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Re: [Xen-devel] [PATCH] amd iommu: disable iommu emulation on non-iommu systems

On 02/01/2012 04:58 PM, Jan Beulich wrote:
On 26.01.12 at 11:56, Wei Wang<wei.wang2@xxxxxxx>  wrote:
--- a/xen/drivers/passthrough/amd/iommu_guest.c Tue Jan 24 16:46:17 2012 +0000
+++ b/xen/drivers/passthrough/amd/iommu_guest.c Thu Jan 26 11:50:02 2012 +0100
@@ -805,6 +805,9 @@ int guest_iommu_set_base(struct domain *
     p2m_type_t t;
     struct guest_iommu *iommu = domain_iommu(d);

+    if ( !is_hvm_domain(d) || !iommu_enabled || !iommuv2_enabled )
+        return 0;

Is it really appropriate/correct to return 0 here, while ...

good point, will be fixed in the next try. No one use guest_iommu_set_base so far until remaining patches got committed.

     if ( !iommu )
         return -EACCES;

... here it is -EACCES? Further, are the extra checks needed at all
(i.e. wouldn't domain_iommu() return NULL in all of these cases
anyway due to the same checks being added to guest_iommu_init())?
If so, the checks you add to guest_iommu_destroy() are pointless

It is just to make sure those functions are not called by an unexpected code path since it is non-static. But I can remove it if you prefer that.



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