x86/resctrl: Add struct rdt_membw::arch_needs_linear to explain AMD/Intel MBA difference

The configuration values user-space provides to the resctrl filesystem
are ABI. To make this work on another architecture, all the ABI bits
should be moved out of /arch/x86 and under /fs.

To do this, the differences between AMD and Intel CPUs needs to be
explained to resctrl via resource properties, instead of function
pointers that let the arch code accept subtly different values on
different platforms/architectures.

For MBA, Intel CPUs reject configuration attempts for non-linear
resources, whereas AMD ignore this field as its MBA resource is never
linear. To merge the parse/validate functions, this difference needs to
be explained.

Add struct rdt_membw::arch_needs_linear to indicate the arch code needs
the linear property to be true to configure this resource. AMD can set
this and delay_linear to false. Intel can set arch_needs_linear to
true to keep the existing "No support for non-linear MB domains" error
message for affected platforms.

 [ bp: convert "we" etc to passive voice. ]

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Link: https://lkml.kernel.org/r/20200708163929.2783-8-james.morse@arm.com

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 9225ee5cca6fee52a61f87744511c1ede1d5210b..52b8991de8a31f9ddf7362b36709f37bcd83ac16 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -260,6 +260,7 @@ static bool __get_mem_config_intel(struct rdt_resource *r)
        r->num_closid = edx.split.cos_max + 1;
        max_delay = eax.split.max_delay + 1;
        r->default_ctrl = MAX_MBA_BW;
+       r->membw.arch_needs_linear = true;
        if (ecx & MBA_IS_LINEAR) {
                r->membw.delay_linear = true;
                r->membw.min_bw = MAX_MBA_BW - max_delay;
@@ -267,6 +268,7 @@ static bool __get_mem_config_intel(struct rdt_resource *r)
        } else {
                if (!rdt_get_mb_table(r))
                        return false;
+               r->membw.arch_needs_linear = false;
        }
        r->data_width = 3;
 
@@ -288,6 +290,7 @@ static bool __rdt_get_mem_config_amd(struct rdt_resource *r)
 
        /* AMD does not use delay */
        r->membw.delay_linear = false;
+       r->membw.arch_needs_linear = false;
 
        r->membw.min_bw = 0;
        r->membw.bw_gran = 1;

diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 934c8fb8a64a7d7131e3ec089828bdcd65e1e8fc..e3bcd77add2bf51db0b3b43fc8536a17485f4a5f 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -33,6 +33,12 @@ static bool bw_validate_amd(char *buf, unsigned long *data,
        unsigned long bw;
        int ret;
 
+       /* temporary: always false on AMD */
+       if (!r->membw.delay_linear && r->membw.arch_needs_linear) {
+               rdt_last_cmd_puts("No support for non-linear MB domains\n");
+               return false;
+       }
+
        ret = kstrtoul(buf, 10, &bw);
        if (ret) {
                rdt_last_cmd_printf("Non-decimal digit in MB value %s\n", buf);
@@ -82,7 +88,7 @@ static bool bw_validate(char *buf, unsigned long *data, struct rdt_resource *r)
        /*
         * Only linear delay values is supported for current Intel SKUs.
         */
-       if (!r->membw.delay_linear) {
+       if (!r->membw.delay_linear && r->membw.arch_needs_linear) {
                rdt_last_cmd_puts("No support for non-linear MB domains\n");
                return false;
        }

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 1eb39bd24990d50509bbbbf6dbc52d6d05452da2..7b0072397a11e0aca17d3d29649ab896fd9dfa40 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -372,6 +372,7 @@ struct rdt_cache {
  * @min_bw:            Minimum memory bandwidth percentage user can request
  * @bw_gran:           Granularity at which the memory bandwidth is allocated
  * @delay_linear:      True if memory B/W delay is in linear scale
+ * @arch_needs_linear: True if we can't configure non-linear resources
  * @mba_sc:            True if MBA software controller(mba_sc) is enabled
  * @mb_map:            Mapping of memory B/W percentage to memory B/W delay
  */
@@ -379,6 +380,7 @@ struct rdt_membw {
        u32             min_bw;
        u32             bw_gran;
        u32             delay_linear;
+       bool            arch_needs_linear;
        bool            mba_sc;
        u32             *mb_map;
 };