Re: [Xen-devel] [PATCH 8/9] x86/hypercall: Merge the hypercall arg tables

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 03/08/16 16:12, Jan Beulich wrote:
>>>> On 18.07.16 at 11:51, <andrew.cooper3@xxxxxxxxxx> wrote:
>> For the same reason as c/s 33a231e3f "x86/HVM: fold hypercall tables" and
>> (TODO - changeset) "x86/pv: Merge the pv hypercall tables", this removes the
>> risk of accidentally updating only one of the tables.
> Based on this argument perhaps hypercall and args tables should
> get folded too, but I guess that's a work item for another day.

That is rather harder to do.  I thought about it, but couldn't find a
neat way of doing it.

The call table is an array of pointers, while the args table is an array
of bytes.  Merging them would result in excessive padding for alignment
purposes, unless it was packed, at which point we are calling
non-aligned function pointers, and taking that associated performance hit.

~Andrew

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