On 05/28/2015 07:31 AM, Daniel P. Berrange wrote:
> 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.
We need this in the case you are running on an aarch64 host and have both
qemu-system-arm and qemu-system-aarch64 installed. In this case, when you want
to use KVM for arm32, you _have_ to use qemu-system-aarch64, qemu-system-arm
does not work. What you suggest would mean that qemu-system-arm is grabbed
from the caps cache.
x86 doesn't have this problem because qemu-system-i386, qemu-system-x86_64 and
by extension qemu-kvm can all be used to do 32-on-64 KVM.
Thanks,
Cole
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