Re: [libvirt] [PATCH 3/3] qemu: caps: Advertise arm 32-on-64 KVM option

On Thu, May 21, 2015 at 07:03:28PM -0400, Cole Robinson wrote: > We need to use qemu-system-aarch64 to run armv7l KVM VMs on an aarch64 > host. > --- > src/qemu/qemu_capabilities.c | 42 ++++++++++++++++++++++-------------------- > 1 file changed, 22 insertions(+), 20 deletions(-) > > diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c > index 1e7bddb..7181865 100644 > --- a/src/qemu/qemu_capabilities.c > +++ b/src/qemu/qemu_capabilities.c > @@ -723,19 +723,6 @@ virQEMUCapsFindBinaryForArch(virArch hostarch, > return ret; > } > > - > -static bool > -virQEMUCapsIsValidForKVM(virArch hostarch, > - virArch guestarch) > -{ > - if (hostarch == guestarch) > - return true; > - if (hostarch == VIR_ARCH_X86_64 && > - guestarch == VIR_ARCH_I686) > - return true; > - return false; > -} > - > static int > virQEMUCapsInitGuest(virCapsPtr caps, > virQEMUCapsCachePtr cache, > @@ -747,6 +734,7 @@ virQEMUCapsInitGuest(virCapsPtr caps, > char *binary = NULL; > virQEMUCapsPtr qemubinCaps = NULL; > virQEMUCapsPtr kvmbinCaps = NULL; > + bool native_kvm, x86_32on64_kvm, arm_32on64_kvm; > int ret = -1; > > /* Check for existence of base emulator, or alternate base > @@ -764,16 +752,30 @@ virQEMUCapsInitGuest(virCapsPtr caps, > > /* qemu-kvm/kvm binaries can only be used if > * - host & guest arches match > - * Or > - * - hostarch is x86_64 and guest arch is i686 > - * The latter simply needs "-cpu qemu32" > + * - hostarch is x86_64 and guest arch is i686 (needs -cpu qemu32) > + * - hostarch is aarch64 and guest arch is armv7l (needs -cpu aarch64=off) > */ > - if (virQEMUCapsIsValidForKVM(hostarch, guestarch)) { > - const char *const kvmbins[] = { "/usr/libexec/qemu-kvm", /* RHEL */ > - "qemu-kvm", /* Fedora */ > - "kvm" }; /* Upstream .spec */ > + native_kvm = (hostarch == guestarch); > + x86_32on64_kvm = (hostarch == VIR_ARCH_X86_64 && > + guestarch == VIR_ARCH_I686); > + arm_32on64_kvm = (hostarch == VIR_ARCH_AARCH64 && > + guestarch == VIR_ARCH_ARMV7L); > + > + if (native_kvm || x86_32on64_kvm || arm_32on64_kvm) { > + const char *kvmbins[] = { > + "/usr/libexec/qemu-kvm", /* RHEL */ > + "qemu-kvm", /* Fedora */ > + "kvm", /* Debian/Ubuntu */ > + NULL, > + }; > + > + if (arm_32on64_kvm) > + kvmbins[3] = "qemu-system-aarch64"; I'm unclear why you need to be adding this. We don't need it for the equivalent i686 with qemu-system-x86_64, as the earlier call to virQEMUCapsFindBinaryForArch() will already return the binary qemu-system-x86_64. IIUC, it should have returned the binary qemu-system-aarch64 too, so this just seems to duplicate the check for that binary.