On 05/29/2013 02:32 AM, Scott Wood wrote: > On 05/24/2013 09:45:24 PM, David Gibson wrote: >> On Wed, May 22, 2013 at 04:06:57PM -0500, Scott Wood wrote: >> > On 05/20/2013 10:06:46 PM, Alexey Kardashevskiy wrote: >> > >diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c >> > >index 8465c2a..da6bf61 100644 >> > >--- a/arch/powerpc/kvm/powerpc.c >> > >@@ -396,6 +396,7 @@ int kvm_dev_ioctl_check_extension(long ext) >> > >+++ b/arch/powerpc/kvm/powerpc.c >> > > break; >> > > #endif >> > > case KVM_CAP_SPAPR_MULTITCE: >> > >+ case KVM_CAP_SPAPR_TCE_IOMMU: >> > > r = 1; >> > > break; >> > > default: >> > >> > Don't advertise SPAPR capabilities if it's not book3s -- and >> > probably there's some additional limitation that would be >> > appropriate. >> >> So, in the case of MULTITCE, that's not quite right. PR KVM can >> emulate a PAPR system on a BookE machine, and there's no reason not to >> allow TCE acceleration as well. > > That might (or might not; consider things like Altivec versus SPE opcode > conflict, whether unimplemented SPRs trap, behavior of unprivileged > SPRs/instructions, etc) be true in theory, but it's not currently a > supported configuration. BookE KVM does not support emulating a different > CPU than the host. In the unlikely case that ever changes to the point of > allowing PAPR guests on a BookE host, then we can revisit how to properly > determine whether the capability is supported, but for now the capability > will never be valid in the CONFIG_BOOKE case (though I'd rather see it > depend on an appropriate book3s symbol than depend on !BOOKE). > > Or we could just leave it as is, and let it indicate whether the host > kernel supports the feature in general, with the user needing to understand > when it's applicable... I'm a bit confused by the documentation, however > -- the MULTITCE capability was documented in the "capabilities that can be > enabled" section, but I don't see where it can be enabled. True, it cannot be enabled (but it could be enabled a long time ago), it is either supported or not, I'll fix the documentation. Thanks! -- Alexey -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
