[Xen-devel] [PATCH V2] x86/altp2m: propagate ept.ad changes to all active altp2ms

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

This patch is a pre-requisite for fixing the logdirty VGA issue
(display freezes when switching to a new altp2m view early in a
domain's lifetime), but sent separately for easier review.
The new ept_set_ad_sync() function has been added to update all
active altp2ms' ept.ad. New altp2ms will inherit the hostp2m's
ept.ad value. ept_set_ad_sync() is now also the code
responsible for locking updated p2ms.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
Suggested-by: George Dunlap <george.dunlap@xxxxxxxxxx>

---
Changes since V1:
 - Removed unnecessary p2m_lock() in p2m_init_altp2m_ept().
 - Changed value's type from int to bool.
 - Stopped treating the hostp2m interchangeably with
   d->arch.altp2m_p2m[0] in ept_set_ad_sync().
---
 xen/arch/x86/mm/p2m-ept.c | 54 ++++++++++++++++++++++++++++++++++++++++-------
 xen/arch/x86/mm/p2m.c     |  8 -------
 2 files changed, 46 insertions(+), 16 deletions(-)

diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index d376966..a5abd85 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -17,6 +17,7 @@
 
 #include <xen/domain_page.h>
 #include <xen/sched.h>
+#include <asm/altp2m.h>
 #include <asm/current.h>
 #include <asm/paging.h>
 #include <asm/types.h>
@@ -1218,34 +1219,69 @@ static void ept_tlb_flush(struct p2m_domain *p2m)
     ept_sync_domain_mask(p2m, p2m->domain->dirty_cpumask);
 }
 
+static void ept_set_ad_sync(struct p2m_domain *p2m, bool value)
+{
+    struct domain *d = p2m->domain;
+    struct p2m_domain *hostp2m = p2m_get_hostp2m(d);
+
+    p2m_lock(hostp2m);
+
+    hostp2m->ept.ad = value;
+
+    if ( unlikely(altp2m_active(d)) )
+    {
+        unsigned int i;
+
+        for ( i = 0; i < MAX_ALTP2M; i++ )
+        {
+            if ( d->arch.altp2m_eptp[i] == mfn_x(INVALID_MFN) )
+                continue;
+
+            p2m = d->arch.altp2m_p2m[i];
+
+            p2m_lock(p2m);
+            p2m->ept.ad = value;
+            p2m_unlock(p2m);
+        }
+    }
+
+    p2m_unlock(hostp2m);
+}
+
 static void ept_enable_pml(struct p2m_domain *p2m)
 {
+    struct domain *d = p2m->domain;
+
     /* Domain must have been paused */
-    ASSERT(atomic_read(&p2m->domain->pause_count));
+    ASSERT(atomic_read(&d->pause_count));
 
     /*
      * No need to return whether vmx_domain_enable_pml has succeeded, as
      * ept_p2m_type_to_flags will do the check, and write protection will be
      * used if PML is not enabled.
      */
-    if ( vmx_domain_enable_pml(p2m->domain) )
+    if ( vmx_domain_enable_pml(d) )
         return;
 
     /* Enable EPT A/D bit for PML */
-    p2m->ept.ad = 1;
-    vmx_domain_update_eptp(p2m->domain);
+    ept_set_ad_sync(p2m, true);
+
+    vmx_domain_update_eptp(d);
 }
 
 static void ept_disable_pml(struct p2m_domain *p2m)
 {
+    struct domain *d = p2m->domain;
+
     /* Domain must have been paused */
-    ASSERT(atomic_read(&p2m->domain->pause_count));
+    ASSERT(atomic_read(&d->pause_count));
 
-    vmx_domain_disable_pml(p2m->domain);
+    vmx_domain_disable_pml(d);
 
     /* Disable EPT A/D bit */
-    p2m->ept.ad = 0;
-    vmx_domain_update_eptp(p2m->domain);
+    ept_set_ad_sync(p2m, false);
+
+    vmx_domain_update_eptp(d);
 }
 
 static void ept_flush_pml_buffers(struct p2m_domain *p2m)
@@ -1386,8 +1422,10 @@ void setup_ept_dump(void)
 void p2m_init_altp2m_ept(struct domain *d, unsigned int i)
 {
     struct p2m_domain *p2m = d->arch.altp2m_p2m[i];
+    struct p2m_domain *hostp2m = p2m_get_hostp2m(d);
     struct ept_data *ept;
 
+    p2m->ept.ad = hostp2m->ept.ad;
     p2m->min_remapped_gfn = gfn_x(INVALID_GFN);
     p2m->max_remapped_gfn = 0;
     ept = &p2m->ept;
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index d6a8810..d90c624 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -360,11 +360,7 @@ void p2m_enable_hardware_log_dirty(struct domain *d)
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
 
     if ( p2m->enable_hardware_log_dirty )
-    {
-        p2m_lock(p2m);
         p2m->enable_hardware_log_dirty(p2m);
-        p2m_unlock(p2m);
-    }
 }
 
 void p2m_disable_hardware_log_dirty(struct domain *d)
@@ -372,11 +368,7 @@ void p2m_disable_hardware_log_dirty(struct domain *d)
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
 
     if ( p2m->disable_hardware_log_dirty )
-    {
-        p2m_lock(p2m);
         p2m->disable_hardware_log_dirty(p2m);
-        p2m_unlock(p2m);
-    }
 }
 
 void p2m_flush_hardware_cached_dirty(struct domain *d)
-- 
2.7.4


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