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Re: [Xen-devel] [PATCH 0/5] x86: properly propagate errors to hypercall

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0/5] x86: properly propagate errors to hypercall callee
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Fri, 11 Mar 2011 12:33:27 +0000
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH 0/5] x86: properly propagate errors to hypercall callee
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On 11/03/2011 10:44, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

> ioremap() in general can fail, but failure of the writing the page
> table entries gets propagated to the caller only on the legacy
> kernels iirc (due to the lack of a return value of the accessor for
> pv-ops).
> The problem at hand, however, is with the vm_insert_...()
> functions, which use set_pte_at(), which again has no return
> value, so it'll need to be the accessors themselves to
> (a) never utilize the writeable page tables feature on any path
> that can alter cache attributes, and
> (b) handle -ENOMEM from HYPERVISOR_update_va_mapping()
> and HYPERVISOR_mmu_update() (without knowing much about
> the context they're being called in).

I can't see changes like that getting upstream. Maybe okay if you're
prepared to carry the patch. Also I guess some callers may have trouble
handling the error no matter how far you punt it up the call chain.

 -- Keir

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