Re: [Xen-devel] [PATCH FOR-4.5] xen: arm64: Handle memory banks which are not 1GB aligned

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 10/10/2014 03:43 PM, Ian Campbell wrote:
> The code in the arm64 version of setup_xenheap_mappings was making
> some very confused attempts to handle this but was bogus.
> 
> As well as adjusting the mapping to start on a 1GB boundary we also
> need to account for the offset between the start of the mapping and
> the actual start of the heap when converting between page pointers,
> virtual addresses and machine addresses.
> 
> I preferred to do this by explicitly accounting for the offset rather
> than adding an offset to the frametable because that approach could
> potentially waste a large amount of frametable (up to just less than
> 1GB worth) but also because of issues with converting mfns from
> outside the regions considered for pdx initialisation (which are not
> 1GB aligned) back and forth.
> 
> We already have an idea of the distinction between the start of the
> direct map and the start of the xenheap in the difference between
> DIRECTMAP_VIRT_START and XENHEAP_VIRT_START. Until now these were the
> same thing, but now we change XENHEAP_VIRT_START to point to the
> actual start of heap not the mapping. Surprisingly there was only one
> place which was using the conceptually wrong value.
> 
> Also change xenheap_virt_end to a vaddr_t for consistency.
> 
> We've been lucky so far that most hardware happens to locate memory
> on a 1GB boundary (we did have reports of a system with memory at a
> half gig boundary which exhibited failures which I didn't manage to
> follow up on successfully). The EFI support has exposed this
> shortcoming by the way it handles reserved memory, which has a
> similar effect to having memory non-1GB aligned.
> 
> arm32 does things differently here due to using a small Xen heap and
> a demand mapped domain heap, so isn't affected.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Suravee Suthikulanit <suravee.suthikulpanit@xxxxxxx>
> Cc: Roy Franz <roy.franz@xxxxxxxxxx>
> Cc: Vijay Kilari <vijay.kilari@xxxxxxxxx>
> ---
> FOR-4.5: This is a bug fix.

Looks good to me:

Reviewed-by: Julien Grall <julien.grall@xxxxxxxxxx>

Regards,

-- 
Julien Grall

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