[Xen-devel] [PATCH 1/2] x86/hvm/viridian: keep APIC assist page mapped...

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

... for the lifetime of the domain.

If Xen is to make use of the APIC assist enlightenment then a persistent
mapping needs to be kept, rather than the temporary one which is currently
used only to initialize the page content.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/hvm/viridian.c        | 54 +++++++++++++++++++++++++++-----------
 xen/include/asm-x86/hvm/viridian.h |  6 ++++-
 2 files changed, 43 insertions(+), 17 deletions(-)

diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
index 6bd844b..c779290 100644
--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -163,7 +163,7 @@ static void dump_apic_assist(const struct vcpu *v)
 {
     const union viridian_apic_assist *aa;
 
-    aa = &v->arch.hvm_vcpu.viridian.apic_assist;
+    aa = &v->arch.hvm_vcpu.viridian.apic_assist.msr;
 
     printk(XENLOG_G_INFO "%pv: VIRIDIAN APIC_ASSIST: enabled: %x pfn: %lx\n",
            v, aa->fields.enabled, (unsigned long)aa->fields.pfn);
@@ -217,9 +217,9 @@ static void enable_hypercall_page(struct domain *d)
 static void initialize_apic_assist(struct vcpu *v)
 {
     struct domain *d = v->domain;
-    unsigned long gmfn = v->arch.hvm_vcpu.viridian.apic_assist.fields.pfn;
+    unsigned long gmfn = v->arch.hvm_vcpu.viridian.apic_assist.msr.fields.pfn;
     struct page_info *page = get_page_from_gfn(d, gmfn, NULL, P2M_ALLOC);
-    uint8_t *p;
+    void *va;
 
     /*
      * We don't yet make use of the APIC assist page but by setting
@@ -231,21 +231,40 @@ static void initialize_apic_assist(struct vcpu *v)
      * details of how Windows uses the page.
      */
 
-    if ( !page || !get_page_type(page, PGT_writable_page) )
+    if ( !page )
+        return;
+
+    if ( !get_page_type(page, PGT_writable_page) )
     {
-        if ( page )
-            put_page(page);
-        gdprintk(XENLOG_WARNING, "Bad GMFN %lx (MFN %lx)\n", gmfn,
-                 page ? page_to_mfn(page) : INVALID_MFN);
+        put_page(page);
         return;
     }
 
-    p = __map_domain_page(page);
+    va = __map_domain_page_global(page);
+    if ( !va )
+    {
+        put_page_and_type(page);
+        return;
+    }
 
-    *(u32 *)p = 0;
+    *(uint32_t *)va = 0;
 
-    unmap_domain_page(p);
+    v->arch.hvm_vcpu.viridian.apic_assist.page = page;
+    v->arch.hvm_vcpu.viridian.apic_assist.va = va;
+}
+
+static void teardown_apic_assist(struct vcpu *v)
+{
+    struct page_info *page = v->arch.hvm_vcpu.viridian.apic_assist.page;
+    void *va = v->arch.hvm_vcpu.viridian.apic_assist.va;
+
+    if ( !va )
+        return;
+
+    v->arch.hvm_vcpu.viridian.apic_assist.va = NULL;
+    v->arch.hvm_vcpu.viridian.apic_assist.page = NULL;
 
+    unmap_domain_page_global(va);
     put_page_and_type(page);
 }
 
@@ -374,9 +393,9 @@ int wrmsr_viridian_regs(uint32_t idx, uint64_t val)
 
     case VIRIDIAN_MSR_APIC_ASSIST:
         perfc_incr(mshv_wrmsr_apic_msr);
-        v->arch.hvm_vcpu.viridian.apic_assist.raw = val;
+        v->arch.hvm_vcpu.viridian.apic_assist.msr.raw = val;
         dump_apic_assist(v);
-        if (v->arch.hvm_vcpu.viridian.apic_assist.fields.enabled)
+        if ( v->arch.hvm_vcpu.viridian.apic_assist.msr.fields.enabled )
             initialize_apic_assist(v);
         break;
 
@@ -485,7 +504,7 @@ int rdmsr_viridian_regs(uint32_t idx, uint64_t *val)
 
     case VIRIDIAN_MSR_APIC_ASSIST:
         perfc_incr(mshv_rdmsr_apic_msr);
-        *val = v->arch.hvm_vcpu.viridian.apic_assist.raw;
+        *val = v->arch.hvm_vcpu.viridian.apic_assist.msr.raw;
         break;
 
     case VIRIDIAN_MSR_REFERENCE_TSC:
@@ -530,6 +549,7 @@ int viridian_vcpu_init(struct vcpu *v)
 void viridian_vcpu_deinit(struct vcpu *v)
 {
     free_cpumask_var(v->arch.hvm_vcpu.viridian.flush_cpumask);
+    teardown_apic_assist(v);
 }
 
 int viridian_hypercall(struct cpu_user_regs *regs)
@@ -728,7 +748,7 @@ static int viridian_save_vcpu_ctxt(struct domain *d, 
hvm_domain_context_t *h)
     for_each_vcpu( d, v ) {
         struct hvm_viridian_vcpu_context ctxt;
 
-        ctxt.apic_assist = v->arch.hvm_vcpu.viridian.apic_assist.raw;
+        ctxt.apic_assist = v->arch.hvm_vcpu.viridian.apic_assist.msr.raw;
 
         if ( hvm_save_entry(VIRIDIAN_VCPU, v->vcpu_id, h, &ctxt) != 0 )
             return 1;
@@ -754,7 +774,9 @@ static int viridian_load_vcpu_ctxt(struct domain *d, 
hvm_domain_context_t *h)
     if ( hvm_load_entry(VIRIDIAN_VCPU, h, &ctxt) != 0 )
         return -EINVAL;
 
-    v->arch.hvm_vcpu.viridian.apic_assist.raw = ctxt.apic_assist;
+    v->arch.hvm_vcpu.viridian.apic_assist.msr.raw = ctxt.apic_assist;
+    if ( v->arch.hvm_vcpu.viridian.apic_assist.msr.fields.enabled )
+        initialize_apic_assist(v);
 
     return 0;
 }
diff --git a/xen/include/asm-x86/hvm/viridian.h 
b/xen/include/asm-x86/hvm/viridian.h
index 2eec85e..c60c113 100644
--- a/xen/include/asm-x86/hvm/viridian.h
+++ b/xen/include/asm-x86/hvm/viridian.h
@@ -21,7 +21,11 @@ union viridian_apic_assist
 
 struct viridian_vcpu
 {
-    union viridian_apic_assist apic_assist;
+    struct {
+        union viridian_apic_assist msr;
+        struct page_info *page;
+        void *va;
+    } apic_assist;
     cpumask_var_t flush_cpumask;
 };
 
-- 
2.1.4


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