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Re: [PATCH RFC 1/6] xen/arm: mm: Remove special case for CPU0 in dump_hyp_walk()
- To: Julien Grall <julien@xxxxxxx>
- From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Date: Tue, 24 Nov 2020 17:10:07 +0000
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- Cc: "open list:X86" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>
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- Thread-topic: [PATCH RFC 1/6] xen/arm: mm: Remove special case for CPU0 in dump_hyp_walk()
Hi Julien,
> On 19 Nov 2020, at 19:07, Julien Grall <julien@xxxxxxx> wrote:
>
> From: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>
> There is no need to have a special case for CPU0 when converting the
> page-table virtual address into a physical address. The helper
> virt_to_maddr() is able to translate any address as long as the root
> page-tables is mapped in the virtual address. This is the case for all
> the CPUs at the moment.
>
> So use the same BUG_ON() regardless the CPU.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> [julien: Rework the commit message]
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
Cheers
Bertrand
>
> ---
>
> I went back through the conversation in [1] regarding the issue when
> loading Xen below 2MB on Arm32. The example provided is wrong because to
> find the physical address, we need to add 'phys_offset', not substract.
>
> So I removed the comment regarding the code was buggy.
>
> [1] https://marc.info/?l=xen-devel&m=157081398022401
> ---
> xen/arch/arm/mm.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 9c4b26bf079b..4dd886f7c80d 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -284,10 +284,7 @@ void dump_hyp_walk(vaddr_t addr)
> "on CPU%d via TTBR 0x%016"PRIx64"\n",
> addr, smp_processor_id(), ttbr);
>
> - if ( smp_processor_id() == 0 )
> - BUG_ON( (lpae_t *)(unsigned long)(ttbr - phys_offset) != pgtable );
> - else
> - BUG_ON( virt_to_maddr(pgtable) != ttbr );
> + BUG_ON( virt_to_maddr(pgtable) != ttbr );
> dump_pt_walk(ttbr, addr, HYP_PT_ROOT_LEVEL, 1);
> }
>
> --
> 2.17.1
>
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