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Re: [Xen-devel] [v7][RFC][PATCH 08/13] xen/x86/p2m: set p2m_access_n for reserved device memory mapping



On 2014/11/3 18:03, Jan Beulich wrote:
On 03.11.14 at 10:51, <tiejun.chen@xxxxxxxxx> wrote:
On 2014/11/3 17:00, Jan Beulich wrote:
On 03.11.14 at 07:20, <tiejun.chen@xxxxxxxxx> wrote:
#2 the error handling

In an error case what should I do? Currently we still create these
mapping as normal. This means these mfns will be valid so later we can't
set them again then device can't be assigned as passthrough. I think
this makes sense. Or we should just stop them from setting 1:1 mapping?

You should, with very few exceptions, not ignore errors (which
includes "handling" them by just logging a message. Instead, you
should propagate the error back up the call chain.


Do you mean in your patch,

+int iommu_get_reserved_device_memory(iommu_grdm_t *func, void *ctxt)
+{
+    const struct iommu_ops *ops = iommu_get_ops();
+
+    if ( !iommu_enabled || !ops->get_reserved_device_memory )
+        return 0;
+
+    return ops->get_reserved_device_memory(func, ctxt);
+}
+

I shouldn't return that directly. Then instead, we should handle all
error scenarios here?

No. All error scenarios are already being handled here (by
propagating the error code to the caller).

Sorry, how to propagate the error code?

Thanks
Tiejun

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