[PATCH] VT-d: prune super-page related capability macros

[Jan Beulich <jbeulich@xxxxxxxx>]

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>

--- 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)