[Xen-devel] [PATCH v4 10/26] xen/x86: Improve disabling of features which have dependencies

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

APIC and XSAVE have dependent features, which also need disabling if Xen
chooses to disable a feature.

Use setup_clear_cpu_cap() rather than clear_bit(), as it takes care of
dependent features as well.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <JBeulich@xxxxxxxx>
---
v2: Move boolean_param() adjacent to use_xsave in xstate_init()
---
 xen/arch/x86/apic.c       |  2 +-
 xen/arch/x86/cpu/common.c | 12 +++---------
 xen/arch/x86/xstate.c     |  6 +++++-
 3 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/xen/arch/x86/apic.c b/xen/arch/x86/apic.c
index b9601ad..8df5bd3 100644
--- a/xen/arch/x86/apic.c
+++ b/xen/arch/x86/apic.c
@@ -1349,7 +1349,7 @@ void pmu_apic_interrupt(struct cpu_user_regs *regs)
 int __init APIC_init_uniprocessor (void)
 {
     if (enable_local_apic < 0)
-        __clear_bit(X86_FEATURE_APIC, boot_cpu_data.x86_capability);
+        setup_clear_cpu_cap(X86_FEATURE_APIC);
 
     if (!smp_found_config && !cpu_has_apic) {
         skip_ioapic_setup = 1;
diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 0942b44..b5c023f 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -16,9 +16,6 @@
 
 #include "cpu.h"
 
-static bool_t use_xsave = 1;
-boolean_param("xsave", use_xsave);
-
 bool_t opt_arat = 1;
 boolean_param("arat", opt_arat);
 
@@ -341,12 +338,6 @@ void identify_cpu(struct cpuinfo_x86 *c)
        if (this_cpu->c_init)
                this_cpu->c_init(c);
 
-        /* Initialize xsave/xrstor features */
-       if ( !use_xsave )
-               __clear_bit(X86_FEATURE_XSAVE, boot_cpu_data.x86_capability);
-
-       if ( cpu_has_xsave )
-               xstate_init(c);
 
        if ( !opt_pku )
                setup_clear_cpu_cap(X86_FEATURE_PKU);
@@ -370,6 +361,9 @@ void identify_cpu(struct cpuinfo_x86 *c)
 
        /* Now the feature flags better reflect actual CPU features! */
 
+       if ( cpu_has_xsave )
+               xstate_init(c);
+
 #ifdef NOISY_CAPS
        printk(KERN_DEBUG "CPU: After all inits, caps:");
        for (i = 0; i < NCAPINTS; i++)
diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index f649405..5060704 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -502,11 +502,15 @@ unsigned int xstate_ctxt_size(u64 xcr0)
 /* Collect the information of processor's extended state */
 void xstate_init(struct cpuinfo_x86 *c)
 {
+    static bool_t __initdata use_xsave = 1;
+    boolean_param("xsave", use_xsave);
+
     bool_t bsp = c == &boot_cpu_data;
     u32 eax, ebx, ecx, edx;
     u64 feature_mask;
 
-    if ( boot_cpu_data.cpuid_level < XSTATE_CPUID )
+    if ( (bsp && !use_xsave) ||
+         boot_cpu_data.cpuid_level < XSTATE_CPUID )
     {
         BUG_ON(!bsp);
         setup_clear_cpu_cap(X86_FEATURE_XSAVE);
-- 
2.1.4


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