Re: [PATCH v13 11/19] xen/pvh: Secondary VCPU bringup (non-bootup CPUs)

[David Vrabel <david.vrabel@citrix.com>]

On 03/01/14 19:38, Konrad Rzeszutek Wilk wrote:
> From: Mukesh Rathor <mukesh.rathor@oracle.com>
> 
> The VCPU bringup protocol follows the PV with certain twists.
> From xen/include/public/arch-x86/xen.h:
> 
> Also note that when calling DOMCTL_setvcpucontext and VCPU_initialise
> for HVM and PVH guests, not all information in this structure is updated:
> 
>  - For HVM guests, the structures read include: fpu_ctxt (if
>  VGCT_I387_VALID is set), flags, user_regs, debugreg[*]
> 
>  - PVH guests are the same as HVM guests, but additionally use ctrlreg[3] to
>  set cr3. All other fields not used should be set to 0.
> 
> This is what we do. We piggyback on the 'xen_setup_gdt' - but modify
> a bit - we need to call 'load_percpu_segment' so that 'switch_to_new_gdt'
> can load per-cpu data-structures. It has no effect on the VCPU0.
> 
> We also piggyback on the %rdi register to pass in the CPU number - so
> that when we bootup a new CPU, the cpu_bringup_and_idle will have
> passed as the first parameter the CPU number (via %rdi for 64-bit).
[...]
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1409,14 +1409,19 @@ static void __init xen_boot_params_init_edd(void)
>   * Set up the GDT and segment registers for -fstack-protector.  Until
>   * we do this, we have to be careful not to call any stack-protected
>   * function, which is most of the kernel.
> + *
> + * Note, that it is refok - because the only caller of this after init

"Note, this is __ref because..."

David