target/ppc: Implement large decrementer support for KVM

Implement support to allow KVM guests to take advantage of the large
decrementer introduced on POWER9 cpus.

To determine if the host can support the requested large decrementer
size, we check it matches that specified in the ibm,dec-bits device-tree
property. We also need to enable it in KVM by setting the LPCR_LD bit in
the LPCR. Note that to do this we need to try and set the bit, then read
it back to check the host allowed us to set it, if so we can use it but
if we were unable to set it the host cannot support it and we must not
use the large decrementer.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20190301024317.22137-3-sjitindarsingh@gmail.com>
[dwg: Small style fixes]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 12 insertions, 0 deletions

diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h
index bdfaa4e70a..a79835bd14 100644
--- a/target/ppc/kvm_ppc.h
+++ b/target/ppc/kvm_ppc.h
@@ -64,6 +64,8 @@ int kvmppc_get_cap_safe_bounds_check(void);
 int kvmppc_get_cap_safe_indirect_branch(void);
 bool kvmppc_has_cap_nested_kvm_hv(void);
 int kvmppc_set_cap_nested_kvm_hv(int enable);
+int kvmppc_get_cap_large_decr(void);
+int kvmppc_enable_cap_large_decr(PowerPCCPU *cpu, int enable);
 int kvmppc_enable_hwrng(void);
 int kvmppc_put_books_sregs(PowerPCCPU *cpu);
 PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void);
@@ -332,6 +334,16 @@ static inline int kvmppc_set_cap_nested_kvm_hv(int enable)
     return -1;
 }
 
+static inline int kvmppc_get_cap_large_decr(void)
+{
+    return 0;
+}
+
+static inline int kvmppc_enable_cap_large_decr(PowerPCCPU *cpu, int enable)
+{
+    return -1;
+}
+
 static inline int kvmppc_enable_hwrng(void)
 {
     return -1;