On Tue, May 09, 2017 at 06:41:23AM +0200, Thomas Huth wrote: > On 09.05.2017 05:45, David Gibson wrote: > > POWER9 DD1 silicon has some bugs which mean it a) isn't really compliant > > with the ISA v3.00 and b) require a number of special workarounds in the > > kernel. > > > > At the moment, qemu isn't aware of DD1. For TCG we don't really want it to > > be (why bother emulating buggy silicon). But with KVM, the guest does need > > to be aware of DD1 so it can apply the necessary workarounds. > > > > Meanwhile, the feature negotiation between qemu and the guest strongly > > favours architected compatibility modes to "raw" CPU modes. In combination > > with the above, this means the guest sees architected POWER9 mode, and > > doesn't apply the DD1 workarounds. Well, unless it has yet another > > workaround to partially ignore what qemu tells it. > > > > This patch addresses this by disabling support for compatibility modes when > > using KVM on a POWER9 DD1 host. > > I first though: Hey, it should be fixed in the guest kernel instead, but > thinking about this twice, I think you're right. If the CPU is not fully > compatible to the ISA, we really should not announce it as "architected > / compatible POWER9" in QEMU. > So basically ACK to your patch, I've just got a cosmetic request below... > > > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au> > > --- > > target/ppc/kvm.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c > > index 8574c36..591b5b5 100644 > > --- a/target/ppc/kvm.c > > +++ b/target/ppc/kvm.c > > @@ -2380,6 +2380,17 @@ static void kvmppc_host_cpu_class_init(ObjectClass > > *oc, void *data) > > > > #if defined(TARGET_PPC64) > > pcc->radix_page_info = kvm_get_radix_page_info(); > > + > > + if ((pcc->pvr & 0xffffff00) == 0x004e0100) { > > Could you please add a proper #define for that magic DD1.0 value to > cpu-models.h, please?
Good point, done. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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