Messages in this thread | | | Date | Thu, 13 Nov 2014 09:57:38 +0000 | From | "Jan Beulich" <> | Subject | Re: [Xen-devel] [PATCH 3/3] x86/xen: use the maximum MFN to calculate the required DMA mask |
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>>> On 12.11.14 at 16:55, <JBeulich@suse.com> wrote: >>>> On 12.11.14 at 16:25, <david.vrabel@citrix.com> wrote: >> +u64 >> +xen_swiotlb_get_required_mask(struct device *dev) >> +{ >> + u64 max_mfn; >> + >> + max_mfn = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL); >> + >> + return DMA_BIT_MASK(fls64(max_mfn << PAGE_SHIFT) + 1); >> +} > > The value the hypercall returns is exclusive and an unsigned long.
The latter has further relevance: For one, HYPERVISOR_memory_op() returns "int" currently - this needs to become "long" for the purpose here (also for eventual future uses of XENMEM_maximum_gpfn and XENMEM_{current,maximum}_reservation).
And then, using u64 rather than unsigned long for max_mfn would still cause problems for 32-bit kernels on systems with memory extending beyond the 8Tb boundary (since the long -> u64 conversion really goes long -> s64 -> u64).
Jan
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