KVM: PPC: Book3S HV: Run HPT guests on POWER9 radix hosts

This patch removes the restriction that a radix host can only run
radix guests, allowing us to run HPT (hashed page table) guests as
well.  This is useful because it provides a way to run old guest
kernels that know about POWER8 but not POWER9.

Unfortunately, POWER9 currently has a restriction that all threads
in a given code must either all be in HPT mode, or all in radix mode.
This means that when entering a HPT guest, we have to obtain control
of all 4 threads in the core and get them to switch their LPIDR and
LPCR registers, even if they are not going to run a guest.  On guest
exit we also have to get all threads to switch LPIDR and LPCR back
to host values.

To make this feasible, we require that KVM not be in the "independent
threads" mode, and that the CPU cores be in single-threaded mode from
the host kernel's perspective (only thread 0 online; threads 1, 2 and
3 offline).  That allows us to use the same code as on POWER8 for
obtaining control of the secondary threads.

To manage the LPCR/LPIDR changes required, we extend the kvm_split_info
struct to contain the information needed by the secondary threads.
All threads perform a barrier synchronization (where all threads wait
for every other thread to reach the synchronization point) on guest
entry, both before and after loading LPCR and LPIDR.  On guest exit,
they all once again perform a barrier synchronization both before
and after loading host values into LPCR and LPIDR.

Finally, it is also currently necessary to flush the entire TLB every
time we enter a HPT guest on a radix host.  We do this on thread 0
with a loop of tlbiel instructions.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 12 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s_asm.h b/arch/powerpc/include/asm/kvm_book3s_asm.h
index 7cea76f11c26..ab386af2904f 100644
--- a/arch/powerpc/include/asm/kvm_book3s_asm.h
+++ b/arch/powerpc/include/asm/kvm_book3s_asm.h
@@ -82,6 +82,16 @@ struct kvm_split_mode {
 	u8		do_nap;
 	u8		napped[MAX_SMT_THREADS];
 	struct kvmppc_vcore *vc[MAX_SUBCORES];
+	/* Bits for changing lpcr on P9 */
+	unsigned long	lpcr_req;
+	unsigned long	lpidr_req;
+	unsigned long	host_lpcr;
+	u32		do_set;
+	u32		do_restore;
+	union {
+		u32	allphases;
+		u8	phase[4];
+	} lpcr_sync;
 };
 
 /*
@@ -107,7 +117,8 @@ struct kvmppc_host_state {
 	u8 hwthread_req;
 	u8 hwthread_state;
 	u8 host_ipi;
-	u8 ptid;
+	u8 ptid;		/* thread number within subcore when split */
+	u8 tid;			/* thread number within whole core */
 	struct kvm_vcpu *kvm_vcpu;
 	struct kvmppc_vcore *kvm_vcore;
 	void __iomem *xics_phys;