[Xen-devel] [PATCH v3 1/2] IOMMU/spinlock: Fix a bug found in AMD IOMMU initialization

[Quan Xu <quan.xu@xxxxxxxxx>]

pcidevs_lock should be held with interrupt enabled. However there remains
an exception in AMD IOMMU code, where the lock is acquired with interrupt
disabled. This inconsistency might lead to deadlock.

The fix is straightforward to use spin_lock instead. Also interrupt has been
enabled when this function is invoked, so we're sure consistency around
pcidevs_lock can be guaranteed after this fix.

Signed-off-by: Quan Xu <quan.xu@xxxxxxxxx>
Reviewed-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
CC: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
CC: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/drivers/passthrough/amd/iommu_init.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/passthrough/amd/iommu_init.c 
b/xen/drivers/passthrough/amd/iommu_init.c
index d90a2d2..a400497 100644
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -778,7 +778,6 @@ static bool_t __init set_iommu_interrupt_handler(struct 
amd_iommu *iommu)
 {
     int irq, ret;
     hw_irq_controller *handler;
-    unsigned long flags;
     u16 control;
 
     irq = create_irq(NUMA_NO_NODE);
@@ -788,10 +787,10 @@ static bool_t __init set_iommu_interrupt_handler(struct 
amd_iommu *iommu)
         return 0;
     }
 
-    spin_lock_irqsave(&pcidevs_lock, flags);
+    spin_lock(&pcidevs_lock);
     iommu->msi.dev = pci_get_pdev(iommu->seg, PCI_BUS(iommu->bdf),
                                   PCI_DEVFN2(iommu->bdf));
-    spin_unlock_irqrestore(&pcidevs_lock, flags);
+    spin_unlock(&pcidevs_lock);
     if ( !iommu->msi.dev )
     {
         AMD_IOMMU_DEBUG("IOMMU: no pdev for %04x:%02x:%02x.%u\n",
-- 
1.9.1


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