On Thu, 8 Oct 2015, Ian Campbell wrote: > On Wed, 2015-10-07 at 19:16 +0100, Julien Grall wrote: > > > Furthermore, based on the spec (4.3.12 in IHI 0048B.b): "A register > > field corresponding to an unimplemented interrupt is RAZ/WI." > > > > If the user knows that an interrupt is not implemented, he may decide to > > write 0 in the corresponding byte. With the current solution, the whole > > write access is ignored. > > > > The solution suggested in this patch is less restrictive and will just > > ignore the corresponding byte if it's 0. > > I think this (a 32-bit register covering both implemented and non > -implemented interrupts) is a compelling reason to only ignore the specific > zero bytes and not the whole word.
I agree that zero writes to unimplemented interrupts should be allowed. However allowing them for everything encourages 32-bit writes with just one byte set, the one that the OS actually wants to write. It doesn't seem correct to me. Something like: uint32_t val = 0x2 << 8; write32(ITARGETSR + something, val); which I don't think is supposed to work. That said, I recognize that this is a minor issue, so I won't insist. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
