target/ppc: Allow workarounds for POWER9 DD1

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.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

diff --git a/target/ppc/cpu-models.h b/target/ppc/cpu-models.h
index d587e69bbcdd129c6891a54c77cfa73d7342c8e0..b563c45b682979670b57d46d5d5b79f51960bd9a 100644 (file)
--- a/target/ppc/cpu-models.h
+++ b/target/ppc/cpu-models.h
@@ -561,6 +561,7 @@ enum {
     CPU_POWERPC_POWER8NVL_BASE     = 0x004C0000,
     CPU_POWERPC_POWER8NVL_v10      = 0x004C0100,
     CPU_POWERPC_POWER9_BASE        = 0x004E0000,
+    CPU_POWERPC_POWER9_DD1         = 0x004E0100,
     CPU_POWERPC_970_v22            = 0x00390202,
     CPU_POWERPC_970FX_v10          = 0x00391100,
     CPU_POWERPC_970FX_v20          = 0x003C0200,

diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index 8574c369e6833299bdccdb8dc1d4cbe9c8e3f7ed..cb2cf2b1079697c0f88e0f81452a921cb39df3d2 100644 (file)
--- 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) == CPU_POWERPC_POWER9_DD1) {
+        /*
+         * POWER9 DD1 has some bugs which make it not really ISA 3.00
+         * compliant.  More importantly, advertising ISA 3.00
+         * architected mode may prevent guests from activating
+         * necessary DD1 workarounds.
+         */
+        pcc->pcr_supported &= ~(PCR_COMPAT_3_00 | PCR_COMPAT_2_07
+                                | PCR_COMPAT_2_06 | PCR_COMPAT_2_05);
+    }
 #endif /* defined(TARGET_PPC64) */
 }