On Mon, Sep 03, 2018 at 03:15:29PM +1000, Paul Mackerras wrote: > On Mon, Sep 03, 2018 at 01:28:44PM +1000, David Gibson wrote: > > On Fri, Aug 31, 2018 at 04:08:50PM +1000, Alexey Kardashevskiy wrote: > > > At the moment the real mode handler of H_PUT_TCE calls iommu_tce_xchg_rm() > > > which in turn reads the old TCE and if it was a valid entry - marks > > > the physical page dirty if it was mapped for writing. Since it is > > > the real mode, realmode_pfn_to_page() is used instead of pfn_to_page() > > > to get the page struct. However SetPageDirty() itself reads the compound > > > page head and returns a virtual address for the head page struct and > > > setting dirty bit for that kills the system. > > > > > > This moves dirty bit setting before updating the hardware table > > > > Um.. but now you're setting DIRTY based on the *new* TCE's > > permissions, instead of the old TCE's permissions, which I don't think > > is correct. > > He's setting dirty on the page which is about to be mapped if the new > TCE allows the page to be written by the device. Given that the page > is pinned, I don't see any reason why the dirty setting has to be done > when the page is unmapped rather than when it is mapped. Do you see a > reason? Hrm. Couldn't the page get marked clean by some other path before it is unmapped in that case? -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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