Messages in this thread | | | Date | Tue, 3 Dec 2013 16:00:18 +0000 | From | One Thousand Gnomes <> | Subject | Re: [PATCH v2] xen/block: Correctly define structures in public headers on ARM32 and ARM64 |
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On Tue, 3 Dec 2013 15:40:37 +0000 Julien Grall <julien.grall@linaro.org> wrote:
> On ARM (32 bits and 64 bits), the double-word is 8-bytes aligned. This will > result on different structure from Xen and Linux repositories. > > As Linux is using __packed__ attribute, it must have a 4-bytes padding before > each "id" field. > > This change breaks guest block support with older kernel. IMHO, it's acceptable > because Xen on ARM is still on Tech Preview and the hypercall ABI is not yet > freezed.
How does a guest ascertain which API to use ?
How does the patch ensure new kernels on existing hypervisor versions don't break ?
What is the failure case given the alignment change seems potentially to produce valid but incorrect I/O requests - can it cause corruption ?
It seems to me you should be defining
struct blkif_request_rw_v2
and using the correct version according to which API the hypervisor requires, not just breaking it.
Alan
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