Re: [Xen-devel] [PATCH v2 3/3] tools/libxc: retry hypercall in case of EFAULT

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

Juergen Gross writes ("[PATCH v2 3/3] tools/libxc: retry hypercall in case of 
EFAULT"):
> A hypercall issued via the privcmd driver can very rarely return
> -EFAULT even if the hypercall buffers are locked in memory. This
> happens for hypercall buffers in user memory when the Linux kernel
> is doing memory scans e.g. for page migration or compaction.
> 
> Retry the getpageframeinfo3 hypercall up to 2 times in case
> -EFAULT is returned and the hypervisor might see invalid PTEs for
> user hypercall buffers (which should be the case only if the kernel
> doesn't offer a /dev/xen/hypercall node).
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

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