Messages in this thread |  | | Date | Wed, 12 Nov 2014 16:59:10 +0000 | From | David Vrabel <> | 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 15:55, Jan Beulich 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 docs in include/public/memory.h say:
"Returns the maximum machine frame number of mapped RAM in this system."
Which sounds inclusive to me... Do we need a doc update here?
> Hence I'd suggest > > u64 > xen_swiotlb_get_required_mask(struct device *dev) > { > unsigned long max_mfn; > > max_mfn = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL); > > return DMA_BIT_MASK(__fls(max_mfn - 1) + 1 + PAGE_SHIFT); > } > > Jan >
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