Re: [PATCH] xen: arm: remove hardcoded gnttab location from dom0

[Julien Grall <julien.grall@linaro.org>]

On 12/03/2013 03:04 PM, Ian Campbell wrote:
> The DT provided to guests (including dom0) includes a Xen node which, among
> other things, describes an MMIO region which can be safely used for grant
> table mappings (i.e. it is a hole in the physical address space). For domU we
> provide a hardcoded values based on our hardcoded guest virtual machine
> layout. However for dom0 we need to fit in with the underlying platform.
> Leaving this hardcoded was an oversight which on some platforms could result
> in the grant table overlaying RAM or MMIO regions which are in use by domain
> 0.
> 
> For the 4.4 release do as we did with the dom0 evtchn PPI and provide a hook
> for the platform code to supply a suitable hardcoded address for the platform
> (derived from reading the data sheet). Platforms which do not provide the hook
> get the existing address as a default.
> 
> After 4.4 we should switch to selecting a region of host RAM which is not RAM
> in the guest address map. This should be more flexible and safer but the patch
> was looking too complex for 4.4.
> 
> Platform        Gnttab Address
> ========        ==============
> exynos5.c       0xb0000000, confirmed with Julien.
> sunxi.c         0x01d00000, confirmed in data sheet.
> midway.c        0xff800000, confirmed with Andre, boot tested.
> vexpress.c      0xb0000000, existing hardcoded value was selected for vexpress.
> omap5.c         0xb0000000, no datasheet, looks safe in DTB.
> xgene-storm.c   0x1f800000, reserved according to datasheet, boot tested.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Cc: Julien.Grall@linaro.org
> Cc: Stefano.Stabellini@eu.citrix.com
> Cc: Andre Przywara <andre.przywara@linaro.org>
> Cc: Chen Baozi <baozich@gmail.com>
> Cc: Pranavkumar Sawargaonkar <psawargaonkar@apm.com>
> Cc: Anup Patel <apatel@apm.com>
> ---
>  xen/arch/arm/domain_build.c          |    7 +++++--
>  xen/arch/arm/platform.c              |   14 ++++++++++++++
>  xen/arch/arm/platforms/midway.c      |    3 +++
>  xen/arch/arm/platforms/sunxi.c       |    3 +++
>  xen/arch/arm/platforms/xgene-storm.c |    3 +++
>  xen/include/asm-arm/platform.h       |    7 +++++++
>  6 files changed, 35 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index be39686..332e937 100644
>  
>  /*
> diff --git a/xen/include/asm-arm/platform.h b/xen/include/asm-arm/platform.h
> index 5900ee4..bda4e41 100644
> --- a/xen/include/asm-arm/platform.h
> +++ b/xen/include/asm-arm/platform.h
> @@ -41,6 +41,12 @@ struct platform_desc {
>       * The IRQ (PPI) to use to inject event channels to dom0.
>       */
>      unsigned int dom0_evtchn_ppi;
> +    /*
> +     * The location of a region of physical address space which dom0
> +     * can use for grant table mappings. If size is zero defaults to
> +     * 0xb0000000-0xb0020000.
> +     */
> +    paddr_t dom0_gnttab_start, dom0_gnttab_size;

The size looks the same everywhere, can we just hardcode the base
address per platform?

-- 
Julien Grall