[Xen-devel] [PATCH v4 16/39] arm/p2m: Add HVMOP_altp2m_destroy_p2m

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---
v2: Substituted the call to tlb_flush for p2m_flush_table.
    Added comments.
    Cosmetic fixes.

v3: Changed the locking mechanism to "p2m_write_lock" inside the
    function "altp2m_destroy_by_id".

    Do not flush but rather teardown the altp2m in the function
    "altp2m_destroy_by_id".

    Exchanged the check "altp2m_vttbr[idx] == INVALID_VTTBR" for
    "altp2m_p2m[idx] == NULL" in "altp2m_destroy_by_id".

v4: Removed locking the p2m in "altp2m_destroy_by_id" as the p2m is not
    used by anyone else at this point.
---
 xen/arch/arm/altp2m.c        | 39 +++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/hvm.c           |  2 +-
 xen/include/asm-arm/altp2m.h |  4 ++++
 3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/altp2m.c b/xen/arch/arm/altp2m.c
index 6b1e34709f..1128e1af16 100644
--- a/xen/arch/arm/altp2m.c
+++ b/xen/arch/arm/altp2m.c
@@ -180,6 +180,45 @@ void altp2m_flush_complete(struct domain *d)
     altp2m_unlock(d);
 }
 
+int altp2m_destroy_by_id(struct domain *d, unsigned int idx)
+{
+    struct p2m_domain *p2m;
+    int rc = -EBUSY;
+
+    /*
+     * The altp2m[0] is considered as the hostp2m and is used as a safe harbor
+     * to which you can switch as long as altp2m is active. After deactivating
+     * altp2m, the system switches back to the original hostp2m view. That is,
+     * altp2m[0] should only be destroyed/flushed/freed, when altp2m is
+     * deactivated.
+     */
+    if ( !idx || idx >= MAX_ALTP2M )
+        return rc;
+
+    domain_pause_except_self(d);
+
+    altp2m_lock(d);
+
+    if ( d->arch.altp2m_p2m[idx] != NULL )
+    {
+        p2m = d->arch.altp2m_p2m[idx];
+
+        if ( !_atomic_read(p2m->active_vcpus) )
+        {
+            p2m_teardown_one(p2m);
+            xfree(p2m);
+            d->arch.altp2m_p2m[idx] = NULL;
+            rc = 0;
+        }
+    }
+
+    altp2m_unlock(d);
+
+    domain_unpause_except_self(d);
+
+    return rc;
+}
+
 void altp2m_teardown(struct domain *d)
 {
     unsigned int i;
diff --git a/xen/arch/arm/hvm.c b/xen/arch/arm/hvm.c
index caa2e1b516..4bf2f28a1a 100644
--- a/xen/arch/arm/hvm.c
+++ b/xen/arch/arm/hvm.c
@@ -131,7 +131,7 @@ static int do_altp2m_op(XEN_GUEST_HANDLE_PARAM(void) arg)
         break;
 
     case HVMOP_altp2m_destroy_p2m:
-        rc = -EOPNOTSUPP;
+        rc = altp2m_destroy_by_id(d, a.u.view.view);
         break;
 
     case HVMOP_altp2m_switch_p2m:
diff --git a/xen/include/asm-arm/altp2m.h b/xen/include/asm-arm/altp2m.h
index b9719f9d5b..778c6c4f12 100644
--- a/xen/include/asm-arm/altp2m.h
+++ b/xen/include/asm-arm/altp2m.h
@@ -60,4 +60,8 @@ int altp2m_init_next_available(struct domain *d,
 /* Flush all the alternate p2m's for a domain. */
 void altp2m_flush_complete(struct domain *d);
 
+/* Make a specific alternate p2m invalid */
+int altp2m_destroy_by_id(struct domain *d,
+                         unsigned int idx);
+
 #endif /* __ASM_ARM_ALTP2M_H */
-- 
2.13.3


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