On 04/26/18 17:51, Markus Armbruster wrote: > Eric Blake <ebl...@redhat.com> writes: > >> On 04/26/2018 09:34 AM, Markus Armbruster wrote: >>>> >>>> Acerbic discovery of the day: @CpuInfoArch has "x86", while configure >>>> produces: >>>> >>>> TARGET_NAME TARGET_BASE_ARCH >>>> i386 i386 >>>> x86_64 i386 >>>> >>>> Note how "i386" does not match "x86". >>> >>> Review fail. >>> >>> Just three weeks ago, we could still have fixed query-cpus-fast... >> >> Actually, I think we still can. We already documented in the 2.12 >> release notes that the "arch" field of query-cpus-fast is known to be >> broken for all but "s390x" (which is really the only arch field that >> MUST be correct, as that is the only time we send additional >> information). And introspection can easily see both the enum contents >> (if we add something) as well as any other additions to the >> query-cpus-fast output union (although that is less likely), to use >> those as a witness for whether qemu is new enough to have fixed the >> bogus "arch" values. I'd argue that if we change things right now, with >> intent to include the change in 2.12.1, before people start relying on >> the bogus "arch" of 2.12, then we should feel free to make >> query-cpus-fast output whatever we want for all architectures other than >> "s390x", even if it changes the current output of "x86". > > In other words, we managed to screw up query-cpus-fast sufficiently to > let us fix it even now. Cool, let's do it! >
Let me clarify a little. The @CpuInfoArch enum has the following constants now: ['x86', 'sparc', 'ppc', 'mips', 'tricore', 's390', 'riscv', 'other' ] This enum was originally introduced in 2.6 (according to the documentation), and only the @s390 and @riscv constants were added in 2.12. The enum constants show up in the following two places, *on the wire*: - in @CpuInfo.@arch, only produced by @query-cpus, - in @CpuInfoFast.@arch, only produced by @query-cpus-fast. The plan would be to rewrite *all* those enum constants of @CpuInfoArch to which the respective TARGET_BASE_ARCH values (from "configure") do not map *identically*. Here's the mapping: TARGET_BASE_ARCH CpuInfoArch CpuInfoArch needs change ---------------- ----------- ------------------------ i386 x86 YES sparc sparc no ppc ppc no mips mips no tricore tricore no s390x s390 YES riscv riscv no In other words, @CpuInfoArch would have to be changed to the following: ['i386', 'sparc', 'ppc', 'mips', 'tricore', 's390x', 'riscv', 'other' ] ^^^^^^ ^^^^^^^ This means that the @arch field, returned by @query-cpus and @query-cpus-fast, would change incompatibly for those QAPI clients that look specifically for "x86" or "s390". Is this a safe change? I would say, because of the 's390' -> 's390x' change, that it isn't. (Also, to confirm, the wiki section at <https://wiki.qemu.org/Planning/2.12#Issues_that_will_not_be_fixed> states, * the query-cpus-fast QMP command reports bogus arch data for all architectures except x86 and s390; applications should be careful to not rely on the bogus information It (correctly) refers to "s390". That value would change.) Thanks Laszlo
