Re: [PATCH v6 09/24] x86/resctrl: Use set_bit()/clear_bit() instead of open coding

Reinette Chatre
2023-10-03T21:14:35Z

Hi James,

On 9/14/2023 10:21 AM, James Morse wrote:
> The resctrl CLOSID allocator uses a single 32bit word to track which
> CLOSID are free. The setting and clearing of bits is open coded.
>
> A subsequent patch adds resctrl_closid_is_free(), which adds more open

resctrl_closid_is_free() is not added in this series.

> coded bitmaps operations. These will eventually need changing to use
> the bitops helpers so that a CLOSID bitmap of the correct size can be
> allocated dynamically.
>
> Convert the existing open coded bit manipulations of closid_free_map
> to use set_bit() and friends.
>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Tested-By: Peter Newman <peternewman@google.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index ac1a6437469f..fa449ee0d1a7 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -106,7 +106,7 @@ void rdt_staged_configs_clear(void)
> * - Our choices on how to configure each resource become progressively more
> * limited as the number of resources grows.
> */
> -static int closid_free_map;
> +static unsigned long closid_free_map;
> static int closid_free_map_len;
>
> int closids_supported(void)
> @@ -126,7 +126,7 @@ static void closid_init(void)
> closid_free_map = BIT_MASK(rdt_min_closid) - 1;
>
> /* CLOSID 0 is always reserved for the default group */
> - closid_free_map &= ~1;
> + clear_bit(0, &closid_free_map);
> closid_free_map_len = rdt_min_closid;
> }
>
> @@ -137,14 +137,14 @@ static int closid_alloc(void)
> if (closid == 0)
> return -ENOSPC;
> closid--;
> - closid_free_map &= ~(1 << closid);
> + clear_bit(closid, &closid_free_map);
>
> return closid;
> }
>
> void closid_free(int closid)
> {
> - closid_free_map |= 1 << closid;
> + set_bit(closid, &closid_free_map);
> }
>
> /**
> @@ -156,7 +156,7 @@ void closid_free(int closid)
> */
> static bool closid_allocated(unsigned int closid)
> {
> - return (closid_free_map & (1 << closid)) == 0;
> + return !test_bit(closid, &closid_free_map);
> }
>
> /**

The patch looks good to me.

Reinette