Re: [PATCH 5/6] xen/x86/pvh: Add 32-bit PVH initialization code

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Jul 06, 2015 at 11:34:24PM -0400, Boris Ostrovsky wrote:
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

A little bit more here I think - as in that the parameter
passing is not an Xen specific thing but something this
code cooked up?

> ---
>  arch/x86/xen/enlighten.c |  4 ----
>  arch/x86/xen/smp.c       | 17 ++++++++++-------
>  arch/x86/xen/xen-head.S  | 17 +++++++++++++++--
>  3 files changed, 25 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 7953e68..807337e 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1464,10 +1464,6 @@ static void __init xen_pvh_early_guest_init(void)
>  
>  	xen_pvh_early_cpu_init(0, false);
>  	xen_pvh_set_cr_flags(0);
> -
> -#ifdef CONFIG_X86_32
> -	BUG(); /* PVH: Implement proper support. */
> -#endif
>  }
>  #endif    /* CONFIG_XEN_PVH */
>  
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 7cf0765..99be53b 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -372,11 +372,8 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
>  
>  	gdt = get_cpu_gdt_table(cpu);
>  
> -#ifdef CONFIG_X86_32
> -	/* Note: PVH is not yet supported on x86_32. */
> -	ctxt->user_regs.fs = __KERNEL_PERCPU;
> -	ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
> -#endif
> +	ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
> +	ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
>  
>  	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
>  		ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
> @@ -403,6 +400,8 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
>  		ctxt->kernel_sp = idle->thread.sp0;
>  
>  #ifdef CONFIG_X86_32
> +		ctxt->user_regs.fs = __KERNEL_PERCPU;
> +		ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
>  		ctxt->event_callback_cs     = __KERNEL_CS;
>  		ctxt->failsafe_callback_cs  = __KERNEL_CS;
>  #else
> @@ -424,12 +423,16 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
>  		 */
>  		ctxt->user_regs.eip =
>  			(unsigned long)xen_pvh_early_cpu_init_secondary;
> +#ifdef CONFIG_X86_64
>  		ctxt->user_regs.rdi = cpu;
>  		ctxt->user_regs.rsi = true;  /* entry == true */
> +#else
> +		*((uint32_t *)ctxt->user_regs.esp + 1) = cpu;
> +		*((uint32_t *)ctxt->user_regs.esp + 2) = true;
> +#endif
>  	}
>  #endif
> -	ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
> -	ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
> +
>  	if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
>  		BUG();
>  
> diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
> index b1508a8..12c4e2a 100644
> --- a/arch/x86/xen/xen-head.S
> +++ b/arch/x86/xen/xen-head.S
> @@ -51,14 +51,18 @@ ENTRY(startup_xen)
>  
>  #ifdef CONFIG_XEN_PVH
>  /*
> - * xen_pvh_early_cpu_init() - early PVH VCPU initialization
> + * xen_pvh_early_cpu_init(cpu, entry) - early PVH VCPU initialization
>   * @cpu:   this cpu number (%rdi)
>   * @entry: true if this is a secondary vcpu coming up on this entry
>   *         point, false if this is the boot CPU being initialized for
>   *         the first time (%rsi)

Should this be updated to reflect how it is to be done on 32-bit (as in
not using %rdi and %rsi?)
>   */
>  ENTRY(xen_pvh_early_cpu_init)
> +#ifdef CONFIG_X86_64
>  	mov	%rbx, -8(%rsp)
> +#else
> +	mov	%ebx, -4(%esp)
> +#endif
>  
>  /* Entry point for secondary CPUs */
>  ENTRY(xen_pvh_early_cpu_init_secondary)
> @@ -69,15 +73,24 @@ ENTRY(xen_pvh_early_cpu_init_secondary)
>  
>  	mov     $MSR_EFER, %ecx
>  	rdmsr
> +#ifdef CONFIG_X86_64
>  	bts     $_EFER_SCE, %eax
> +#endif
>  
>  	bt      $20, %ebx
>  	jnc     1f      	/* No NX, skip setting it */
>  	bts     $_EFER_NX, %eax
>  1:	wrmsr
> +
> +#ifdef CONFIG_X86_64
>  	mov	-8(%rsp), %rbx
> -#ifdef CONFIG_SMP
>  	cmp     $0, %esi
> +#else
> +	mov	-4(%esp), %ebx
> +	cmp	$0, 8(%esp)	/* second argument */
> +#endif
> +
> +#ifdef CONFIG_SMP
>  	jne     cpu_bringup_and_idle
>  #endif
>  	ret
> -- 
> 1.8.1.4
>