powerpc/64: Enable use of radix MMU under hypervisor on POWER9

To use radix as a guest, we first need to tell the hypervisor via
the ibm,client-architecture call first that we support POWER9 and
architecture v3.00, and that we can do either radix or hash and
that we would like to choose later using an hcall (the
H_REGISTER_PROC_TBL hcall).

Then we need to check whether the hypervisor agreed to us using
radix.  We need to do this very early on in the kernel boot process
before any of the MMU initialization is done.  If the hypervisor
doesn't agree, we can't use radix and therefore clear the radix
MMU feature bit.

Later, when we have set up our process table, which points to the
radix tree for each process, we need to install that using the
H_REGISTER_PROC_TBL hcall.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index 4d9481ec2468..10c9a545a646 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -347,10 +347,9 @@ static int __init parse_disable_radix(char *p)
 early_param("disable_radix", parse_disable_radix);
 
 /*
- * If we're running under a hypervisor, we currently can't do radix
- * since we don't have the code to do the H_REGISTER_PROC_TBL hcall.
- * We tell that we're running under a hypervisor by looking for the
- * /chosen/ibm,architecture-vec-5 property.
+ * If we're running under a hypervisor, we need to check the contents of
+ * /chosen/ibm,architecture-vec-5 to see if the hypervisor is willing to do
+ * radix.  If not, we clear the radix feature bit so we fall back to hash.
  */
 static void early_check_vec5(void)
 {
@@ -365,7 +364,10 @@ static void early_check_vec5(void)
 	vec5 = of_get_flat_dt_prop(chosen, "ibm,architecture-vec-5", &size);
 	if (!vec5)
 		return;
-	cur_cpu_spec->mmu_features &= ~MMU_FTR_TYPE_RADIX;
+	if (size <= OV5_INDX(OV5_MMU_RADIX_300) ||
+	    !(vec5[OV5_INDX(OV5_MMU_RADIX_300)] & OV5_FEAT(OV5_MMU_RADIX_300)))
+		/* Hypervisor doesn't support radix */
+		cur_cpu_spec->mmu_features &= ~MMU_FTR_TYPE_RADIX;
 }
 
 void __init mmu_early_init_devtree(void)