[PATCH v4 17/26] x86/pv: Provide custom cpumasks for PV domains

[Andrew Cooper <andrew.cooper3@citrix.com>]

And use them in preference to cpumask_defaults on context switch.  HVM domains
must not be masked (to avoid interfering with cpuid calls within the guest),
so always lazily context switch to the host default.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <JBeulich@suse.com>
---
v2:
 * s/cpumasks/cpuidmasks/
 * Use structure assignment
 * Fix error path in arch_domain_create()
v3:
 * Indentation fixes.
 * Only allocate PV cpuidmasks if the host is has cpumasks to use.
---
 xen/arch/x86/cpu/amd.c       |  4 +++-
 xen/arch/x86/cpu/intel.c     |  5 ++++-
 xen/arch/x86/domain.c        | 14 ++++++++++++++
 xen/include/asm-x86/domain.h |  2 ++
 4 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index 484d4b0..8cb04f0 100644
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -206,7 +206,9 @@ static void __init noinline probe_masking_msrs(void)
 static void amd_ctxt_switch_levelling(const struct domain *nextd)
 {
 	struct cpuidmasks *these_masks = &this_cpu(cpuidmasks);
-	const struct cpuidmasks *masks = &cpuidmask_defaults;
+	const struct cpuidmasks *masks =
+		(nextd && is_pv_domain(nextd) && nextd->arch.pv_domain.cpuidmasks)
+		? nextd->arch.pv_domain.cpuidmasks : &cpuidmask_defaults;
 
 #define LAZY(cap, msr, field)						\
 	({								\
diff --git a/xen/arch/x86/cpu/intel.c b/xen/arch/x86/cpu/intel.c
index 71b1199..00a9987 100644
--- a/xen/arch/x86/cpu/intel.c
+++ b/xen/arch/x86/cpu/intel.c
@@ -154,13 +154,16 @@ static void __init probe_masking_msrs(void)
 static void intel_ctxt_switch_levelling(const struct domain *nextd)
 {
 	struct cpuidmasks *these_masks = &this_cpu(cpuidmasks);
-	const struct cpuidmasks *masks = &cpuidmask_defaults;
+	const struct cpuidmasks *masks;
 
 	if (cpu_has_cpuid_faulting) {
 		set_cpuid_faulting(nextd && is_pv_domain(nextd));
 		return;
 	}
 
+	masks = (nextd && is_pv_domain(nextd) && nextd->arch.pv_domain.cpuidmasks)
+		? nextd->arch.pv_domain.cpuidmasks : &cpuidmask_defaults;
+
 #define LAZY(msr, field)						\
 	({								\
 		if (unlikely(these_masks->field != masks->field) &&	\
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index abc7194..d0d9773 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -577,6 +577,14 @@ int arch_domain_create(struct domain *d, unsigned int domcr_flags,
             goto fail;
         clear_page(d->arch.pv_domain.gdt_ldt_l1tab);
 
+        if ( levelling_caps & ~LCAP_faulting )
+        {
+            d->arch.pv_domain.cpuidmasks = xmalloc(struct cpuidmasks);
+            if ( !d->arch.pv_domain.cpuidmasks )
+                goto fail;
+            *d->arch.pv_domain.cpuidmasks = cpuidmask_defaults;
+        }
+
         rc = create_perdomain_mapping(d, GDT_LDT_VIRT_START,
                                       GDT_LDT_MBYTES << (20 - PAGE_SHIFT),
                                       NULL, NULL);
@@ -672,7 +680,10 @@ int arch_domain_create(struct domain *d, unsigned int domcr_flags,
         paging_final_teardown(d);
     free_perdomain_mappings(d);
     if ( is_pv_domain(d) )
+    {
+        xfree(d->arch.pv_domain.cpuidmasks);
         free_xenheap_page(d->arch.pv_domain.gdt_ldt_l1tab);
+    }
     psr_domain_free(d);
     return rc;
 }
@@ -692,7 +703,10 @@ void arch_domain_destroy(struct domain *d)
 
     free_perdomain_mappings(d);
     if ( is_pv_domain(d) )
+    {
         free_xenheap_page(d->arch.pv_domain.gdt_ldt_l1tab);
+        xfree(d->arch.pv_domain.cpuidmasks);
+    }
 
     free_xenheap_page(d->shared_info);
     cleanup_domain_irq_mapping(d);
diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index de60def..90f021f 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -252,6 +252,8 @@ struct pv_domain
 
     /* map_domain_page() mapping cache. */
     struct mapcache_domain mapcache;
+
+    struct cpuidmasks *cpuidmasks;
 };
 
 struct monitor_write_data {
-- 
2.1.4


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