[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] amd-iommu: get rid of pointless IOMMU_PAGING_MODE_LEVEL_X definitions
> -----Original Message----- > From: Woods, Brian [mailto:Brian.Woods@xxxxxxx] > Sent: 12 October 2018 18:14 > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Suthikulpanit, Suravee > <Suravee.Suthikulpanit@xxxxxxx>; Woods, Brian <Brian.Woods@xxxxxxx> > Subject: Re: [PATCH] amd-iommu: get rid of pointless > IOMMU_PAGING_MODE_LEVEL_X definitions > > On Thu, Sep 27, 2018 at 01:46:01PM +0100, Paul Durrant wrote: > > The levels are absolute numbers such that IOMMU_PAGING_MODE_LEVEL_X > > evaluates to X (for the valid range of 0 - 7) so simply use numbers in > > the code. > > > > No functional change. > > > > NOTE: This patch also adds emacs boilerplate to amd-iommu-defs.h > > > > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx> > > Is there a strong reason to get rid of these? Some of examples below > create seemingly magic numbers in the code. While if you're familiar > with the functions this isn't a big deal, otherwise you have to dig > further to tell. > The numbers aren't magic though. The spec refers to levels by number rather than any sort of name. If the levels were named then it would be absolutely right to #define <level name> <level number>, but that is not the case. Thus IMO getting rid of the definitions actually makes the code clearer for those (like myself) reading the spec. > > + pte = table + pfn_to_pde_idx(gfn, 1); > > > + need_flush = set_iommu_pde_present(pde, next_mfn, 0, iw, ir); > > If there's a general consensus that getting rid of these is better, I > don't mind and will agree to it. > Anyone else care to comment? Paul > -- > Brian Woods _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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