Re: [Xen-devel] [PATCH 04/17] xen: arm: support building a 64-bit dom0 domain

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 30 July 2013 10:34, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Mon, 2013-07-29 at 19:29 +0100, Julien Grall wrote:
>> On 07/29/2013 01:20 PM, Ian Campbell wrote:
>> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
>> > Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>>
>> My apologies, I didn't give a try of this patch series until now.
>> This patch breaks DOM0 boot on the Arndale Board.
>
> No need to apologise, this was entirely my fault: I had dom0_vcpus=1 in
> my command line and didn't realise/had forgotten.
>
>> > @@ -598,6 +596,11 @@ int construct_dom0(struct domain *d)
>> >
>> >      if ( is_pv32_domain(d) )
>> >      {
>> > +        regs->cpsr = PSR_GUEST_INIT|PSR_MODE_SVC;
>> > +
>> > +        /* Pretend to be a Cortex A15 */
>> > +        d->arch.vpidr = 0x410fc0f0;
>>
>> It's not related to the bug. But why do you fake the VPIDR for each
>> 32-bits guest even on real 32-bits hardware?
>
> That's a total brainfart on my part.
>
> Actually I think it is pretty bogus even for 32-bit guests on 64-bit
> hardware, there is no reason to lie about the underlying CPU if it
> supports AArch32 EL1 (which it must, or we wouldn't be running the
> kernel). All this lie will do is confuse the kernel into applying the
> wrong set of errata etc.
>
> 8<------------------------
>
> From 7292558249ad3da666adb32c5fbe10618a309957 Mon Sep 17 00:00:00 2001
> From: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Date: Tue, 30 Jul 2013 09:42:06 +0100
> Subject: [PATCH] xen: arm: do not pretend to be a Cortex-A15 when running 
> 32-bit guests
>
> It is definitely wrong to do this when running on 32-bit hardware but even
> when running on 64-bit hardware it's not really necessary and may cause more
> harm than good if the underlying processor is not all that similar to an A15.
>
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>  xen/arch/arm/domain_build.c |    3 ---
>  1 files changed, 0 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index a9292e6..582eeae 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -604,9 +604,6 @@ int construct_dom0(struct domain *d)
>      {
>          regs->cpsr = PSR_GUEST32_INIT;
>
> -        /* Pretend to be a Cortex A15 */
> -        d->arch.vpidr = 0x410fc0f0;
> -
>          /* FROM LINUX head.S
>           *
>           * Kernel startup entry point.
> --
> 1.7.2.5
>
>
>



-- 
Julien Grall

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