[xen master] viridian: allow vCPU hotplug for Windows VMs

[patchbot@xxxxxxx]

commit 7e5cffcd1e9300cab46a1816b5eb676caaeed2c1
Author:     Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
AuthorDate: Fri Jan 29 14:18:43 2021 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jan 29 14:18:43 2021 +0100

    viridian: allow vCPU hotplug for Windows VMs
    
    If Viridian extensions are enabled, Windows wouldn't currently allow
    a hotplugged vCPU to be brought up dynamically. We need to expose a special
    bit to let the guest know we allow it. Hide it behind an option to stay
    on the safe side regarding compatibility with existing guests but
    nevertheless set the option on by default.
    
    Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
    Reviewed-by: Paul Durrant <paul@xxxxxxx>
    Acked-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 docs/man/xl.cfg.5.pod.in             | 7 ++++++-
 tools/include/libxl.h                | 6 ++++++
 tools/libs/light/libxl_types.idl     | 1 +
 tools/libs/light/libxl_x86.c         | 4 ++++
 xen/arch/x86/hvm/viridian/viridian.c | 5 ++++-
 xen/include/public/hvm/params.h      | 7 ++++++-
 6 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index 3467eae2cd..7cdb8595d3 100644
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -2267,11 +2267,16 @@ explicitly have any limits on the number of Virtual 
processors a guest
 is allowed to bring up. It is strongly recommended to keep this enabled
 for guests with more than 64 vCPUs.
 
+=item B<cpu_hotplug>
+
+This set enables dynamic changes to Virtual processor states in Windows
+guests effectively allowing vCPU hotplug.
+
 =item B<defaults>
 
 This is a special value that enables the default set of groups, which
 is currently the B<base>, B<freq>, B<time_ref_count>, B<apic_assist>,
-B<crash_ctl>, B<stimer> and B<no_vp_limit> groups.
+B<crash_ctl>, B<stimer>, B<no_vp_limit> and B<cpu_hotplug> groups.
 
 =item B<all>
 
diff --git a/tools/include/libxl.h b/tools/include/libxl.h
index ee15c0495c..547ddd3085 100644
--- a/tools/include/libxl.h
+++ b/tools/include/libxl.h
@@ -457,6 +457,12 @@
  */
 #define LIBXL_HAVE_VIRIDIAN_NO_VP_LIMIT 1
 
+/*
+ * LIBXL_HAVE_VIRIDIAN_CPU_HOTPLUG indicates that the 'cpu_hotplug' value
+ * is present in the viridian enlightenment enumeration.
+ */
+#define LIBXL_HAVE_VIRIDIAN_CPU_HOTPLUG 1
+
 /*
  * LIBXL_HAVE_DEVICE_PCI_LIST_FREE indicates that the
  * libxl_device_pci_list_free() function is defined.
diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
index 087a3db6e2..37fe61f3ec 100644
--- a/tools/libs/light/libxl_types.idl
+++ b/tools/libs/light/libxl_types.idl
@@ -240,6 +240,7 @@ libxl_viridian_enlightenment = 
Enumeration("viridian_enlightenment", [
     (9, "hcall_ipi"),
     (10, "ex_processor_masks"),
     (11, "no_vp_limit"),
+    (12, "cpu_hotplug"),
     ])
 
 libxl_hdtype = Enumeration("hdtype", [
diff --git a/tools/libs/light/libxl_x86.c b/tools/libs/light/libxl_x86.c
index 5c4c194c65..91a9fc72ed 100644
--- a/tools/libs/light/libxl_x86.c
+++ b/tools/libs/light/libxl_x86.c
@@ -310,6 +310,7 @@ static int hvm_set_viridian_features(libxl__gc *gc, 
uint32_t domid,
         libxl_bitmap_set(&enlightenments, 
LIBXL_VIRIDIAN_ENLIGHTENMENT_APIC_ASSIST);
         libxl_bitmap_set(&enlightenments, 
LIBXL_VIRIDIAN_ENLIGHTENMENT_CRASH_CTL);
         libxl_bitmap_set(&enlightenments, 
LIBXL_VIRIDIAN_ENLIGHTENMENT_NO_VP_LIMIT);
+        libxl_bitmap_set(&enlightenments, 
LIBXL_VIRIDIAN_ENLIGHTENMENT_CPU_HOTPLUG);
     }
 
     libxl_for_each_set_bit(v, info->u.hvm.viridian_enable) {
@@ -373,6 +374,9 @@ static int hvm_set_viridian_features(libxl__gc *gc, 
uint32_t domid,
     if (libxl_bitmap_test(&enlightenments, 
LIBXL_VIRIDIAN_ENLIGHTENMENT_NO_VP_LIMIT))
         mask |= HVMPV_no_vp_limit;
 
+    if (libxl_bitmap_test(&enlightenments, 
LIBXL_VIRIDIAN_ENLIGHTENMENT_CPU_HOTPLUG))
+        mask |= HVMPV_cpu_hotplug;
+
     if (mask != 0 &&
         xc_hvm_param_set(CTX->xch,
                          domid,
diff --git a/xen/arch/x86/hvm/viridian/viridian.c 
b/xen/arch/x86/hvm/viridian/viridian.c
index ae1ea8630b..b906f7b86a 100644
--- a/xen/arch/x86/hvm/viridian/viridian.c
+++ b/xen/arch/x86/hvm/viridian/viridian.c
@@ -76,6 +76,7 @@ typedef union _HV_CRASH_CTL_REG_CONTENTS
 } HV_CRASH_CTL_REG_CONTENTS;
 
 /* Viridian CPUID leaf 3, Hypervisor Feature Indication */
+#define CPUID3D_CPU_DYNAMIC_PARTITIONING (1 << 3)
 #define CPUID3D_CRASH_MSRS (1 << 10)
 #define CPUID3D_SINT_POLLING (1 << 17)
 
@@ -179,8 +180,10 @@ void cpuid_viridian_leaves(const struct vcpu *v, uint32_t 
leaf,
         res->a = u.lo;
         res->b = u.hi;
 
+        if ( viridian_feature_mask(d) & HVMPV_cpu_hotplug )
+           res->d = CPUID3D_CPU_DYNAMIC_PARTITIONING;
         if ( viridian_feature_mask(d) & HVMPV_crash_ctl )
-            res->d = CPUID3D_CRASH_MSRS;
+            res->d |= CPUID3D_CRASH_MSRS;
         if ( viridian_feature_mask(d) & HVMPV_synic )
             res->d |= CPUID3D_SINT_POLLING;
 
diff --git a/xen/include/public/hvm/params.h b/xen/include/public/hvm/params.h
index 805f4ca44c..c9d6e70d7b 100644
--- a/xen/include/public/hvm/params.h
+++ b/xen/include/public/hvm/params.h
@@ -172,6 +172,10 @@
 #define _HVMPV_no_vp_limit 11
 #define HVMPV_no_vp_limit (1 << _HVMPV_no_vp_limit)
 
+/* Enable vCPU hotplug */
+#define _HVMPV_cpu_hotplug 12
+#define HVMPV_cpu_hotplug (1 << _HVMPV_cpu_hotplug)
+
 #define HVMPV_feature_mask \
         (HVMPV_base_freq | \
          HVMPV_no_freq | \
@@ -184,7 +188,8 @@
          HVMPV_stimer | \
          HVMPV_hcall_ipi | \
          HVMPV_ex_processor_masks | \
-         HVMPV_no_vp_limit)
+         HVMPV_no_vp_limit | \
+         HVMPV_cpu_hotplug)
 
 #endif
 
--
generated by git-patchbot for /home/xen/git/xen.git#master