Re: [Xen-devel] [PATCHv9 0/9] Xen: extend kexec hypercall for use with pv-ops kernels

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/10/13 16:26, Daniel Kiper wrote:
> On Tue, Oct 08, 2013 at 05:55:01PM +0100, David Vrabel wrote:
>> The series (for Xen 4.4) improves the kexec hypercall by making Xen
>> responsible for loading and relocating the image.  This allows kexec
>> to be usable by pv-ops kernels and should allow kexec to be usable
>> from a HVM or PVH privileged domain.
> As I can see you taken some sugestions into account. Thanks. But...
> Why did not you send this patch series to kexec@xxxxxxxxxxxxxxxxxxx
> and my Oracle address? Why did not you implemented kexec hypercall
> function to get info about loaded images? Andrew and I asked about that.
> What about setting GPRs to known value (e.g. 0 like in Linux Kernel)
> before jumping into purgatory?

I had forgotten that I had already asked that question (in person) to
David, and that he had answered.

There is no real usecase for such a hypercall, and introduces a
TimeOfCheck-TimeOfUse race condition, as nothing stops the interleaving
of a KEXECOP_unload hypercall.

The KEXECOP_kexec hypercall is well specified in so far as it will
return if an image is not loaded.

~Andrew

>
> By the way, you do not need to save and restore %rdi, %rsi and %rbx
> in relocate_pages() in xen/arch/x86/x86_64/kexec_reloc.S.
>
> Daniel
>
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