[xen stable-4.17] x86/intel: ensure Global Performance Counter Control is setup correctly

[patchbot@xxxxxxx]

commit d0ad2cc5eac1b5d3cfd14204d377ce2384f52607
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Fri Feb 2 08:02:20 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Feb 2 08:02:20 2024 +0100

    x86/intel: ensure Global Performance Counter Control is setup correctly
    
    When Architectural Performance Monitoring is available, the PERF_GLOBAL_CTRL
    MSR contains per-counter enable bits that is ANDed with the enable bit in 
the
    counter EVNTSEL MSR in order for a PMC counter to be enabled.
    
    So far the watchdog code seems to have relied on the PERF_GLOBAL_CTRL enable
    bits being set by default, but at least on some Intel Sapphire and Emerald
    Rapids this is no longer the case, and Xen reports:
    
    Testing NMI watchdog on all CPUs: 0 40 stuck
    
    The first CPU on each package is started with PERF_GLOBAL_CTRL zeroed, so 
PMC0
    doesn't start counting when the enable bit in EVNTSEL0 is set, due to the
    relevant enable bit in PERF_GLOBAL_CTRL not being set.
    
    Check and adjust PERF_GLOBAL_CTRL during CPU initialization so that all the
    general-purpose PMCs are enabled.  Doing so brings the state of the 
package-BSP
    PERF_GLOBAL_CTRL in line with the rest of the CPUs on the system.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 6bdb965178bbb3fc50cd4418d4770a7789956e2c
    master date: 2024-01-17 10:40:52 +0100
---
 xen/arch/x86/cpu/intel.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/cpu/intel.c b/xen/arch/x86/cpu/intel.c
index b40ac696e6..96723b5d44 100644
--- a/xen/arch/x86/cpu/intel.c
+++ b/xen/arch/x86/cpu/intel.c
@@ -528,9 +528,30 @@ static void cf_check init_intel(struct cpuinfo_x86 *c)
        init_intel_cacheinfo(c);
        if (c->cpuid_level > 9) {
                unsigned eax = cpuid_eax(10);
+               unsigned int cnt = (eax >> 8) & 0xff;
+
                /* Check for version and the number of counters */
-               if ((eax & 0xff) && (((eax>>8) & 0xff) > 1))
+               if ((eax & 0xff) && (cnt > 1) && (cnt <= 32)) {
+                       uint64_t global_ctrl;
+                       unsigned int cnt_mask = (1UL << cnt) - 1;
+
+                       /*
+                        * On (some?) Sapphire/Emerald Rapids platforms each
+                        * package-BSP starts with all the enable bits for the
+                        * general-purpose PMCs cleared.  Adjust so counters
+                        * can be enabled from EVNTSEL.
+                        */
+                       rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, global_ctrl);
+                       if ((global_ctrl & cnt_mask) != cnt_mask) {
+                               printk("CPU%u: invalid PERF_GLOBAL_CTRL: %#"
+                                      PRIx64 " adjusting to %#" PRIx64 "\n",
+                                      smp_processor_id(), global_ctrl,
+                                      global_ctrl | cnt_mask);
+                               wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL,
+                                      global_ctrl | cnt_mask);
+                       }
                        __set_bit(X86_FEATURE_ARCH_PERFMON, c->x86_capability);
+               }
        }
 
        if ( !cpu_has(c, X86_FEATURE_XTOPOLOGY) )
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.17