On Thu, 4 Mar 2021 09:10:44 +0100 David Hildenbrand <da...@redhat.com> wrote:
> On 03.03.21 22:36, Richard Henderson wrote: > > On 3/3/21 1:22 PM, David Hildenbrand wrote: > >> > >>> Am 03.03.2021 um 22:19 schrieb Richard Henderson > >>> <richard.hender...@linaro.org>: > >>> > >>> On 3/3/21 1:11 PM, David Hildenbrand wrote: > >>>> MMIO on s390x? :) > >>> > >>> hw/s390x/s390-pci-bus.c, memory_region_init_io*(). > >>> > >> > >> ... part of system address space where a CPU could stumble over it? > > > > Impossible to tell within 3 layers of object wrappers. :-( > > I suppose I have no idea how "pci" was hacked onto s390x. > > You've used the right words to describe "pci" (!) on s390x. > > IIRC, there is no MMIO: configuration space accesses etc. are performed > using special access instructions - which will "emulate" the MMIO access > performed on other archs via simple read/write instructions. Yes, it's all specialized instructions. (QEMU emulates one set, there's a newer one supported by the Linux kernel that is a bit more mmio-like in semantics, but I don't know the details.) > > Ordinary instructions (e.g., mvpg) that operate on the system address > space should never stumble over MMIO regions - because that concept does > not exist on s390x. > That's my understanding as well.
