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

[Quan Xu <quan.xu@xxxxxxxxx>]

Doing what we do serves as a fix for a bug found in AMD IOMMU initialization.

The current code is using spin_lock{_irqsave(), _irqrestore()} to
protect pci_get_dev() in the set_iommu_interrupt_handler(). However,
this can only be called during AMD IOMMU initialization, with interrupt
enabled, so at least it is not necessary to disable interrupts, or
save/restore interrupt flag.

In order to fix this, we can use just plain spin{_lock(),_unlock()},
instead of spin_lock{_irqsave(),_irqrestore()}.

Signed-off-by: Quan Xu <quan.xu@xxxxxxxxx>
CC: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
CC: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@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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