[Xen-devel] [PATCH v4 0/2] Fix xen crash when starting HVM guest due to missing io handler

[<suravee.suthikulpanit@xxxxxxx>]

From: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>

Hi All,

Changes from V3:
  * Remove calls to guest_iommu_init()/destroy() for now since
    the guest iommu feature is not functing and causing breakage. 
  * Do not change the ordering of the iommu_domain_init() and
    hvm_domain_init() for now until we agree on proper ordering.

OVERVIEW:
 
On systems with iommu v2 enabled, the hypervisor crashes when trying
to start up an HVM guest. 

Investigating shows that the guest_iommu_init() is called before the
HVM domain is initialized. It then tries to register_mmio_handler()
causing the hvm_next_io_handler() to increment the io_handler_count.
However, the registration fails silently and left the I/O handler
uninitialized.

At later time, hvm_find_io_handler() is called and iterate through
the registered handlered, but then resulting in referencing NULL
pointers.

This patch series proposes workaround for this issue.

Thanks,
Suravee

Suravee Suthikulpanit (2):
  AMD IOMMU: Removing currently non-functioning guest iommu feature
  x86/hvm: Add check when register io handler

 xen/arch/x86/hvm/intercept.c                | 2 ++
 xen/drivers/passthrough/amd/pci_amd_iommu.c | 4 ----
 2 files changed, 2 insertions(+), 4 deletions(-)

-- 
1.9.1


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