[Qemu-devel] [PULL 10/17] intel_iommu: fix missing BQL in pt fast path

[Michael S. Tsirkin]

From: Peter Xu <address@hidden>

In vtd_switch_address_space() we did the memory region switch, however
it's possible that the caller of it has not taken the BQL at all. Make
sure we have it.

CC: Paolo Bonzini <address@hidden>
CC: Jason Wang <address@hidden>
CC: Michael S. Tsirkin <address@hidden>
Signed-off-by: Peter Xu <address@hidden>
Reviewed-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
---
 hw/i386/intel_iommu.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index a7bf87a..3a5bb0b 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -957,6 +957,8 @@ static bool vtd_dev_pt_enabled(VTDAddressSpace *as)
 static bool vtd_switch_address_space(VTDAddressSpace *as)
 {
     bool use_iommu;
+    /* Whether we need to take the BQL on our own */
+    bool take_bql = !qemu_mutex_iothread_locked();
 
     assert(as);
 
@@ -967,6 +969,15 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
                                    VTD_PCI_FUNC(as->devfn),
                                    use_iommu);
 
+    /*
+     * It's possible that we reach here without BQL, e.g., when called
+     * from vtd_pt_enable_fast_path(). However the memory APIs need
+     * it. We'd better make sure we have had it already, or, take it.
+     */
+    if (take_bql) {
+        qemu_mutex_lock_iothread();
+    }
+
     /* Turn off first then on the other */
     if (use_iommu) {
         memory_region_set_enabled(&as->sys_alias, false);
@@ -976,6 +987,10 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
         memory_region_set_enabled(&as->sys_alias, true);
     }
 
+    if (take_bql) {
+        qemu_mutex_unlock_iothread();
+    }
+
     return use_iommu;
 }
 
-- 
MST