Re: [PATCH 1/2] powerpc/64s: move machine check SLB flushing to mm/slb.c

On Wed, 8 Aug 2018 22:22:52 +0200
Michal Such=C3=A1nek [off-list ref] wrote:

On Fri,  3 Aug 2018 14:13:49 +1000
Nicholas Piggin [off-list ref] wrote:
=20

quoted

The machine check code that flushes and restores bolted segments in
real mode belongs in mm/slb.c. This will be used by pseries machine
check and idle code.
=20
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/include/asm/book3s/64/mmu-hash.h |  3 ++
 arch/powerpc/kernel/mce_power.c               | 21 ++--------
 arch/powerpc/mm/slb.c                         | 38
+++++++++++++++++++ 3 files changed, 44 insertions(+), 18 deletions(-)
=20

diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h

b/arch/powerpc/include/asm/book3s/64/mmu-hash.h index
2f74bdc805e0..d4e398185b3a 100644 ---
a/arch/powerpc/include/asm/book3s/64/mmu-hash.h +++
b/arch/powerpc/include/asm/book3s/64/mmu-hash.h @@ -497,6 +497,9 @@
extern void hpte_init_native(void);=20
 extern void slb_initialize(void);
 extern void slb_flush_and_rebolt(void);
+extern void slb_flush_all_realmode(void);
+extern void __slb_restore_bolted_realmode(void);
+extern void slb_restore_bolted_realmode(void);
=20
 extern void slb_vmalloc_update(void);
 extern void slb_set_size(u16 size);

diff --git a/arch/powerpc/kernel/mce_power.c

b/arch/powerpc/kernel/mce_power.c index d6756af6ec78..50f7b9817246
100644 --- a/arch/powerpc/kernel/mce_power.c

+++ b/arch/powerpc/kernel/mce_power.c

@@ -62,11 +62,8 @@ static unsigned long addr_to_pfn(struct pt_regs

*regs, unsigned long addr) #ifdef CONFIG_PPC_BOOK3S_64
 static void flush_and_reload_slb(void)
 {
-	struct slb_shadow *slb;
-	unsigned long i, n;
-
 	/* Invalidate all SLBs */
-	asm volatile("slbmte %0,%0; slbia" : : "r" (0));
+	slb_flush_all_realmode();
=20
 #ifdef CONFIG_KVM_BOOK3S_HANDLER
 	/*

@@ -76,22 +73,10 @@ static void flush_and_reload_slb(void)
 	if (get_paca()->kvm_hstate.in_guest)
 		return;
 #endif
-
-	/* For host kernel, reload the SLBs from shadow SLB buffer.

*/
-	slb =3D get_slb_shadow();
-	if (!slb)
+	if (early_radix_enabled())
 		return; =20

=20
And we lose the check that the shadow slb exists. Is !slb equivalent to
early_radix_enabled()=20

Yeah pretty close to.

=20

quoted

=20
-	n =3D min_t(u32, be32_to_cpu(slb->persistent), SLB_MIN_SIZE);
-
-	/* Load up the SLB entries from shadow SLB */
-	for (i =3D 0; i < n; i++) {
-		unsigned long rb =3D
be64_to_cpu(slb->save_area[i].esid);
-		unsigned long rs =3D
be64_to_cpu(slb->save_area[i].vsid); -
-		rb =3D (rb & ~0xFFFul) | i;
-		asm volatile("slbmte %0,%1" : : "r" (rs), "r" (rb));
-	}
+	slb_restore_bolted_realmode();
 }
 #endif
=20

diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index cb796724a6fc..136db8652577 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c

@@ -90,6 +90,44 @@ static inline void create_shadowed_slbe(unsigned

long ea, int ssize, : "memory" );
 }
=20
+/*
+ * Insert bolted entries into SLB (which may not be empty).
+ */
+void __slb_restore_bolted_realmode(void)
+{
+	struct slb_shadow *p =3D get_slb_shadow();
+	enum slb_index index; =20

=20
or can we get here at some point when shadow slb is not populated?

We shouldn't because we won't turn the MMU on so we shouldn't get SLB
MCEs... But I don't think that's guaranteed anywhere, so yeah wouldn't
hurt to add that check back in.

I'll send out another revision.

Thanks,
Nick