Commit eb8ed28f authored by James Morse's avatar James Morse Committed by Jonathan Corbet

Documentation: x86: Contiguous cbm isn't all X86

Since commit 4d05bf71 ("x86/resctrl: Introduce AMD QOS feature")
resctrl has supported non-contiguous cache bit masks. The interface
for this is currently try-it-and-see.

Update the documentation to say Intel CPUs have this requirement,
instead of X86.

Cc: Babu Moger <Babu.Moger@amd.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 22aac857
...@@ -342,7 +342,7 @@ For cache resources we describe the portion of the cache that is available ...@@ -342,7 +342,7 @@ For cache resources we describe the portion of the cache that is available
for allocation using a bitmask. The maximum value of the mask is defined for allocation using a bitmask. The maximum value of the mask is defined
by each cpu model (and may be different for different cache levels). It by each cpu model (and may be different for different cache levels). It
is found using CPUID, but is also provided in the "info" directory of is found using CPUID, but is also provided in the "info" directory of
the resctrl file system in "info/{resource}/cbm_mask". X86 hardware the resctrl file system in "info/{resource}/cbm_mask". Intel hardware
requires that these masks have all the '1' bits in a contiguous block. So requires that these masks have all the '1' bits in a contiguous block. So
0x3, 0x6 and 0xC are legal 4-bit masks with two bits set, but 0x5, 0x9 0x3, 0x6 and 0xC are legal 4-bit masks with two bits set, but 0x5, 0x9
and 0xA are not. On a system with a 20-bit mask each bit represents 5% and 0xA are not. On a system with a 20-bit mask each bit represents 5%
......
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