.
> >> 
> > cbm_len is not 64. cbm_len means the CBM value length, how many bits. For L3
> > CAT, it may be 11 bits. For L2 CAT, it may be 8 bits.
> 
> And there is an _architectural_ guarantee for them to never
> reach 64 bits?
> 
Per SDM, 'EAX[4:0] reports the length of the capacity bitmask length'. So, we
get cbm_len in '*_init_feature' function as below.

#define CAT_CBM_LEN_MASK 0x1f
cat.cbm_len = (regs.a & CAT_CBM_LEN_MASK) + 1;

So, the max cbm_len is '32'.

BRs,
Sun Yi

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel