Xen's implementation of PSR only supports Intel CPUs right now, hence it can be
made dependant on CONFIG_INTEL build option.
Since platform implementation is not limited to single vendor, intermediate
option CONFIG_X86_PSR introduced, which selected by CONFIG_INTEL.

When !X86_PSR then PSR-related sysctls XEN_SYSCTL_psr_cmt_op &
XEN_SYSCTL_psr_alloc are off as well.

Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
---
v5 patch here:
https://lore.kernel.org/xen-devel/20240918091517.1200080-1-Sergiy_Kibrik@epam.com/

changes in v6:
 - rename option PSR -> X86_PSR
 - add help text for X86_PSR option and default value
 - do not force X86_PSR option by 'select'
changes in v5:
 - simplify psr_cmt_enabled()
 - move PSR config option and add description
changes in v4:
 - introduced CONFIG_PSR
 - changed description
 - changes to psr stubs
---
 xen/arch/x86/Kconfig           | 10 ++++++++++
 xen/arch/x86/Makefile          |  2 +-
 xen/arch/x86/domctl.c          |  3 +++
 xen/arch/x86/include/asm/psr.h | 10 ++++++++--
 xen/arch/x86/sysctl.c          |  4 +++-
 5 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 62f0b5e0f4..924b60cfcc 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -231,6 +231,16 @@ config TBOOT
 
 	  If unsure, stay with the default.
 
+config X86_PSR
+	bool "Platform Shared Resource support" if EXPERT
+	default INTEL
+	help
+	  Support of Platform Shared Resource technology, which is basis for
+	  monitoring and control of resources like cache and memory bandwidth.
+	  See xl-psr documentation for details.
+
+	  If unsure, stay with the default.
+
 choice
 	prompt "Alignment of Xen image"
 	default XEN_ALIGN_2M if PV_SHIM_EXCLUSIVE
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 286c003ec3..76ffe5a561 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -57,7 +57,7 @@ obj-y += pci.o
 obj-y += percpu.o
 obj-y += physdev.o
 obj-$(CONFIG_COMPAT) += x86_64/physdev.o
-obj-y += psr.o
+obj-$(CONFIG_X86_PSR) += psr.o
 obj-y += setup.o
 obj-y += shutdown.o
 obj-y += smp.o
diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 68b5b46d1a..6c1355e378 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -1195,6 +1195,7 @@ long arch_do_domctl(
     case XEN_DOMCTL_psr_alloc:
         switch ( domctl->u.psr_alloc.cmd )
         {
+#ifdef CONFIG_X86_PSR
         case XEN_DOMCTL_PSR_SET_L3_CBM:
             ret = psr_set_val(d, domctl->u.psr_alloc.target,
                               domctl->u.psr_alloc.data,
@@ -1257,6 +1258,8 @@ long arch_do_domctl(
 
 #undef domctl_psr_get_val
 
+#endif /* CONFIG_X86_PSR */
+
         default:
             ret = -EOPNOTSUPP;
             break;
diff --git a/xen/arch/x86/include/asm/psr.h b/xen/arch/x86/include/asm/psr.h
index 51df78794c..d21a59d98f 100644
--- a/xen/arch/x86/include/asm/psr.h
+++ b/xen/arch/x86/include/asm/psr.h
@@ -69,12 +69,11 @@ extern struct psr_cmt *psr_cmt;
 
 static inline bool psr_cmt_enabled(void)
 {
-    return !!psr_cmt;
+    return IS_ENABLED(CONFIG_X86_PSR) && psr_cmt;
 }
 
 int psr_alloc_rmid(struct domain *d);
 void psr_free_rmid(struct domain *d);
-void psr_ctxt_switch_to(struct domain *d);
 
 int psr_get_info(unsigned int socket, enum psr_type type,
                  uint32_t data[], unsigned int array_len);
@@ -83,8 +82,15 @@ int psr_get_val(struct domain *d, unsigned int socket,
 int psr_set_val(struct domain *d, unsigned int socket,
                 uint64_t new_val, enum psr_type type);
 
+#ifdef CONFIG_X86_PSR
+void psr_ctxt_switch_to(struct domain *d);
 void psr_domain_init(struct domain *d);
 void psr_domain_free(struct domain *d);
+#else
+static inline void psr_ctxt_switch_to(struct domain *d) {}
+static inline void psr_domain_init(struct domain *d) {}
+static inline void psr_domain_free(struct domain *d) {}
+#endif
 
 #endif /* __ASM_PSR_H__ */
 
diff --git a/xen/arch/x86/sysctl.c b/xen/arch/x86/sysctl.c
index 1d40d82c5a..1b04947516 100644
--- a/xen/arch/x86/sysctl.c
+++ b/xen/arch/x86/sysctl.c
@@ -225,10 +225,11 @@ long arch_do_sysctl(
 
     case XEN_SYSCTL_psr_alloc:
     {
-        uint32_t data[PSR_INFO_ARRAY_SIZE] = { };
+        uint32_t __maybe_unused data[PSR_INFO_ARRAY_SIZE] = { };
 
         switch ( sysctl->u.psr_alloc.cmd )
         {
+#ifdef CONFIG_X86_PSR
         case XEN_SYSCTL_PSR_get_l3_info:
             ret = psr_get_info(sysctl->u.psr_alloc.target,
                                PSR_TYPE_L3_CBM, data, ARRAY_SIZE(data));
@@ -279,6 +280,7 @@ long arch_do_sysctl(
             if ( __copy_field_to_guest(u_sysctl, sysctl, u.psr_alloc) )
                 ret = -EFAULT;
             break;
+#endif /* CONFIG_X86_PSR */
 
         default:
             ret = -EOPNOTSUPP;
-- 
2.25.1

On 26.09.2024 12:26, Sergiy Kibrik wrote:
> Xen's implementation of PSR only supports Intel CPUs right now, hence it can be
> made dependant on CONFIG_INTEL build option.
> Since platform implementation is not limited to single vendor, intermediate
> option CONFIG_X86_PSR introduced, which selected by CONFIG_INTEL.
> 
> When !X86_PSR then PSR-related sysctls XEN_SYSCTL_psr_cmt_op &
> XEN_SYSCTL_psr_alloc are off as well.
> 
> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>