Re: [Xen-devel] [PATCH v1 5/8]: PVH smp changes

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 21 Sep 2012, Mukesh Rathor wrote:
> ---
>  arch/x86/xen/smp.c |   75 
> ++++++++++++++++++++++++++++++++++------------------
>  1 files changed, 49 insertions(+), 26 deletions(-)
> 
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index f58dca7..e1e8582 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -68,9 +68,11 @@ static void __cpuinit cpu_bringup(void)
>       touch_softlockup_watchdog();
>       preempt_disable();
>  
> -     xen_enable_sysenter();
> -     xen_enable_syscall();
> -
> +     /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
> +     if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
> +             xen_enable_sysenter();
> +             xen_enable_syscall();
> +     }
>       cpu = smp_processor_id();
>       smp_store_cpu_info(cpu);
>       cpu_data(cpu).x86_max_cores = 1;
> @@ -230,10 +232,11 @@ static void __init xen_smp_prepare_boot_cpu(void)
>       BUG_ON(smp_processor_id() != 0);
>       native_smp_prepare_boot_cpu();
>  
> -     /* We've switched to the "real" per-cpu gdt, so make sure the
> -        old memory can be recycled */
> -     make_lowmem_page_readwrite(xen_initial_gdt);
> -
> +     if (!xen_feature(XENFEAT_writable_page_tables)) {
> +             /* We've switched to the "real" per-cpu gdt, so make sure the
> +              * old memory can be recycled */
> +             make_lowmem_page_readwrite(xen_initial_gdt);
> +     }

it is worth adding a comment saying that PVH doesn't need this even if
the pagetable are writable in that case


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