[Qemu-devel] [PATCHv2 2/3] target-ppc: Add helpers for updating a CPU's SDR1 and external HPT

[David Gibson <david@gibson.dropbear.id.au>]

When a Power cpu with 64-bit hash MMU has it's hash page table (HPT)
pointer updated by a write to the SDR1 register we need to update some
derived variables.  Likewise, when the cpu is configured for an external
HPT (one not in the guest memory space) some derived variables need to be
updated.

Currently the logic for this is (partially) duplicated in ppc_store_sdr1()
and in spapr_cpu_reset().  In future we're going to need it in some other
places, so make some common helpers for this update.

In addition the new ppc_hash64_set_external_hpt() helper also updates
SDR1 in KVM - it's not updated by the normal runtime KVM <-> qemu CPU
synchronization.  In a sense this belongs logically in the
ppc_hash64_set_sdr1() helper, but that is called from
kvm_arch_get_registers() so can't itself call cpu_synchronize_state()
without infinite recursion.  In practice this doesn't matter because
the only other caller is TCG specific.

Currently there aren't situations where updating SDR1 at runtime in KVM
matters, but there are going to be in future.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c          | 13 ++-----------
 target-ppc/kvm.c        |  2 +-
 target-ppc/kvm_ppc.h    |  6 ++++++
 target-ppc/mmu-hash64.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 target-ppc/mmu-hash64.h |  6 ++++++
 target-ppc/mmu_helper.c | 13 ++++++-------
 6 files changed, 64 insertions(+), 19 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 64c4acc..72a018b 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1196,17 +1196,8 @@ static void spapr_cpu_reset(void *opaque)
 
     env->spr[SPR_HIOR] = 0;
 
-    env->external_htab = (uint8_t *)spapr->htab;
-    env->htab_base = -1;
-    /*
-     * htab_mask is the mask used to normalize hash value to PTEG index.
-     * htab_shift is log2 of hash table size.
-     * We have 8 hpte per group, and each hpte is 16 bytes.
-     * ie have 128 bytes per hpte entry.
-     */
-    env->htab_mask = (1ULL << (spapr->htab_shift - 7)) - 1;
-    env->spr[SPR_SDR1] = (target_ulong)(uintptr_t)spapr->htab |
-        (spapr->htab_shift - 18);
+    ppc_hash64_set_external_hpt(cpu, spapr->htab, spapr->htab_shift,
+                                &error_fatal);
 }
 
 static void spapr_create_nvram(sPAPRMachineState *spapr)
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 8a762e8..380dff6 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -867,7 +867,7 @@ static int kvm_put_vpa(CPUState *cs)
 }
 #endif /* TARGET_PPC64 */
 
-static int kvmppc_put_books_sregs(PowerPCCPU *cpu)
+int kvmppc_put_books_sregs(PowerPCCPU *cpu)
 {
     CPUPPCState *env = &cpu->env;
     struct kvm_sregs sregs;
diff --git a/target-ppc/kvm_ppc.h b/target-ppc/kvm_ppc.h
index fd64c44..fc79312 100644
--- a/target-ppc/kvm_ppc.h
+++ b/target-ppc/kvm_ppc.h
@@ -55,6 +55,7 @@ void kvmppc_hash64_write_pte(CPUPPCState *env, target_ulong pte_index,
                              target_ulong pte0, target_ulong pte1);
 bool kvmppc_has_cap_fixup_hcalls(void);
 int kvmppc_enable_hwrng(void);
+int kvmppc_put_books_sregs(PowerPCCPU *cpu);
 
 #else
 
@@ -246,6 +247,11 @@ static inline int kvmppc_enable_hwrng(void)
 {
     return -1;
 }
+
+static inline int kvmppc_put_books_sregs(PowerPCCPU *cpu)
+{
+    abort();
+}
 #endif
 
 #ifndef CONFIG_KVM
diff --git a/target-ppc/mmu-hash64.c b/target-ppc/mmu-hash64.c
index 9c58fbf..7b5200b 100644
--- a/target-ppc/mmu-hash64.c
+++ b/target-ppc/mmu-hash64.c
@@ -258,6 +258,49 @@ target_ulong helper_load_slb_vsid(CPUPPCState *env, target_ulong rb)
 /*
  * 64-bit hash table MMU handling
  */
+void ppc_hash64_set_sdr1(PowerPCCPU *cpu, target_ulong value,
+                         Error **errp)
+{
+    CPUPPCState *env = &cpu->env;
+    target_ulong htabsize = value & SDR_64_HTABSIZE;
+
+    env->spr[SPR_SDR1] = value;
+    if (htabsize > 28) {
+        error_setg(errp,
+                   "Invalid HTABSIZE 0x" TARGET_FMT_lx" stored in SDR1",
+                   htabsize);
+        htabsize = 28;
+    }
+    env->htab_mask = (1ULL << (htabsize + 18 - 7)) - 1;
+    env->htab_base = value & SDR_64_HTABORG;
+}
+
+void ppc_hash64_set_external_hpt(PowerPCCPU *cpu, void *hpt, int shift,
+                                 Error **errp)
+{
+    CPUPPCState *env = &cpu->env;
+    Error *local_err = NULL;
+
+    cpu_synchronize_state(CPU(cpu));
+
+    env->external_htab = hpt;
+    ppc_hash64_set_sdr1(cpu, (target_ulong)(uintptr_t)hpt | (shift - 18),
+                        &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    /* Not strictly necessary, but makes it clearer that an external
+     * htab is in use when debugging */
+    env->htab_base = -1;
+
+    if (kvm_enabled()) {
+        if (kvmppc_put_books_sregs(cpu) < 0) {
+            error_setg(errp, "Unable to update SDR1 in KVM");
+        }
+    }
+}
 
 static int ppc_hash64_pte_prot(PowerPCCPU *cpu,
                                ppc_slb_t *slb, ppc_hash_pte64_t pte)
diff --git a/target-ppc/mmu-hash64.h b/target-ppc/mmu-hash64.h
index e7d9925..138cd7e 100644
--- a/target-ppc/mmu-hash64.h
+++ b/target-ppc/mmu-hash64.h
@@ -92,6 +92,12 @@ unsigned ppc_hash64_hpte_page_shift_noslb(PowerPCCPU *cpu,
 
 
 extern bool kvmppc_kern_htab;
+
+void ppc_hash64_set_sdr1(PowerPCCPU *cpu, target_ulong value,
+                         Error **errp);
+void ppc_hash64_set_external_hpt(PowerPCCPU *cpu, void *hpt, int shift,
+                                 Error **errp);
+
 uint64_t ppc_hash64_start_access(PowerPCCPU *cpu, target_ulong pte_index);
 void ppc_hash64_stop_access(uint64_t token);
 
diff --git a/target-ppc/mmu_helper.c b/target-ppc/mmu_helper.c
index e5ec8d6..fcb2cc5 100644
--- a/target-ppc/mmu_helper.c
+++ b/target-ppc/mmu_helper.c
@@ -2005,15 +2005,14 @@ void ppc_store_sdr1(CPUPPCState *env, target_ulong value)
     env->spr[SPR_SDR1] = value;
 #if defined(TARGET_PPC64)
     if (env->mmu_model & POWERPC_MMU_64) {
-        target_ulong htabsize = value & SDR_64_HTABSIZE;
+        PowerPCCPU *cpu = ppc_env_get_cpu(env);
+        Error *local_err = NULL;
 
-        if (htabsize > 28) {
-            fprintf(stderr, "Invalid HTABSIZE 0x" TARGET_FMT_lx
-                    " stored in SDR1\n", htabsize);
-            htabsize = 28;
+        ppc_hash64_set_sdr1(cpu, value, &local_err);
+        if (local_err) {
+            error_report_err(local_err);
+            error_free(local_err);
         }
-        env->htab_mask = (1ULL << (htabsize + 18 - 7)) - 1;
-        env->htab_base = value & SDR_64_HTABORG;
     } else
 #endif /* defined(TARGET_PPC64) */
     {
-- 
2.5.0