[Qemu-devel] [PATCH v3 8/9] spapr: Implement processor compatibility in ibm, client-architecture-support

[Alexey Kardashevskiy <aik@ozlabs.ru>]

Modern Linux kernels support last POWERPC CPUs so when a kernel boots,
in most cases it can find a matching cpu_spec in the kernel's cpu_specs
list. However if the kernel is quite old, it may be missing a definition
of the actual CPU. To provide an ability for old kernels to work on modern
hardware, a Processor Compatibility Mode has been introduced
by the PowerISA specification.

>From the hardware prospective, it is supported by the Processor
Compatibility Register (PCR) which is defined in PowerISA. The register
enables one of the compatibility modes (2.05/2.06/2.07).
Since PCR is a hypervisor privileged register and cannot be
directly accessed from the guest, the mode selection is done via
ibm,client-architecture-support (CAS) RTAS call using which the guest
specifies what "raw" and "architected" CPU versions it supports.
QEMU works out the best match, changes a "cpu-version" property of
every CPU and notifies the guest about the change by setting these
properties in the buffer passed as a response on a custom H_CAS hypercall.

This implements ibm,client-architecture-support parameters parsing
(now only for PVRs) and cooks the device tree diff with new values for
"cpu-version", "ibm,ppc-interrupt-server#s" and
"ibm,ppc-interrupt-server#s" properties.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v3:
* moved ppc_set_compat invocation in h_cas() to run_on_cpu()
* loop no more than 512 times over PVR list (safety net)
---
 hw/ppc/spapr.c       |   4 +-
 hw/ppc/spapr_hcall.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++
 trace-events         |   4 ++
 3 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 14c72d9..020426a 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -34,6 +34,7 @@
 #include "sysemu/kvm.h"
 #include "kvm_ppc.h"
 #include "mmu-hash64.h"
+#include "qom/cpu.h"
 
 #include "hw/boards.h"
 #include "hw/ppc/ppc.h"
@@ -601,7 +602,8 @@ int spapr_h_cas_compose_response(target_ulong addr, target_ulong size)
     _FDT((fdt_open_into(fdt_skel, fdt, size)));
     g_free(fdt_skel);
 
-    /* Place to make changes to the tree */
+    /* Fix skeleton up */
+    _FDT((spapr_fixup_cpu_dt(fdt, spapr)));
 
     /* Pack resulting tree */
     _FDT((fdt_pack(fdt)));
diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index 2f6aa5c..a7460ab 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -3,6 +3,9 @@
 #include "helper_regs.h"
 #include "hw/ppc/spapr.h"
 #include "mmu-hash64.h"
+#include "cpu-models.h"
+#include "trace.h"
+#include "kvm_ppc.h"
 
 struct SPRSyncState {
     CPUState *cs;
@@ -752,12 +755,115 @@ out:
     return ret;
 }
 
+typedef struct {
+    PowerPCCPU *cpu;
+    uint32_t cpu_version;
+    int ret;
+} SetCompatState;
+
+static void do_set_compat(void *arg)
+{
+    SetCompatState *s = arg;
+
+    cpu_synchronize_state(CPU(s->cpu));
+    s->ret = ppc_set_compat(s->cpu, s->cpu_version);
+}
+
+#define get_compat_level(cpuver) ( \
+    ((cpuver) == CPU_POWERPC_LOGICAL_2_05) ? 2050 : \
+    ((cpuver) == CPU_POWERPC_LOGICAL_2_06) ? 2060 : \
+    ((cpuver) == CPU_POWERPC_LOGICAL_2_06_PLUS) ? 2061 : \
+    ((cpuver) == CPU_POWERPC_LOGICAL_2_07) ? 2070 : 0)
+
 static target_ulong h_client_architecture_support(PowerPCCPU *cpu_,
                                                   sPAPREnvironment *spapr,
                                                   target_ulong opcode,
                                                   target_ulong *args)
 {
     target_ulong list = args[0];
+    PowerPCCPUClass *pcc_ = POWERPC_CPU_GET_CLASS(cpu_);
+    CPUState *cs;
+    bool cpu_match = false;
+    unsigned old_cpu_version = cpu_->cpu_version;
+    unsigned compat_lvl = 0, cpu_version = 0;
+    unsigned max_lvl = get_compat_level(cpu_->max_compat);
+    int counter;
+
+    /* Parse PVR list */
+    for (counter = 0; counter < 512; ++counter) {
+        uint32_t pvr, pvr_mask;
+
+        pvr_mask = rtas_ld(list, 0);
+        list += 4;
+        pvr = rtas_ld(list, 0);
+        list += 4;
+
+        trace_spapr_cas_pvr_try(pvr);
+        if (!max_lvl &&
+            ((cpu_->env.spr[SPR_PVR] & pvr_mask) == (pvr & pvr_mask))) {
+            cpu_match = true;
+            cpu_version = 0;
+        } else if (pvr == cpu_->cpu_version) {
+            cpu_match = true;
+            cpu_version = cpu_->cpu_version;
+        } else if (!cpu_match) {
+            /* If it is a logical PVR, try to determine the highest level */
+            unsigned lvl = get_compat_level(pvr);
+            if (lvl) {
+                bool is205 = (pcc_->pcr_mask & PCR_COMPAT_2_05) &&
+                     (lvl == get_compat_level(CPU_POWERPC_LOGICAL_2_05));
+                bool is206 = (pcc_->pcr_mask & PCR_COMPAT_2_06) &&
+                    ((lvl == get_compat_level(CPU_POWERPC_LOGICAL_2_06)) ||
+                    (lvl == get_compat_level(CPU_POWERPC_LOGICAL_2_06_PLUS)));
+
+                if (is205 || is206) {
+                    if (!max_lvl) {
+                        /* User did not set the level, choose the highest */
+                        if (compat_lvl <= lvl) {
+                            compat_lvl = lvl;
+                            cpu_version = pvr;
+                        }
+                    } else if (max_lvl >= lvl) {
+                        /* User chose the level, don't set higher than this */
+                        compat_lvl = lvl;
+                        cpu_version = pvr;
+                    }
+                }
+            }
+        }
+        /* Terminator record */
+        if (~pvr_mask & pvr) {
+            break;
+        }
+    }
+
+    /* For the future use: here @list points to the first capability */
+
+    /* Parsing finished */
+    trace_spapr_cas_pvr(cpu_->cpu_version, cpu_match,
+                        cpu_version, pcc_->pcr_mask);
+
+    /* Update CPUs */
+    if (old_cpu_version != cpu_version) {
+        CPU_FOREACH(cs) {
+            SetCompatState s = {
+                .cpu = POWERPC_CPU(cs),
+                .cpu_version = cpu_version,
+                .ret = 0
+            };
+
+            run_on_cpu(cs, do_set_compat, &s);
+
+            if (s.ret < 0) {
+                fprintf(stderr, "Unable to set compatibility mode\n");
+                return H_HARDWARE;
+            }
+        }
+    }
+
+    if (!cpu_version) {
+        return H_SUCCESS;
+    }
 
     if (!list) {
         return H_SUCCESS;
diff --git a/trace-events b/trace-events
index 98d8e6a..09f4b57 100644
--- a/trace-events
+++ b/trace-events
@@ -1187,6 +1187,10 @@ xics_ics_eoi(int nr) "ics_eoi: irq %#x"
 spapr_cas_failed(unsigned long n) "DT diff buffer is too small: %ld bytes"
 spapr_cas_continue(unsigned long n) "Copy changes to the guest: %ld bytes"
 
+# hw/ppc/spapr_hcall.c
+spapr_cas_pvr_try(uint32_t pvr) "%x"
+spapr_cas_pvr(uint32_t cur_pvr, bool cpu_match, uint32_t new_pvr, uint64_t pcr) "current=%x, cpu_match=%u, new=%x, compat flags=%"PRIx64
+
 # hw/ppc/spapr_iommu.c
 spapr_iommu_put(uint64_t liobn, uint64_t ioba, uint64_t tce, uint64_t ret) "liobn=%"PRIx64" ioba=0x%"PRIx64" tce=0x%"PRIx64" ret=%"PRId64
 spapr_iommu_get(uint64_t liobn, uint64_t ioba, uint64_t ret, uint64_t tce) "liobn=%"PRIx64" ioba=0x%"PRIx64" ret=%"PRId64" tce=0x%"PRIx64
-- 
1.9.rc0