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Message-ID: <548b542ff537936cc8a20f721f6f2472189c536d.1749677012.git.babu.moger@amd.com>
Date: Wed, 11 Jun 2025 16:23:29 -0500
From: Babu Moger <babu.moger@....com>
To: <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
<reinette.chatre@...el.com>, <Dave.Martin@....com>, <james.morse@....com>,
<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <akpm@...ux-foundation.org>,
<paulmck@...nel.org>, <rostedt@...dmis.org>, <thuth@...hat.com>,
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<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v6 4/8] x86/resctrl: Implement "io_alloc" enable/disable handlers
"io_alloc" enables direct insertion of data from I/O devices into the L3
cache.
On AMD, "io_alloc" feature is backed by L3 Smart Data Cache Injection
Allocation Enforcement (SDCIAE). Change SDCIAE state by setting (to enable)
or clearing (to disable) bit 1 of MSR L3_QOS_EXT_CFG on all logical
processors within the cache domain.
Introduce architecture-specific handlers to enable and disable the feature.
The SDCIAE feature details are available in APM listed below [1].
[1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
Publication # 24593 Revision 3.41 section 19.4.7 L3 Smart Data Cache
Injection Allocation Enforcement (SDCIAE)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Signed-off-by: Babu Moger <babu.moger@....com>
---
v6: Added lockdep_assert_cpus_held() in _resctrl_sdciae_enable() to protect
r->ctrl_domains.
Added more comments in include/linux/resctrl.h.
v5: Resolved conflicts due to recent resctrl FS/ARCH code restructure.
The files monitor.c/rdtgroup.c have been split between FS and ARCH directories.
Moved prototypes of resctrl_arch_io_alloc_enable() and
resctrl_arch_get_io_alloc_enabled() to include/linux/resctrl.h.
v4: Updated the commit log to address the feedback.
v3: Passed the struct rdt_resource to resctrl_arch_get_io_alloc_enabled() instead of resource id.
Renamed the _resctrl_io_alloc_enable() to _resctrl_sdciae_enable() as it is arch specific.
Changed the return to void in _resctrl_sdciae_enable() instead of int.
Added more context in commit log and fixed few typos.
v2: Renamed the functions to simplify the code.
Renamed sdciae_capable to io_alloc_capable.
Changed the name of few arch functions similar to ABMC series.
resctrl_arch_get_io_alloc_enabled()
resctrl_arch_io_alloc_enable()
---
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/kernel/cpu/resctrl/internal.h | 5 ++++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 40 ++++++++++++++++++++++++++
include/linux/resctrl.h | 21 ++++++++++++++
4 files changed, 67 insertions(+)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index b7dded3c8113..b92b04fa9888 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -1215,6 +1215,7 @@
/* - AMD: */
#define MSR_IA32_MBA_BW_BASE 0xc0000200
#define MSR_IA32_SMBA_BW_BASE 0xc0000280
+#define MSR_IA32_L3_QOS_EXT_CFG 0xc00003ff
#define MSR_IA32_EVT_CFG_BASE 0xc0000400
/* AMD-V MSRs */
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 5e3c41b36437..cfa519ea2875 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -37,6 +37,9 @@ struct arch_mbm_state {
u64 prev_msr;
};
+/* Setting bit 1 in L3_QOS_EXT_CFG enables the SDCIAE feature. */
+#define SDCIAE_ENABLE_BIT 1
+
/**
* struct rdt_hw_ctrl_domain - Arch private attributes of a set of CPUs that share
* a resource for a control function
@@ -102,6 +105,7 @@ struct msr_param {
* @mon_scale: cqm counter * mon_scale = occupancy in bytes
* @mbm_width: Monitor width, to detect and correct for overflow.
* @cdp_enabled: CDP state of this resource
+ * @sdciae_enabled: SDCIAE feature is enabled
*
* Members of this structure are either private to the architecture
* e.g. mbm_width, or accessed via helpers that provide abstraction. e.g.
@@ -115,6 +119,7 @@ struct rdt_hw_resource {
unsigned int mon_scale;
unsigned int mbm_width;
bool cdp_enabled;
+ bool sdciae_enabled;
};
static inline struct rdt_hw_resource *resctrl_to_arch_res(struct rdt_resource *r)
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 885026468440..3bdcd53b3ce3 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -229,6 +229,46 @@ bool resctrl_arch_get_cdp_enabled(enum resctrl_res_level l)
return rdt_resources_all[l].cdp_enabled;
}
+inline bool resctrl_arch_get_io_alloc_enabled(struct rdt_resource *r)
+{
+ return resctrl_to_arch_res(r)->sdciae_enabled;
+}
+
+static void resctrl_sdciae_set_one_amd(void *arg)
+{
+ bool *enable = arg;
+
+ if (*enable)
+ msr_set_bit(MSR_IA32_L3_QOS_EXT_CFG, SDCIAE_ENABLE_BIT);
+ else
+ msr_clear_bit(MSR_IA32_L3_QOS_EXT_CFG, SDCIAE_ENABLE_BIT);
+}
+
+static void _resctrl_sdciae_enable(struct rdt_resource *r, bool enable)
+{
+ struct rdt_ctrl_domain *d;
+
+ /* Walking r->ctrl_domains, ensure it can't race with cpuhp */
+ lockdep_assert_cpus_held();
+
+ /* Update L3_QOS_EXT_CFG MSR on all the CPUs in all domains */
+ list_for_each_entry(d, &r->ctrl_domains, hdr.list)
+ on_each_cpu_mask(&d->hdr.cpu_mask, resctrl_sdciae_set_one_amd, &enable, 1);
+}
+
+int resctrl_arch_io_alloc_enable(struct rdt_resource *r, bool enable)
+{
+ struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
+
+ if (hw_res->r_resctrl.cache.io_alloc_capable &&
+ hw_res->sdciae_enabled != enable) {
+ _resctrl_sdciae_enable(r, enable);
+ hw_res->sdciae_enabled = enable;
+ }
+
+ return 0;
+}
+
void resctrl_arch_reset_all_ctrls(struct rdt_resource *r)
{
struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 0e8641e41100..06e8a1821702 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -531,6 +531,27 @@ void resctrl_arch_reset_rmid_all(struct rdt_resource *r, struct rdt_mon_domain *
*/
void resctrl_arch_reset_all_ctrls(struct rdt_resource *r);
+/**
+ * resctrl_arch_io_alloc_enable() - Enable/disable io_alloc feature.
+ * @r: The resctrl resource.
+ * @enable: Enable (true) or disable (false) io_alloc on resource @r.
+ *
+ * This can be called from any CPU.
+ *
+ * Return:
+ * 0 on success, or non-zero on error.
+ */
+int resctrl_arch_io_alloc_enable(struct rdt_resource *r, bool enable);
+
+/**
+ * resctrl_arch_get_io_alloc_enabled() - Get io_alloc feature state.
+ * @r: The resctrl resource.
+ *
+ * Return:
+ * true if io_alloc is enabled or false if disabled.
+ */
+inline bool resctrl_arch_get_io_alloc_enabled(struct rdt_resource *r);
+
extern unsigned int resctrl_rmid_realloc_threshold;
extern unsigned int resctrl_rmid_realloc_limit;
--
2.34.1
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