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Re: [PATCH] pdx: cast PAGE_SIZE value ahead of shifting
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 14 Aug 2025 09:18:45 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 14 Aug 2025 07:18:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 13.08.2025 14:55, Roger Pau Monne wrote:
> --- a/xen/common/pdx.c
> +++ b/xen/common/pdx.c
> @@ -288,7 +288,7 @@ bool __init pfn_pdx_compression_setup(paddr_t base)
>
> pfn_pdx_hole_shift = hole_shift;
> pfn_pdx_bottom_mask = (1UL << bottom_shift) - 1;
> - ma_va_bottom_mask = (PAGE_SIZE << bottom_shift) - 1;
> + ma_va_bottom_mask = ((paddr_t)PAGE_SIZE << bottom_shift) - 1;
Given
#define PAGE_SIZE (_AC(1,L) << PAGE_SHIFT)
this shouldn't be needed, except maybe for Arm32. There, however, ...
> pfn_hole_mask = ((1UL << hole_shift) - 1) << bottom_shift;
... this and the shift immediately ahead would also be a problem afaict,
which makes me conclude this isn't what Coverity has looked at. I expect
the problem is with the toolstack side definition of PAGE_SIZE, which imo
would rather be addressed there. (And yes, I'm pretty averse to arbitrary
casts like this being introduced.)
Jan
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