Hi Babu,
Please modify subject prefix to "x86,fs/resctrl" since this adds new arch
API called by resctrl fs.
On 6/11/25 2:23 PM, Babu Moger wrote:
> Smart Data Cache Injection (SDCI) is a mechanism that enables direct
> insertion of data from I/O devices into the L3 cache. It can the demands
"It can the demands" -> "It can reduce demands"?
> on DRAM bandwidth and reduces latency to the processor consuming the I/O
> data.
>
> Introduce cache resource property "io_alloc_capable" that an architecture
> can set if a portion of the L3 cache can be allocated for I/O traffic.
I think "L3" should be dropped because the cache resource property is not
unique to L3. It is a property of all cache resources.
> Set this property on x86 systems that support SDCIAE (L3 Smart Data Cache
> Injection Allocation Enforcement).
Here it can be mentioned that this property is only set for the L3 cache
resource on systems that supports SDCIAE.
>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
> v6: No changes.
>
> v5: No changes.
>
> v4: Updated the commit message and code comment based on feedback.
>
> v3: Rewrote commit log. Changed the text to bit generic than the AMD specific.
> Renamed the rdt_get_sdciae_alloc_cfg() to rdt_set_io_alloc_capable().
> Removed leftover comment from v2.
>
> v2: Changed sdciae_capable to io_alloc_capable to make it generic feature.
> Also moved the io_alloc_capable in struct resctrl_cache.
> ---
> arch/x86/kernel/cpu/resctrl/core.c | 7 +++++++
> include/linux/resctrl.h | 3 +++
> 2 files changed, 10 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 326c679ade5c..a3d174362249 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -274,6 +274,11 @@ static void rdt_get_cdp_config(int level)
> rdt_resources_all[level].r_resctrl.cdp_capable = true;
> }
>
> +static void rdt_set_io_alloc_capable(struct rdt_resource *r)
> +{
> + r->cache.io_alloc_capable = true;
> +}
> +
> static void rdt_get_cdp_l3_config(void)
> {
> rdt_get_cdp_config(RDT_RESOURCE_L3);
> @@ -840,6 +845,8 @@ static __init bool get_rdt_alloc_resources(void)
> rdt_get_cache_alloc_cfg(1, r);
> if (rdt_cpu_has(X86_FEATURE_CDP_L3))
> rdt_get_cdp_l3_config();
> + if (rdt_cpu_has(X86_FEATURE_SDCIAE))
> + rdt_set_io_alloc_capable(r);
> ret = true;
> }
> if (rdt_cpu_has(X86_FEATURE_CAT_L2)) {
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 9ba771f2ddea..0e8641e41100 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -191,6 +191,8 @@ struct rdt_mon_domain {
> * @arch_has_sparse_bitmasks: True if a bitmask like f00f is valid.
> * @arch_has_per_cpu_cfg: True if QOS_CFG register for this cache
> * level has CPU scope.
> + * @io_alloc_capable: True if portion of the cache can be allocated
> + * for I/O traffic.
Reading this again I think the description can be improved since technically
resctrl does not allocate a portion of cache but instead configures the
portion of cache that device can allocate into.
So perhaps this can be: "True if portion of the cache can be configured
for I/O traffic allocation."
> */
> struct resctrl_cache {
> unsigned int cbm_len;
> @@ -198,6 +200,7 @@ struct resctrl_cache {
> unsigned int shareable_bits;
> bool arch_has_sparse_bitmasks;
> bool arch_has_per_cpu_cfg;
> + bool io_alloc_capable;
> };
>
> /**
Reinette
