[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [PATCH] VT-d: prune super-page related capability macros
> From: Jan Beulich <jbeulich@xxxxxxxx> > Sent: Friday, November 12, 2021 5:51 PM > > cap_super_page_val() and cap_super_offset() are unused (apart from the > latter using the former). I don't see how cap_super_offset() can be > useful in its current shape: cap_super_page_val()'s result is not an > lvalue and hence can't have its address taken. Plus a user would have > to check the capability register field is non-zero, for > find_first_bit() (or find_first_set_bit(), if suitably corrected) to be > valid in the first place. Yet as per the spec when the field is non-zero > the low bit would always be set, so the result would be independent of > the actual value the field holds. > > Further zap cap_sps_512gb() and cap_sps_1tb(). While earlier versions > of the spec had things spelled out that way, the current version marks > the two bits as reserved. And "48-bit offset to page frame" wasn't in > line with 1Tb pages anyway - clearly 256Tb pages would have been meant > here. > > Finally properly parenthesize parameter uses in the remaining two > macros. > > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx> > > --- a/xen/drivers/passthrough/vtd/iommu.h > +++ b/xen/drivers/passthrough/vtd/iommu.h > @@ -68,13 +68,8 @@ > #define cap_num_fault_regs(c) ((((c) >> 40) & 0xff) + 1) > #define cap_pgsel_inv(c) (((c) >> 39) & 1) > > -#define cap_super_page_val(c) (((c) >> 34) & 0xf) > -#define cap_super_offset(c) (((find_first_bit(&cap_super_page_val(c), 4)) > \ > - * OFFSET_STRIDE) + 21) > -#define cap_sps_2mb(c) ((c >> 34) & 1) > -#define cap_sps_1gb(c) ((c >> 35) & 1) > -#define cap_sps_512gb(c) ((c >> 36) & 1) > -#define cap_sps_1tb(c) ((c >> 37) & 1) > +#define cap_sps_2mb(c) (((c) >> 34) & 1) > +#define cap_sps_1gb(c) (((c) >> 35) & 1) > > #define cap_fault_reg_offset(c) ((((c) >> 24) & 0x3ff) * 16) >
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