[Qemu-devel] [RFC PATCH 3/4] ppc: Use split I/D mmu modes to avoid flushes on interrupts

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

We rework the way the MMU indices are calculated, providing separate
indices for I and D side based on MSR:IR and MSR:DR respectively,
and thus no longer need to flush the TLB on context changes. This also
adds correct support for HV as a separate address space.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 target-ppc/cpu.h         | 11 +++++++---
 target-ppc/excp_helper.c | 13 ++++--------
 target-ppc/helper_regs.h | 54 ++++++++++++++++++++++++++++++++++++++++++------
 target-ppc/machine.c     |  4 +++-
 target-ppc/translate.c   |  7 ++++---
 5 files changed, 67 insertions(+), 22 deletions(-)

diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index 0a0c47e..04c4885 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -462,6 +462,8 @@ struct ppc_slb_t {
 #define MSR_EP   6  /* Exception prefix on 601                               */
 #define MSR_IR   5  /* Instruction relocate                                  */
 #define MSR_DR   4  /* Data relocate                                         */
+#define MSR_IS   5  /* Instruction address space (BookE)                     */
+#define MSR_DS   4  /* Data address space (BookE)                            */
 #define MSR_PE   3  /* Protection enable on 403                              */
 #define MSR_PX   2  /* Protection exclusive on 403                  x        */
 #define MSR_PMM  2  /* Performance monitor mark on POWER            x        */
@@ -505,6 +507,8 @@ struct ppc_slb_t {
 #define msr_ep   ((env->msr >> MSR_EP)   & 1)
 #define msr_ir   ((env->msr >> MSR_IR)   & 1)
 #define msr_dr   ((env->msr >> MSR_DR)   & 1)
+#define msr_is   ((env->msr >> MSR_IS)   & 1)
+#define msr_ds   ((env->msr >> MSR_DS)   & 1)
 #define msr_pe   ((env->msr >> MSR_PE)   & 1)
 #define msr_px   ((env->msr >> MSR_PX)   & 1)
 #define msr_pmm  ((env->msr >> MSR_PMM)  & 1)
@@ -944,7 +948,7 @@ struct ppc_segment_page_sizes {
 
 /*****************************************************************************/
 /* The whole PowerPC CPU context */
-#define NB_MMU_MODES 3
+#define NB_MMU_MODES    6
 
 #define PPC_CPU_OPCODES_LEN          0x40
 #define PPC_CPU_INDIRECT_OPCODES_LEN 0x20
@@ -1107,7 +1111,8 @@ struct CPUPPCState {
     /* Those resources are used only in QEMU core */
     target_ulong hflags;      /* hflags is a MSR & HFLAGS_MASK         */
     target_ulong hflags_nmsr; /* specific hflags, not coming from MSR */
-    int mmu_idx;         /* precomputed MMU index to speed up mem accesses */
+    int immu_idx;         /* precomputed MMU index to speed up insn access */
+    int dmmu_idx;         /* precomputed MMU index to speed up data accesses */
 
     /* Power management */
     int (*check_pow)(CPUPPCState *env);
@@ -1249,7 +1254,7 @@ int ppc_dcr_write (ppc_dcr_t *dcr_env, int dcrn, uint32_t val);
 #define MMU_USER_IDX 0
 static inline int cpu_mmu_index (CPUPPCState *env, bool ifetch)
 {
-    return env->mmu_idx;
+    return ifetch ? env->immu_idx : env->dmmu_idx;
 }
 
 #include "exec/cpu-all.h"
diff --git a/target-ppc/excp_helper.c b/target-ppc/excp_helper.c
index b803475..e2f82d2 100644
--- a/target-ppc/excp_helper.c
+++ b/target-ppc/excp_helper.c
@@ -623,9 +623,6 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int excp_model, int excp)
 
     if (env->spr[SPR_LPCR] & LPCR_AIL) {
         new_msr |= (1 << MSR_IR) | (1 << MSR_DR);
-    } else if (msr & ((1 << MSR_IR) | (1 << MSR_DR))) {
-        /* If we disactivated any translation, flush TLBs */
-        tlb_flush(cs, 1);
     }
 
 #ifdef TARGET_PPC64
@@ -675,12 +672,10 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int excp_model, int excp)
     cs->exception_index = POWERPC_EXCP_NONE;
     env->error_code = 0;
 
-    if ((env->mmu_model == POWERPC_MMU_BOOKE) ||
-        (env->mmu_model == POWERPC_MMU_BOOKE206)) {
-        /* XXX: The BookE changes address space when switching modes,
-                we should probably implement that as different MMU indexes,
-                but for the moment we do it the slow way and flush all.  */
-        tlb_flush(cs, 1);
+    if (env->mmu_model & POWERPC_MMU_BOOKE) {
+        if ((msr ^ new_msr) & (1u << MSR_GS)) {
+            tlb_flush(cs, 1);
+        }
     }
 }
 
diff --git a/target-ppc/helper_regs.h b/target-ppc/helper_regs.h
index 271fddf..70615f1 100644
--- a/target-ppc/helper_regs.h
+++ b/target-ppc/helper_regs.h
@@ -41,11 +41,50 @@ static inline void hreg_swap_gpr_tgpr(CPUPPCState *env)
 
 static inline void hreg_compute_mem_idx(CPUPPCState *env)
 {
-    /* Precompute MMU index */
-    if (msr_pr == 0 && msr_hv != 0) {
-        env->mmu_idx = 2;
+    /* This is our encoding for server processors:
+     *
+     *   0 = Guest User space virtual mode
+     *   1 = Guest Kenrel space virtual mode
+     *   2 = Guest Kernel space real mode
+     *   3 = HV User space virtual mode
+     *   4 = HV Kenrel space virtual mode
+     *   5 = HV Kernel space real mode
+     *
+     * The combination PR=1 IR&DR=0 is invalid, we will treat
+     * it as IR=DR=1
+     *
+     * For BookE, we need in theory 8 MMU modes, which would
+     * reduce performance, so instead, we ignore msr_hv and
+     * will flush on HV context switches. We *could* improve
+     * things a bit if needed by using 4 and 5 as HV and flush
+     * only when HV mode changes AS but that complicates things
+     * as we would need to remember which is the current AS mode
+     * for HV for I and D and split more would be hell.
+     *
+     *  0 = AS 0 User space
+     *  1 = AS 0 Kernel space
+     *  2 = AS 1 User space
+     *  3 = AS 1 Kernel space
+     */
+    if (env->mmu_model & POWERPC_MMU_BOOKE) {
+        env->immu_idx = env->dmmu_idx = msr_pr ? 0 : 1;
+        env->immu_idx += msr_is ? 2 : 0;
+        env->dmmu_idx += msr_ds ? 2 : 0;
     } else {
-        env->mmu_idx = 1 - msr_pr;
+        /* First calucalte a base value independent of HV */
+        if (msr_pr != 0) {
+            /* User space, ignore IR and DR */
+            env->immu_idx = env->dmmu_idx = 0;
+        } else {
+            /* Kernel, setup a base I/D value */
+            env->immu_idx = msr_ir ? 1 : 2;
+            env->dmmu_idx = msr_dr ? 1 : 2;
+        }
+        /* Then offset it for HV */
+        if (msr_hv) {
+            env->immu_idx += 3;
+            env->dmmu_idx += 3;
+        }
     }
 }
 
@@ -82,11 +121,14 @@ static inline int hreg_store_msr(CPUPPCState *env, target_ulong value,
     }
     if (((value >> MSR_IR) & 1) != msr_ir ||
         ((value >> MSR_DR) & 1) != msr_dr) {
-        /* Flush all tlb when changing translation mode */
-        tlb_flush(cs, 1);
         excp = POWERPC_EXCP_NONE;
         cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
     }
+    if ((env->mmu_model & POWERPC_MMU_BOOKE) &&
+        ((value >> MSR_GS) & 1) != msr_gs) {
+         /* Flush all tlb when changing guest mode */
+         tlb_flush(cs, 1);
+    }
     if (unlikely((env->flags & POWERPC_FLAG_TGPR) &&
                  ((value ^ env->msr) & (1 << MSR_TGPR)))) {
         /* Swap temporary saved registers with GPRs */
diff --git a/target-ppc/machine.c b/target-ppc/machine.c
index f4ac761..b969492 100644
--- a/target-ppc/machine.c
+++ b/target-ppc/machine.c
@@ -90,9 +90,11 @@ static int cpu_load_old(QEMUFile *f, void *opaque, int version_id)
     qemu_get_betls(f, &env->nip);
     qemu_get_betls(f, &env->hflags);
     qemu_get_betls(f, &env->hflags_nmsr);
-    qemu_get_sbe32s(f, &env->mmu_idx);
     qemu_get_sbe32(f); /* Discard unused power_mode */
 
+    /* Ignore saved mmu_idx, recompute */
+    hreg_compute_mem_idx(env);
+
     return 0;
 }
 
diff --git a/target-ppc/translate.c b/target-ppc/translate.c
index 84c5cea..dee0cc8 100644
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -11213,8 +11213,9 @@ void ppc_cpu_dump_state(CPUState *cs, FILE *f, fprintf_function cpu_fprintf,
                 env->nip, env->lr, env->ctr, cpu_read_xer(env),
                 cs->cpu_index);
     cpu_fprintf(f, "MSR " TARGET_FMT_lx " HID0 " TARGET_FMT_lx "  HF "
-                TARGET_FMT_lx " idx %d\n", env->msr, env->spr[SPR_HID0],
-                env->hflags, env->mmu_idx);
+                TARGET_FMT_lx " iidx %d didx %d\n",
+                env->msr, env->spr[SPR_HID0],
+                env->hflags, env->immu_idx, env->dmmu_idx);
 #if !defined(NO_TIMER_DUMP)
     cpu_fprintf(f, "TB %08" PRIu32 " %08" PRIu64
 #if !defined(CONFIG_USER_ONLY)
@@ -11423,7 +11424,7 @@ static inline void gen_intermediate_code_internal(PowerPCCPU *cpu,
     ctx.spr_cb = env->spr_cb;
     ctx.pr = msr_pr;
     ctx.hv = !msr_pr && msr_hv;
-    ctx.mem_idx = env->mmu_idx;
+    ctx.mem_idx = env->dmmu_idx;
     ctx.insns_flags = env->insns_flags;
     ctx.insns_flags2 = env->insns_flags2;
     ctx.access_type = -1;
-- 
2.1.4