[Xen-devel] [PATCH v5 08/13] x86: add scheduling support for Intel CAT

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

On context switch, write the the domain's Class of Service(COS) to MSR
IA32_PQR_ASSOC, to notify hardware to use the new COS.

For performance reason, the COS mask for current cpu is also cached in
the local per-CPU variable.

Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
---
Changes in v5:
* Remove the need to cache socket.
Changes in v2:
* merge common scheduling changes into scheduling improvement patch.
* use readable expr for psra->cos_mask.
---
 xen/arch/x86/psr.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/psr.c b/xen/arch/x86/psr.c
index 2b08269..ac1c2b7 100644
--- a/xen/arch/x86/psr.c
+++ b/xen/arch/x86/psr.c
@@ -37,6 +37,7 @@ struct psr_cat_socket_info {
 
 struct psr_assoc {
     uint64_t val;
+    uint64_t cos_mask;
 };
 
 struct psr_cmt *__read_mostly psr_cmt;
@@ -200,7 +201,17 @@ static inline void psr_assoc_init(void)
 {
     struct psr_assoc *psra = &this_cpu(psr_assoc);
 
-    if ( psr_cmt_enabled() )
+    if ( cat_socket_info )
+    {
+        struct psr_cat_socket_info *info = cat_socket_info +
+                                           cpu_to_socket(smp_processor_id());
+
+        if ( info->enabled )
+            psra->cos_mask = ((1ull << get_count_order(info->cos_max)) - 1)
+                             << 32;
+    }
+
+    if ( psr_cmt_enabled() || psra->cos_mask )
         rdmsrl(MSR_IA32_PSR_ASSOC, psra->val);
 }
 
@@ -209,6 +220,12 @@ static inline void psr_assoc_rmid(uint64_t *reg, unsigned 
int rmid)
     *reg = (*reg & ~rmid_mask) | (rmid & rmid_mask);
 }
 
+static inline void psr_assoc_cos(uint64_t *reg, unsigned int cos,
+                                 uint64_t cos_mask)
+{
+    *reg = (*reg & ~cos_mask) | (((uint64_t)cos << 32) & cos_mask);
+}
+
 void psr_ctxt_switch_to(struct domain *d)
 {
     struct psr_assoc *psra = &this_cpu(psr_assoc);
@@ -217,6 +234,11 @@ void psr_ctxt_switch_to(struct domain *d)
     if ( psr_cmt_enabled() )
         psr_assoc_rmid(&reg, d->arch.psr_rmid);
 
+    if ( psra->cos_mask )
+        psr_assoc_cos(&reg, d->arch.psr_cos_ids ?
+                      d->arch.psr_cos_ids[cpu_to_socket(smp_processor_id())] :
+                      0, psra->cos_mask);
+
     if ( reg != psra->val )
     {
         wrmsrl(MSR_IA32_PSR_ASSOC, reg);
-- 
1.9.1


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