[Devel] [PATCH RHEL8 COMMIT] x86: Show vcpu cpuflags in cpuinfo

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-193.6.3.vz8.4.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-193.6.3.vz8.4.15
------>
commit e651dcf4b551ca9e85737914b5059681b71a2e77
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Tue Nov 3 16:32:59 2020 +0300

    x86: Show vcpu cpuflags in cpuinfo
    
    Show cpu_i flags as flags of vcpu_i.
    
    Extracted from "Initial patch". Merged several reworks.
    
    TODO: Maybe replace/rework on_each_cpu() with smp_call_function_single().
    Then we won't need split c_start() in previous patch (as the call
    function will be called right before specific cpu is being prepared
    to show). This should be rather easy.
    [aryabinin: Don't see what it buys us, so I didn't try to implement it]
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    
    https://jira.sw.ru/browse/PSBM-121823
    
    [aryabinin:vz8 rebase]
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
    Reviewed-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 arch/x86/kernel/cpu/proc.c | 63 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 59 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index d6b17a60acf6..4fe1577d5e6f 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -4,6 +4,8 @@
 #include <linux/string.h>
 #include <linux/seq_file.h>
 #include <linux/cpufreq.h>
+#include <linux/sched.h>
+#include <linux/ve_proto.h>
 
 #include "cpu.h"
 
@@ -58,10 +60,54 @@ extern void __do_cpuid_fault(unsigned int op, unsigned int count,
 			     unsigned int *eax, unsigned int *ebx,
 			     unsigned int *ecx, unsigned int *edx);
 
+struct cpu_flags {
+	u32 val[NCAPINTS];
+};
+
+static DEFINE_PER_CPU(struct cpu_flags, cpu_flags);
+
+static void init_cpu_flags(void *dummy)
+{
+	int cpu = smp_processor_id();
+	struct cpu_flags *flags = &per_cpu(cpu_flags, cpu);
+	struct cpuinfo_x86 *c = &cpu_data(cpu);
+	unsigned int eax, ebx, ecx, edx;
+
+	memcpy(flags->val, c->x86_capability, NCAPINTS * sizeof(u32));
+
+	/*
+	 * Clear feature bits masked using cpuid masking/faulting.
+	 */
+
+	if (c->cpuid_level >= 0x00000001) {
+		__do_cpuid_fault(0x00000001, 0, &eax, &ebx, &ecx, &edx);
+		flags->val[4] &= ecx;
+		flags->val[0] &= edx;
+	}
+
+	if (c->cpuid_level >= 0x00000007) {
+		__do_cpuid_fault(0x00000007, 0, &eax, &ebx, &ecx, &edx);
+		flags->val[9] &= ebx;
+	}
+
+	if ((c->extended_cpuid_level & 0xffff0000) == 0x80000000 &&
+	    c->extended_cpuid_level >= 0x80000001) {
+		__do_cpuid_fault(0x80000001, 0, &eax, &ebx, &ecx, &edx);
+		flags->val[6] &= ecx;
+		flags->val[1] &= edx;
+	}
+
+	if (c->cpuid_level >= 0x0000000d) {
+		__do_cpuid_fault(0x0000000d, 1, &eax, &ebx, &ecx, &edx);
+		flags->val[10] &= eax;
+	}
+}
+
 static int show_cpuinfo(struct seq_file *m, void *v)
 {
 	struct cpuinfo_x86 *c = v;
 	unsigned int cpu;
+	int is_super = ve_is_super(get_exec_env());
 	int i;
 
 	cpu = c->cpu_index;
@@ -103,7 +149,10 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 
 	seq_puts(m, "flags\t\t:");
 	for (i = 0; i < 32*NCAPINTS; i++)
-		if (cpu_has(c, i) && x86_cap_flags[i] != NULL)
+		if (x86_cap_flags[i] != NULL &&
+				((is_super && cpu_has(c, i)) ||
+				 (!is_super && test_bit(i, (unsigned long *)
+							&per_cpu(cpu_flags, cpu)))))
 			seq_printf(m, " %s", x86_cap_flags[i]);
 
 	seq_puts(m, "\nbugs\t\t:");
@@ -145,18 +194,24 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 	return 0;
 }
 
-static void *c_start(struct seq_file *m, loff_t *pos)
+static void *__c_start(struct seq_file *m, loff_t *pos)
 {
 	*pos = cpumask_next(*pos - 1, cpu_online_mask);
-	if ((*pos) < nr_cpu_ids)
+	if (bitmap_weight(cpumask_bits(cpu_online_mask), *pos) < num_online_vcpus())
 		return &cpu_data(*pos);
 	return NULL;
 }
 
+static void *c_start(struct seq_file *m, loff_t *pos)
+{
+	on_each_cpu(init_cpu_flags, NULL, 1);
+	return __c_start(m, pos);
+}
+
 static void *c_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	(*pos)++;
-	return c_start(m, pos);
+	return __c_start(m, pos);
 }
 
 static void c_stop(struct seq_file *m, void *v)