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Re: [PATCH v2 1/3] x86/xen: use clear_bss() for Xen PV guests


  • To: Juergen Gross <jgross@xxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Thu, 23 Jun 2022 11:51:42 +0200
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  • Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
  • Delivery-date: Thu, 23 Jun 2022 09:51:52 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 23.06.2022 11:46, Juergen Gross wrote:
> --- a/arch/x86/xen/enlighten_pv.c
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -1183,15 +1183,19 @@ static void __init xen_domu_set_legacy_features(void)
>  extern void early_xen_iret_patch(void);
>  
>  /* First C function to be called on Xen boot */
> -asmlinkage __visible void __init xen_start_kernel(void)
> +asmlinkage __visible void __init xen_start_kernel(struct start_info *si)
>  {
>       struct physdev_set_iopl set_iopl;
>       unsigned long initrd_start = 0;
>       int rc;
>  
> -     if (!xen_start_info)
> +     if (!si)
>               return;
>  
> +     clear_bss();

As per subsequent observation, this shouldn't really be needed: The
hypervisor (or tool stack for DomU-s) already does so. While I guess
we want to keep it to be on the safe side, maybe worth a comment?

Jan



 


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