Messages in this thread | | | Date | Thu, 13 Jun 2013 13:47:48 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86: Fix /proc/mtrr with base/size more than 44bits |
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On 06/13/2013 11:53 AM, Yinghai Lu wrote: > > - if (base & size_or_mask || size & size_or_mask) { > + if (base >> (boot_cpu_data.x86_phys_bits - PAGE_SHIFT) || > + base > (base + size) || > + (base + size - 1) >> (boot_cpu_data.x86_phys_bits - PAGE_SHIFT)) { > pr_warning("mtrr: base or size exceeds the MTRR width\n"); > return -EINVAL; > }
Most of this patch looks good as far as being a minimal patch, but I'm really confused about this bit. Could you explain the reason for why the original doesn't work? (To be fair: I am not even sure the original does anything useful so it could just be a "this is just too broken to live" kind of thing.)
The first and third clause of the test can be simplified, however:
(base | (base + size - 1)) >> (boot_cpu_data.x86_phys_bits - PAGE_SHIFT)
... although it would be cleaner to put boot_cpu_data.x86_phys_bits - PAGE_SHIFT into a variable.
A lot of the mask_hi/mask_lo stuff should just get removed by using rdmsrl/wrmsrl, but that is not stable material obviously.
-hpa
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