Re: [PATCH v3 02/19] x86/resctrl: Access per-rmid structures by index

Reinette Chatre
2023-03-31T23:20:32Z

Hi James,

On 3/20/2023 10:26 AM, James Morse wrote:
> Because of the differences between Intel RDT/AMD QoS and Arm's MPAM
> monitors, RMID values on arm64 are not unique unless the CLOSID is
> also included. Bitmaps like rmid_busy_llc need to be sized by the
> number of unique entries for this resource.
>
> Add helpers to encode/decode the CLOSID and RMID to an index. The
> domain's rmid_busy__llc and the rmid_ptrs[] array are then sized by

rmid_busy__llc -> rmid_busy_llc

Not a big deal but since you are using [] for rmid_ptrs[] it should
not be necessary to say that it is an array.

> index, as are the domain mbm_local and mbm_total arrays.
> On x86, the index is always just the RMID, so all these structures
> remain the same size.
>
> The index gives resctrl a unique value it can use to store monitor
> values, and allows MPAM to decode the closid when reading the hardware
> counters.

When you are switching between CLOSID and closid in the same context it
is less obvious that it means the same thing.

>
> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> Changes since v1:
> * Added X86_BAD_CLOSID macro to make it clear what this value means
> * Added second WARN_ON() for closid checking, and made both _ONCE()
>
> Changes since v2:
> * Added RESCTRL_RESERVED_CLOSID
> * Removed a newline
> * Repharsed some comments
> * Renamed a variable 'ignore'd
> * Moved X86_RESCTRL_BAD_CLOSID to a previous patch
> ---
> arch/x86/include/asm/resctrl.h | 17 ++++++
> arch/x86/kernel/cpu/resctrl/core.c | 2 +-
> arch/x86/kernel/cpu/resctrl/internal.h | 1 +
> arch/x86/kernel/cpu/resctrl/monitor.c | 83 +++++++++++++++++---------
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 7 ++-
> include/linux/resctrl.h | 3 +
> 6 files changed, 82 insertions(+), 31 deletions(-)
>
> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> index cbe986d23df6..3ca40be41a0a 100644
> --- a/arch/x86/include/asm/resctrl.h
> +++ b/arch/x86/include/asm/resctrl.h
> @@ -101,6 +101,23 @@ static inline void resctrl_sched_in(void)
> __resctrl_sched_in();
> }
>
> +static inline u32 resctrl_arch_system_num_rmid_idx(void)
> +{
> + /* RMID are independent numbers for x86. num_rmid_idx==num_rmid */

Could you add spaces around the "=="?

> + return boot_cpu_data.x86_cache_max_rmid + 1;
> +}
> +
> +static inline void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid)
> +{
> + *rmid = idx;
> + *closid = X86_RESCTRL_BAD_CLOSID;
> +}
> +
> +static inline u32 resctrl_arch_rmid_idx_encode(u32 ignored, u32 rmid)
> +{
> + return rmid;
> +}
> +
> void resctrl_cpu_detect(struct cpuinfo_x86 *c);
>
> #else
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 030d3b409768..351319403f84 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -600,7 +600,7 @@ static void clear_closid_rmid(int cpu)
> state->default_rmid = 0;
> state->cur_closid = 0;
> state->cur_rmid = 0;
> - wrmsr(MSR_IA32_PQR_ASSOC, 0, 0);
> + wrmsr(MSR_IA32_PQR_ASSOC, RESCTRL_RESERVED_CLOSID, 0);
> }
>
> static int resctrl_online_cpu(unsigned int cpu)
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index c64097947994..47506e2afd59 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -7,6 +7,7 @@
> #include <linux/kernfs.h>
> #include <linux/fs_context.h>
> #include <linux/jump_label.h>
> +#include <asm/resctrl.h>
>
> #define L3_QOS_CDP_ENABLE 0x01ULL
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 18c37d364030..03a7d13dd653 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -142,12 +142,29 @@ static inline u64 get_corrected_mbm_count(u32 rmid, unsigned long val)
> return val;
> }
>
> -static inline struct rmid_entry *__rmid_entry(u32 closid, u32 rmid)
> +/*
> + * x86 and arm64 differ in their handling of monitoring.
> + * x86's RMID are an independent number, there is only one source of traffic
> + * an RMID value of '1'.

"source of traffic an RMID" -> "source of traffic with an RMID" ?

> + * arm64's PMG extend the PARTID/CLOSID space, there are multiple sources of
> + * traffic with a PMG value of '1', one for each CLOSID, meaining the RMID

meaining -> meaning

> + * value is no longer unique.

Reinette