[Qemu-devel] spapr_pci.c:spapr_pci_msi_init() creates memory region whose size is host-dependent

[Peter Maydell]

spapr_pci_msi_init() does this:

    memory_region_init_io(&spapr->msiwindow, NULL, &spapr_msi_ops, spapr,
                          "msi", getpagesize());

That means this device's memory region size will depend on
the host OS CPU and configuration, which seems like a bad idea,
especially if this machine is supposed to work with TCG.
It also means that on Win32 the compiler complains:

  CC    ppc64-softmmu/hw/ppc/spapr_pci.o
cc1: warnings being treated as errors
/home/petmay01/linaro/qemu-from-laptop/qemu/hw/ppc/spapr_pci.c: In
function ‘spapr_pci_msi_init’:
/home/petmay01/linaro/qemu-from-laptop/qemu/hw/ppc/spapr_pci.c:482:
warning: implicit declaration of function ‘getpagesize’
/home/petmay01/linaro/qemu-from-laptop/qemu/hw/ppc/spapr_pci.c:482:
warning: nested extern declaration of ‘getpagesize’

since getpagesize() doesn't exist there.

Not sure which of the following is best:
 * use a fixed size for the memory region (eg "worst
   case page size for target CPU")
 * query the target CPU for its page size rather than the
   host OS/CPU
 * guard with suitable ifdefs if this code can't actually
   be used except with KVM
 * abstract out the "how do I find my page size on $OS?"
   check to an os-*.c file
 * something else

Any suggestions?

It would be nice to fix this because I think this is the last
Win32 compiler warning.

thanks
-- PMM