On 08/04/2015 14:16, Radim Krčmář wrote: > 2015-04-08 12:43+0200, Paolo Bonzini: >> On 08/04/2015 11:26, Radim Krčmář wrote: >>> Only cross-memslot writes have NULL memslot. >> >> The power of wrong comments... >> >> Considering how kvm_gfn_to_hva_cache_init is used (one 1-byte field, two >> 4-byte fields, one 28-bytes struct that is 32-bytes aligned, one >> 32-bytes field that is in practice cacheline-aligned), I wonder if we >> should just use ghc->memslot = NULL for cross page writes. This would >> bypass the bug you are fixing here, and avoid worries about partial writes. > > Good idea, and it could make those comments right :) > (Though in general, I prefer less constraints on APIs ...) It doesn't put constraints, it still handles cross page writes right (just slower). copy_to_user in some sense is the API that constrains us to do this. > Partial writes would be a pain; copy_to_user API does not define which > bytes were not written. I think the write can't fail mid-page, which > makes our implementation ok No, writes can't fail mid-page (I guess in atomic context it's theoretically possible, but we're equipped to handle the failure in that case). Patch applied, thanks! Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
