[v4,1/2] x86/hvm/viridian: keep APIC assist page mapped...

Commit Message

Paul Durrant March 17, 2016, 8:37 a.m. UTC

... 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.

This patch also adds a comment block at the top of the source with
information on the latest version of the spec. from Microsoft and the
current URL where it may be found.

Signed-off-by: Paul Durrant <[e-mail]>
Cc: Keir Fraser <[e-mail]>
Cc: Jan Beulich <[e-mail]>
Cc: Andrew Cooper <[e-mail]>
---

v4:
 - Added missing teardown required if the MSR is re-written.

v2:
 - Re-instated warning if the initialization of an APIC assist page fails.
 - Added up-to-date information about the viridian specification to the
   comment block at the top of the source.
---
 xen/arch/x86/hvm/hvm.c             |  2 +
 xen/arch/x86/hvm/viridian.c        | 77 ++++++++++++++++++++++++++++----------
 xen/include/asm-x86/hvm/viridian.h |  8 +++-
 3 files changed, 66 insertions(+), 21 deletions(-)

Comments

Andrew Cooper March 17, 2016, 10:50 a.m. UTC | #1

On 17/03/16 08:37, Paul Durrant wrote:
> ... 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.
>
> This patch also adds a comment block at the top of the source with
> information on the latest version of the spec. from Microsoft and the
> current URL where it may be found.
>
> Signed-off-by: Paul Durrant <[e-mail]>
> Cc: Keir Fraser <[e-mail]>
> Cc: Jan Beulich <[e-mail]>
> Cc: Andrew Cooper <[e-mail]>

By the looks of it, this patch textually depends on your Viridian TLB fixes?

Reviewed-by: Andrew Cooper <[e-mail]>

Paul Durrant March 17, 2016, 11:13 a.m. UTC | #2

> -----Original Message-----
> From: Andrew Cooper [mailto:[e-mail]]
> Sent: 17 March 2016 10:51
> To: Paul Durrant; [e-mail]
> Cc: Keir (Xen.org); Jan Beulich
> Subject: Re: [PATCH v4 1/2] x86/hvm/viridian: keep APIC assist page
> mapped...
> 
> On 17/03/16 08:37, Paul Durrant wrote:
> > ... 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.
> >
> > This patch also adds a comment block at the top of the source with
> > information on the latest version of the spec. from Microsoft and the
> > current URL where it may be found.
> >
> > Signed-off-by: Paul Durrant <[e-mail]>
> > Cc: Keir Fraser <[e-mail]>
> > Cc: Jan Beulich <[e-mail]>
> > Cc: Andrew Cooper <[e-mail]>
> 
> By the looks of it, this patch textually depends on your Viridian TLB fixes?
> 

Yes, this series is based on my branch including the fix, so it should be applied afterwards.

> Reviewed-by: Andrew Cooper <[e-mail]>

Thanks,

  Paul

Jan Beulich March 17, 2016, 11:58 a.m. UTC | #3

>>> On 17.03.16 at 09:37, <[e-mail]> wrote:
> +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);
>  }

The apic_assist.page field is needed only here, and is redundant
with the va being stored (from which it can be derived via
domain_page_map_to_mfn()). Please let's avoid needlessly
growing struct vcpu.

Jan

Paul Durrant March 17, 2016, noon UTC | #4

> -----Original Message-----
> From: Jan Beulich [mailto:[e-mail]]
> Sent: 17 March 2016 11:59
> To: Paul Durrant
> Cc: Andrew Cooper; [e-mail]; Keir (Xen.org)
> Subject: Re: [PATCH v4 1/2] x86/hvm/viridian: keep APIC assist page
> mapped...
> 
> >>> On 17.03.16 at 09:37, <[e-mail]> wrote:
> > +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);
> >  }
> 
> The apic_assist.page field is needed only here, and is redundant
> with the va being stored (from which it can be derived via
> domain_page_map_to_mfn()). Please let's avoid needlessly
> growing struct vcpu.
> 

Ok. I'll drop it then.

  Paul

> Jan

Patch

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 4ea51d7..f446ee4 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2606,6 +2606,8 @@  int hvm_vcpu_initialise(struct vcpu *v)
 
 void hvm_vcpu_destroy(struct vcpu *v)
 {
+    viridian_vcpu_deinit(v);
+
     hvm_all_ioreq_servers_remove_vcpu(v->domain, v);
 
     if ( hvm_altp2m_supported() )
diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
index 1ee22aa..b809118 100644
--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -1,7 +1,12 @@ 
 /******************************************************************************
  * viridian.c
  *
- * An implementation of the Viridian hypercall interface.
+ * An implementation of some Viridian enlightenments. See Microsoft's
+ * Hypervisor Top Level Functional Specification (v4.0b) at:
+ *
+ * https://msdn.microsoft.com/en-us/virtualization/hyperv_on_windows/develop/tlfs
+ *
+ * for more information.
  */
 
 #include <xen/sched.h>
@@ -163,7 +168,7 @@  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 +222,9 @@  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
@@ -227,25 +232,49 @@  static void initialize_apic_assist(struct vcpu *v)
      * bound to support the MSR. We therefore do just enough to keep windows
      * happy.
      *
-     * See http://msdn.microsoft.com/en-us/library/ff538657%28VS.85%29.aspx for
-     * details of how Windows uses the page.
+     * See section 13.3.4.1 of the specification for details of this
+     * enlightenment.
      */
 
-    if ( !page || !get_page_type(page, PGT_writable_page) )
+    if ( !page )
+        goto fail;
+
+    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);
-        return;
+        put_page(page);
+        goto fail;
     }
 
-    p = __map_domain_page(page);
+    va = __map_domain_page_global(page);
+    if ( !va )
+    {
+        put_page_and_type(page);
+        goto fail;
+    }
 
-    *(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;
+    return;
+
+ fail:
+    gdprintk(XENLOG_WARNING, "Bad GMFN %lx (MFN %lx)\n", gmfn,
+             page ? page_to_mfn(page) : INVALID_MFN);
+}
+
+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 +403,10 @@  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;
+        teardown_apic_assist(v); /* release any previous mapping */
+        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 +515,7 @@  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:
@@ -521,6 +551,11 @@  int rdmsr_viridian_regs(uint32_t idx, uint64_t *val)
     return 1;
 }
 
+void viridian_vcpu_deinit(struct vcpu *v)
+{
+    teardown_apic_assist(v);
+}
+
 static DEFINE_PER_CPU(cpumask_t, ipi_cpumask);
 
 int viridian_hypercall(struct cpu_user_regs *regs)
@@ -721,7 +756,7 @@  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;
@@ -747,7 +782,9 @@  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 c4319d7..ee3a120 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;
 };
 
 union viridian_guest_os_id
@@ -117,6 +121,8 @@  viridian_hypercall(struct cpu_user_regs *regs);
 void viridian_time_ref_count_freeze(struct domain *d);
 void viridian_time_ref_count_thaw(struct domain *d);
 
+void viridian_vcpu_deinit(struct vcpu *v);
+
 #endif /* __ASM_X86_HVM_VIRIDIAN_H__ */
 
 /*