linux-kernel - Re: [RFC PATCH 2/5] xen/grants: update initialization order of xen grant table

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Date:   Wed, 15 Mar 2023 13:31:14 +0100
From:   Roger Pau Monné <roger.pau@...rix.com>
To:     Huang Rui <ray.huang@....com>
Cc:     Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        Stewart Hildebrand <Stewart.Hildebrand@....com>,
        Xenia Ragiadakou <burzalodowa@...il.com>,
        Honglei Huang <honglei1.huang@....com>,
        Julia Zhang <julia.zhang@....com>,
        Chen Jiqian <Jiqian.Chen@....com>
Subject: Re: [RFC PATCH 2/5] xen/grants: update initialization order of xen
 grant table

On Sun, Mar 12, 2023 at 08:01:54PM +0800, Huang Rui wrote:
> The xen grant table will be initialied before parsing the PCI resources,
> so xen_alloc_unpopulated_pages() ends up using a range from the PCI
> window because Linux hasn't parsed the PCI information yet.
> 
> So modify the initialization order to make sure the real PCI resources
> are parsed before.

Has this been tested on a domU to make sure the late grant table init
doesn't interfere with PV devices getting setup?

> Signed-off-by: Huang Rui <ray.huang@....com>
> ---
>  arch/x86/xen/grant-table.c | 2 +-
>  drivers/xen/grant-table.c  | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
> index 1e681bf62561..64a04d1e70f5 100644
> --- a/arch/x86/xen/grant-table.c
> +++ b/arch/x86/xen/grant-table.c
> @@ -165,5 +165,5 @@ static int __init xen_pvh_gnttab_setup(void)
>  }
>  /* Call it _before_ __gnttab_init as we need to initialize the
>   * xen_auto_xlat_grant_frames first. */
> -core_initcall(xen_pvh_gnttab_setup);
> +fs_initcall_sync();
>  #endif
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index e1ec725c2819..6382112f3473 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -1680,4 +1680,4 @@ static int __gnttab_init(void)
>  }
>  /* Starts after core_initcall so that xen_pvh_gnttab_setup can be called
>   * beforehand to initialize xen_auto_xlat_grant_frames. */

Comment need to be updated, but I was thinking whether it won't be
best to simply call xen_pvh_gnttab_setup() from __gnttab_init() itself
when running as a PVH guest?

Thanks, Roger.