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Re: [Xen-devel] [patch] make evtchn_upcall_pending arch-specific type

To: Hollis Blanchard <hollisb@xxxxxxxxxx>
Subject: Re: [Xen-devel] [patch] make evtchn_upcall_pending arch-specific type
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 31 Mar 2006 13:46:28 +0100
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On 30 Mar 2006, at 20:13, Hollis Blanchard wrote:

evtchn_upcall_pending is another variable that bitops are used on, so PowerPC wants it to be a long. Unfortunately, it's also part of the guest/hypervisor interface, so we can't change it for architectures with existing guests.

Compile-tested on x86(-32). Please apply.

Before going down this route, what about just casting the field to long, since it is actually aligned on a suitable boundary, as it happens? And what will your solution be for fields in grant_entry structure? That's another one where the fields to be atomically updated are at least 8-byte aligned, and where using longer types will bloat a structure that we'd prefer to pack nicely.

If this is the best way for ppc then I think atomic_bit_t would be a nicer typedef.

 -- Keir


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