[Xen-devel] [PATCH] xen/x86: vpmu: Unmap per-vCPU PMU page when the domain is destroyed

[Paul Durrant <pdurrant@xxxxxxxxxx>]

From: Julien Grall <jgrall@xxxxxxxxxx>

A guest will setup a shared page with the hypervisor for each vCPU via
XENPMU_init. The page will then get mapped in the hypervisor and only
released when XEMPMU_finish is called.

This means that if the guest is not shutdown gracefully (such as via xl
destroy), the page will stay mapped in the hypervisor. One of the
consequence is the domain can never be fully destroyed as some of its
memory is still mapped.

As Xen should never rely on the guest to correctly clean-up any
allocation in the hypervisor, we should also unmap pages during the
domain destruction if there are any left.

We can re-use the same logic as in pvpmu_finish(). To avoid
duplication, move the logic in a new function that can also be called
from vpmu_destroy().

NOTE: The call to vpmu_destroy() must also be moved from
      arch_vcpu_destroy() into domain_relinquish_resources() such that the
      mapped page does not prevent domain_destroy() (which calls
      arch_vcpu_destroy()) from being called.

Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wl@xxxxxxx>
Cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/cpu/vpmu.c | 45 +++++++++++++++++++++++------------------
 xen/arch/x86/domain.c   |  6 +++---
 2 files changed, 28 insertions(+), 23 deletions(-)

diff --git a/xen/arch/x86/cpu/vpmu.c b/xen/arch/x86/cpu/vpmu.c
index f397183ec3..9ae4ed48c8 100644
--- a/xen/arch/x86/cpu/vpmu.c
+++ b/xen/arch/x86/cpu/vpmu.c
@@ -578,9 +578,32 @@ static void vpmu_arch_destroy(struct vcpu *v)
     }
 }
 
-void vpmu_destroy(struct vcpu *v)
+static void vpmu_cleanup(struct vcpu *v)
 {
+    struct vpmu_struct *vpmu = vcpu_vpmu(v);
+    mfn_t mfn;
+    void *xenpmu_data;
+
+    spin_lock(&vpmu->vpmu_lock);
+
     vpmu_arch_destroy(v);
+    xenpmu_data = vpmu->xenpmu_data;
+    vpmu->xenpmu_data = NULL;
+
+    spin_unlock(&vpmu->vpmu_lock);
+
+    if ( xenpmu_data )
+    {
+        mfn = domain_page_map_to_mfn(xenpmu_data);
+        ASSERT(mfn_valid(mfn));
+        unmap_domain_page_global(xenpmu_data);
+        put_page_and_type(mfn_to_page(mfn));
+    }
+}
+
+void vpmu_destroy(struct vcpu *v)
+{
+    vpmu_cleanup(v);
 
     put_vpmu(v);
 }
@@ -639,9 +662,6 @@ static int pvpmu_init(struct domain *d, xen_pmu_params_t 
*params)
 static void pvpmu_finish(struct domain *d, xen_pmu_params_t *params)
 {
     struct vcpu *v;
-    struct vpmu_struct *vpmu;
-    mfn_t mfn;
-    void *xenpmu_data;
 
     if ( (params->vcpu >= d->max_vcpus) || (d->vcpu[params->vcpu] == NULL) )
         return;
@@ -650,22 +670,7 @@ static void pvpmu_finish(struct domain *d, 
xen_pmu_params_t *params)
     if ( v != current )
         vcpu_pause(v);
 
-    vpmu = vcpu_vpmu(v);
-    spin_lock(&vpmu->vpmu_lock);
-
-    vpmu_arch_destroy(v);
-    xenpmu_data = vpmu->xenpmu_data;
-    vpmu->xenpmu_data = NULL;
-
-    spin_unlock(&vpmu->vpmu_lock);
-
-    if ( xenpmu_data )
-    {
-        mfn = domain_page_map_to_mfn(xenpmu_data);
-        ASSERT(mfn_valid(mfn));
-        unmap_domain_page_global(xenpmu_data);
-        put_page_and_type(mfn_to_page(mfn));
-    }
+    vpmu_cleanup(v);
 
     if ( v != current )
         vcpu_unpause(v);
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index f1dd86e12e..1d75b2e6c3 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -454,9 +454,6 @@ void arch_vcpu_destroy(struct vcpu *v)
     xfree(v->arch.msrs);
     v->arch.msrs = NULL;
 
-    if ( !is_idle_domain(v->domain) )
-        vpmu_destroy(v);
-
     if ( is_hvm_vcpu(v) )
         hvm_vcpu_destroy(v);
     else
@@ -2224,6 +2221,9 @@ int domain_relinquish_resources(struct domain *d)
     if ( is_hvm_domain(d) )
         hvm_domain_relinquish_resources(d);
 
+    for_each_vcpu ( d, v )
+        vpmu_destroy(v);
+
     return 0;
 }
 
-- 
2.20.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel