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SubjectRe: [PATCH] x86_64,xen,espfix: Initialize espfix on secondary CPUs
On Tue, Jul 15, 2014 at 08:26:41AM -0700, Andy Lutomirski wrote:
> Xen doesn't call start_secondary.

Duh!
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
> ---
>
> espfix still doesn't seem to work on Xen (it goes boom in some way that
> I don't understand right now), but initializing all CPUs instead of just
> one of them seems like a good start.
>
> ISTM the right fix is probably to shove the espfix logic into
> native_iret and to tweak the paravirt logic so that native_iret always
> gets invoked. I suspect that Xen will need its own implementation of
> espfix64 in the hypervisor and that, ultimately, someone may want to
> stop initializing espfix64 at all on Xen guests.

I think just disallowing would be preferrable.

Thanks for posting this patch!
>
> arch/x86/xen/smp.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 7005974..eea9bcc 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -23,6 +23,7 @@
> #include <asm/desc.h>
> #include <asm/pgtable.h>
> #include <asm/cpu.h>
> +#include <asm/espfix.h>
>
> #include <xen/interface/xen.h>
> #include <xen/interface/vcpu.h>
> @@ -85,6 +86,13 @@ static void cpu_bringup(void)
>
> xen_setup_cpu_clockevents();
>
> + /*
> + * Enable the espfix hack for this CPU
> + */
> +#ifdef CONFIG_X86_ESPFIX64
> + init_espfix_ap();
> +#endif
> +
> notify_cpu_starting(cpu);
>
> set_cpu_online(cpu, true);
> --
> 1.9.3
>


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