powerpc/powernv/kvm: Use darn for H_RANDOM on Power9

The existing logic in KVM to support guests calling H_RANDOM only works
on Power8, because it looks for an RNG in the device tree, but on Power9
we just use darn.

In addition the existing code needs to work in real mode, so we have the
special cased powernv_get_random_real_mode() to deal with that.

Instead just have KVM call ppc_md.get_random_seed(), and do the real
mode check inside of there, that way we use whatever RNG is available,
including darn on Power9.

Fixes: e928e9cb3601 ("KVM: PPC: Book3S HV: Add fast real-mode H_RANDOM implementation.")
Cc: stable@vger.kernel.org # v4.1+
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
[mpe: Rebase on previous commit, update change log appropriately]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220727143219.2684192-2-mpe@ellerman.id.au

1 files changed, 8 insertions, 28 deletions

diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
index 2287c9cd0cd5..d19305292e1e 100644
--- a/arch/powerpc/platforms/powernv/rng.c
+++ b/arch/powerpc/platforms/powernv/rng.c
@@ -29,15 +29,6 @@ struct powernv_rng {
 
 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
 
-int powernv_hwrng_present(void)
-{
-	struct powernv_rng *rng;
-
-	rng = get_cpu_var(powernv_rng);
-	put_cpu_var(rng);
-	return rng != NULL;
-}
-
 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
 {
 	unsigned long parity;
@@ -58,19 +49,6 @@ static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
 	return val;
 }
 
-int powernv_get_random_real_mode(unsigned long *v)
-{
-	struct powernv_rng *rng;
-
-	rng = raw_cpu_read(powernv_rng);
-	if (!rng)
-		return 0;
-
-	*v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
-
-	return 1;
-}
-
 static int powernv_get_random_darn(unsigned long *v)
 {
 	unsigned long val;
@@ -107,12 +85,14 @@ int powernv_get_random_long(unsigned long *v)
 {
 	struct powernv_rng *rng;
 
-	rng = get_cpu_var(powernv_rng);
-
-	*v = rng_whiten(rng, in_be64(rng->regs));
-
-	put_cpu_var(rng);
-
+	if (mfmsr() & MSR_DR) {
+		rng = get_cpu_var(powernv_rng);
+		*v = rng_whiten(rng, in_be64(rng->regs));
+		put_cpu_var(rng);
+	} else {
+		rng = raw_cpu_read(powernv_rng);
+		*v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
+	}
 	return 1;
 }
 EXPORT_SYMBOL_GPL(powernv_get_random_long);