IOMMU: generalize and correct softirq processing during Dom0 device setup

c/s 21039:95f5a4ce8f24 ("VT-d: reduce default verbosity") having put a
call to process_pending_softirqs() in VT-d's domain_context_mapping()
was wrong in two ways: For one we shouldn't be doing this when setting
up a device during DomU assignment. And then - I didn't check whether
that was the case already back then - we shouldn't call that function
with the pcidevs_lock (or in fact any spin lock) held.

Move the "preemption" into generic code, at once dealing with further
actual (too much output elsewhere - particularly on systems with very
many host bridge like devices - having been observed to still cause the
watchdog to trigger when enabled) and potential (other IOMMU code may
also end up being too verbose) issues.

Do the "preemption" once per device actually being set up when in
verbose mode, and once per bus otherwise.

Note that dropping pcidevs_lock around the process_pending_softirqs()
invocation is specifically not a problem here: We're in an __init
function and aren't racing with potential additions/removals of PCI
devices. Not acquiring the lock in setup_dom0_pci_devices() otoh is not
an option, as there are too many places that assert the lock being
held.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>

diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index c5c8344021c1518fcba1e3a59b8d255c4dad456c..ff78142db585d33548a396b7dfc311c98e625fcf 100644 (file)
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -27,6 +27,7 @@
 #include <xen/delay.h>
 #include <xen/keyhandler.h>
 #include <xen/radix-tree.h>
+#include <xen/softirq.h>
 #include <xen/tasklet.h>
 #include <xsm/xsm.h>
 #include <asm/msi.h>
@@ -922,6 +923,20 @@ static int __init _setup_dom0_pci_devices(struct pci_seg *pseg, void *arg)
                 printk(XENLOG_WARNING "Dom%d owning %04x:%02x:%02x.%u?\n",
                        pdev->domain->domain_id, pseg->nr, bus,
                        PCI_SLOT(devfn), PCI_FUNC(devfn));
+
+            if ( iommu_verbose )
+            {
+                spin_unlock(&pcidevs_lock);
+                process_pending_softirqs();
+                spin_lock(&pcidevs_lock);
+            }
+        }
+
+        if ( !iommu_verbose )
+        {
+            spin_unlock(&pcidevs_lock);
+            process_pending_softirqs();
+            spin_lock(&pcidevs_lock);
         }
     }
 

diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index d5ce5b7bdf837f0d953de0abe108e70385ce85e9..d4be75cf9ca5f5d30e86811d57363aa530644284 100644 (file)
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -31,7 +31,6 @@
 #include <xen/pci.h>
 #include <xen/pci_regs.h>
 #include <xen/keyhandler.h>
-#include <xen/softirq.h>
 #include <asm/msi.h>
 #include <asm/irq.h>
 #include <asm/hvm/vmx/vmx.h>
@@ -1494,9 +1493,6 @@ static int domain_context_mapping(
         break;
     }
 
-    if ( iommu_verbose )
-        process_pending_softirqs();
-
     return ret;
 }