[Xen-devel] [PATCH for-4.10] xen/dom0: Fix latent dom0 construction bugs on all architectures

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

 * x86 PV and ARM dom0's must not clear _VPF_down from v->pause_flags until
   all state is actually set up.  As it currently stands, d0v0 is eligible for
   scheduling before its registers have been set.  This is latent as we also
   hold a systemcontroller pause reference at the time which prevents d0 from
   being scheduled.

 * x86 PVH dom0's must set v->is_initialised on d0v0, to prevent another vcpu
   being able to call VCPUOP_initialise and modify state under the feet of the
   running vcpu.  This is latent as PVH dom0 construction don't yet function.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/arm/domain_build.c   |  6 +++---
 xen/arch/x86/dom0_build.c     | 13 +++++++++++--
 xen/arch/x86/hvm/dom0_build.c |  1 +
 xen/arch/x86/pv/dom0_build.c  |  6 +++---
 4 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 4636b17..bf29299 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2197,9 +2197,6 @@ int construct_dom0(struct domain *d)
 
     discard_initial_modules();
 
-    v->is_initialised = 1;
-    clear_bit(_VPF_down, &v->pause_flags);
-
     memset(regs, 0, sizeof(*regs));
 
     regs->pc = (register_t)kinfo.entry;
@@ -2247,6 +2244,9 @@ int construct_dom0(struct domain *d)
             vcpu_switch_to_aarch64_mode(d->vcpu[i]);
     }
 
+    v->is_initialised = 1;
+    clear_bit(_VPF_down, &v->pause_flags);
+
     return 0;
 }
 
diff --git a/xen/arch/x86/dom0_build.c b/xen/arch/x86/dom0_build.c
index e4bffd5..bf992fe 100644
--- a/xen/arch/x86/dom0_build.c
+++ b/xen/arch/x86/dom0_build.c
@@ -466,6 +466,8 @@ int __init construct_dom0(struct domain *d, const module_t 
*image,
                           void *(*bootstrap_map)(const module_t *),
                           char *cmdline)
 {
+    int rc;
+
     /* Sanity! */
     BUG_ON(d->domain_id != 0);
     BUG_ON(d->vcpu[0] == NULL);
@@ -481,8 +483,15 @@ int __init construct_dom0(struct domain *d, const module_t 
*image,
     }
 #endif
 
-    return (is_hvm_domain(d) ? dom0_construct_pvh : dom0_construct_pv)
-           (d, image, image_headroom, initrd,bootstrap_map, cmdline);
+    rc = (is_hvm_domain(d) ? dom0_construct_pvh : dom0_construct_pv)
+         (d, image, image_headroom, initrd, bootstrap_map, cmdline);
+    if ( rc )
+        return rc;
+
+    /* Sanity! */
+    BUG_ON(!d->vcpu[0]->is_initialised);
+
+    return 0;
 }
 
 /*
diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index e8f746c..a67071c 100644
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -614,6 +614,7 @@ static int __init pvh_setup_cpus(struct domain *d, paddr_t 
entry,
 
     update_domain_wallclock_time(d);
 
+    v->is_initialised = 1;
     clear_bit(_VPF_down, &v->pause_flags);
 
     return 0;
diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c
index dcbee43..8ad7e3d 100644
--- a/xen/arch/x86/pv/dom0_build.c
+++ b/xen/arch/x86/pv/dom0_build.c
@@ -847,9 +847,6 @@ int __init dom0_construct_pv(struct domain *d,
 
     update_domain_wallclock_time(d);
 
-    v->is_initialised = 1;
-    clear_bit(_VPF_down, &v->pause_flags);
-
     /*
      * Initial register values:
      *  DS,ES,FS,GS = FLAT_KERNEL_DS
@@ -883,6 +880,9 @@ int __init dom0_construct_pv(struct domain *d,
     if ( d->domain_id == hardware_domid )
         iommu_hwdom_init(d);
 
+    v->is_initialised = 1;
+    clear_bit(_VPF_down, &v->pause_flags);
+
     return 0;
 
 out:
-- 
2.1.4


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