Re: [PATCH v7 31/49] x86/resctrl: Remove the limit on the number of CLOSID

[Fenghua Yu]

On 2/28/25 11:58, James Morse wrote:
> From: Amit Singh Tomar <amitsinght@xxxxxxxxxxx>
>
> Resctrl allocates and finds free CLOSID values using the bits of a u32.
> This restricts the number of control groups that can be created by
> user-space.
>
> MPAM has an architectural limit of 2^16 CLOSID values, Intel x86 could
> be extended beyond 32 values. There is at least one MPAM platform which
> supports more than 32 CLOSID values.
>
> Replace the fixed size bitmap with calls to the bitmap API to allocate
> an array of a sufficient size.
>
> ffs() returns '1' for bit 0, hence the existing code subtracts 1 from
> the index to get the CLOSID value. find_first_bit() returns the bit
> number which does not need adjusting.
>
> Signed-off-by: Amit Singh Tomar <amitsinght@xxxxxxxxxxx>
> [ morse: fixed the off-by-one in the allocator and the wrong
>   not-found value. Removed the limit. Rephrase the commit message. ]
> Signed-off-by: James Morse <james.morse@xxxxxxx>
Reviewed-by: Fenghua Yu <fenghuay@xxxxxxxxxx>


Thanks.


-Fenghua