[PULL 41/41] KVM: PPC: Book3S PR: Rework SLB switching code

Alexander Graf
2014-05-30T12:42:56Z

On LPAR guest systems Linux enables the shadow SLB to indicate to the
hypervisor a number of SLB entries that always have to be available.

Today we go through this shadow SLB and disable all ESID's valid bits.
However, pHyp doesn't like this approach very much and honors us with
fancy machine checks.

Fortunately the shadow SLB descriptor also has an entry that indicates
the number of valid entries following. During the lifetime of a guest
we can just swap that value to 0 and don't have to worry about the
SLB restoration magic.

While we're touching the code, let's also make it more readable (get
rid of rldicl), allow it to deal with a dynamic number of bolted
SLB entries and only do shadow SLB swizzling on LPAR systems.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
arch/powerpc/kernel/paca.c | 3 ++
arch/powerpc/kvm/book3s_64_slb.S | 83 ++++++++++++++++++----------------------
arch/powerpc/mm/slb.c | 2 +-
3 files changed, 42 insertions(+), 46 deletions(-)

diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index ad302f8..d6e195e 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -98,6 +98,9 @@ static inline void free_lppacas(void) { }
/*
* 3 persistent SLBs are registered here. The buffer will be zero
* initially, hence will all be invaild until we actually write them.
+ *
+ * If you make the number of persistent SLB entries dynamic, please also
+ * update PR KVM to flush and restore them accordingly.
*/
static struct slb_shadow *slb_shadow;

diff --git a/arch/powerpc/kvm/book3s_64_slb.S b/arch/powerpc/kvm/book3s_64_slb.S
index 84c52c6..3589c4e 100644
--- a/arch/powerpc/kvm/book3s_64_slb.S
+++ b/arch/powerpc/kvm/book3s_64_slb.S
@@ -17,29 +17,9 @@
* Authors: Alexander Graf <agraf@suse.de>
*/

-#define SHADOW_SLB_ESID(num) (SLBSHADOW_SAVEAREA + (num * 0x10))
-#define SHADOW_SLB_VSID(num) (SLBSHADOW_SAVEAREA + (num * 0x10) + 0x8)
-#define UNBOLT_SLB_ENTRY(num) \
- li r11, SHADOW_SLB_ESID(num); \
- LDX_BE r9, r12, r11; \
- /* Invalid? Skip. */; \
- rldicl. r0, r9, 37, 63; \
- beq slb_entry_skip_ ## num; \
- xoris r9, r9, SLB_ESID_V@h; \
- STDX_BE r9, r12, r11; \
- slb_entry_skip_ ## num:
-
-#define REBOLT_SLB_ENTRY(num) \
- li r8, SHADOW_SLB_ESID(num); \
- li r7, SHADOW_SLB_VSID(num); \
- LDX_BE r10, r11, r8; \
- cmpdi r10, 0; \
- beq slb_exit_skip_ ## num; \
- oris r10, r10, SLB_ESID_V@h; \
- LDX_BE r9, r11, r7; \
- slbmte r9, r10; \
- STDX_BE r10, r11, r8; \
-slb_exit_skip_ ## num:
+#define SHADOW_SLB_ENTRY_LEN 0x10
+#define OFFSET_ESID(x) (SHADOW_SLB_ENTRY_LEN * x)
+#define OFFSET_VSID(x) ((SHADOW_SLB_ENTRY_LEN * x) + 8)

/******************************************************************************
* *
@@ -63,20 +43,15 @@ slb_exit_skip_ ## num:
* SVCPU[LR] = guest LR
*/

- /* Remove LPAR shadow entries */
+BEGIN_FW_FTR_SECTION

-#if SLB_NUM_BOLTED == 3
+ /* Declare SLB shadow as 0 entries big */

- ld r12, PACA_SLBSHADOWPTR(r13)
+ ld r11, PACA_SLBSHADOWPTR(r13)
+ li r8, 0
+ stb r8, 3(r11)

- /* Remove bolted entries */
- UNBOLT_SLB_ENTRY(0)
- UNBOLT_SLB_ENTRY(1)
- UNBOLT_SLB_ENTRY(2)
-
-#else
-#error unknown number of bolted entries
-#endif
+END_FW_FTR_SECTION_IFSET(FW_FEATURE_LPAR)

/* Flush SLB */

@@ -99,7 +74,7 @@ slb_loop_enter:

ld r10, 0(r11)

- rldicl. r0, r10, 37, 63
+ andis. r9, r10, SLB_ESID_V@h
beq slb_loop_enter_skip

ld r9, 8(r11)
@@ -136,24 +111,42 @@ slb_do_enter:
*
*/

- /* Restore bolted entries from the shadow and fix it along the way */
+ /* Remove all SLB entries that are in use. */

li r0, r0
slbmte r0, r0
slbia
- isync

-#if SLB_NUM_BOLTED == 3
+ /* Restore bolted entries from the shadow */

ld r11, PACA_SLBSHADOWPTR(r13)

- REBOLT_SLB_ENTRY(0)
- REBOLT_SLB_ENTRY(1)
- REBOLT_SLB_ENTRY(2)
-
-#else
-#error unknown number of bolted entries
-#endif
+BEGIN_FW_FTR_SECTION
+
+ /* Declare SLB shadow as SLB_NUM_BOLTED entries big */
+
+ li r8, SLB_NUM_BOLTED
+ stb r8, 3(r11)
+
+END_FW_FTR_SECTION_IFSET(FW_FEATURE_LPAR)
+
+ /* Manually load all entries from shadow SLB */
+
+ li r8, SLBSHADOW_SAVEAREA
+ li r7, SLBSHADOW_SAVEAREA + 8
+
+ .rept SLB_NUM_BOLTED
+ LDX_BE r10, r11, r8
+ cmpdi r10, 0
+ beq 1f
+ LDX_BE r9, r11, r7
+ slbmte r9, r10
+1: addi r7, r7, SHADOW_SLB_ENTRY_LEN
+ addi r8, r8, SHADOW_SLB_ENTRY_LEN
+ .endr
+
+ isync
+ sync

slb_do_exit:

diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index 9d1d33c..964a5f6 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -97,7 +97,7 @@ static inline void create_shadowed_slbe(unsigned long ea, int ssize,
static void __slb_flush_and_rebolt(void)
{
/* If you change this make sure you change SLB_NUM_BOLTED
- * appropriately too. */
+ * and PR KVM appropriately too. */
unsigned long linear_llp, vmalloc_llp, lflags, vflags;
unsigned long ksp_esid_data, ksp_vsid_data;

--
1.8.1.4