Re: [Xen-devel] [PATCH v2 01/18] x86/traps: factor out pv_percpu_traps_init

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 05/05/17 15:48, Wei Liu wrote:
> The body of subarch_percpu_traps_init is for setting up PV syscall
> trampoline. Move that into a dedicated function.
>
> Leave the BUILD_BUG_ON in the original function as it is not tied to PV.
>
> No functional change.
>
> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>

The trampolines are only intended to be used by PV guests, but are still
constitute parts of Xen setting up its entrypoints in a safe manor.

At the time I was adjusting the MSR_CSTAR handling, it was decided to
retain it pointing at a safe location, even on hardware which shouldn't
be able to use it.

Therefore, my plan was to keep the trampolines as general x86
infrastructure, and have the (lifted into C) syscall entry points gain
something like BUG_ON(!IS_DEFINED(CONFIG_PV))

~Andrew

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