[PATCH] target/ppc: Generate storage interrupts for radix RC changes

[Shawn Anastasio]

Change radix64_set_rc to always generate a storage interrupt when the
R/C bits are not set appropriately instead of setting the bits itself.
According to the ISA both behaviors are valid, but in practice this
change more closely matches behavior observed on the POWER9 CPU.

>From the POWER9 Processor User's Manual, Section 4.10.13.1: "When
performing Radix translation, the POWER9 hardware triggers the
appropriate interrupt ... for the mode and type of access whenever
Reference (R) and Change (C) bits require setting in either the guest or
host page-table entry (PTE)."

Signed-off-by: Shawn Anastasio <sanastasio@raptorengineering.com>
---
 target/ppc/mmu-radix64.c | 57 ++++++++++++++++++++++++++++------------
 1 file changed, 40 insertions(+), 17 deletions(-)

diff --git a/target/ppc/mmu-radix64.c b/target/ppc/mmu-radix64.c
index 920084bd8f..06e1cced31 100644
--- a/target/ppc/mmu-radix64.c
+++ b/target/ppc/mmu-radix64.c
@@ -219,27 +219,48 @@ static bool ppc_radix64_check_prot(PowerPCCPU *cpu, 
MMUAccessType access_type,
     return false;
 }
 
-static void ppc_radix64_set_rc(PowerPCCPU *cpu, MMUAccessType access_type,
-                               uint64_t pte, hwaddr pte_addr, int *prot)
+static int ppc_radix64_check_rc(PowerPCCPU *cpu, MMUAccessType access_type,
+                               uint64_t pte, vaddr eaddr, bool 
partition_scoped,
+                               hwaddr g_raddr)
 {
-    CPUState *cs = CPU(cpu);
-    uint64_t npte;
+    uint64_t lpid = 0;
+    uint64_t pid = 0;
 
-    npte = pte | R_PTE_R; /* Always set reference bit */
+    switch (access_type) {
+    case MMU_DATA_STORE:
+        if (!(pte & R_PTE_C)) {
+            break;
+        }
+        /* fall through */
+    case MMU_INST_FETCH:
+    case MMU_DATA_LOAD:
+        if (!(pte & R_PTE_R)) {
+            break;
+        }
 
-    if (access_type == MMU_DATA_STORE) { /* Store/Write */
-        npte |= R_PTE_C; /* Set change bit */
-    } else {
-        /*
-         * Treat the page as read-only for now, so that a later write
-         * will pass through this function again to set the C bit.
-         */
-        *prot &= ~PAGE_WRITE;
+        /* R/C bits are already set appropriately for this access */
+        return 0;
     }
 
-    if (pte ^ npte) { /* If pte has changed then write it back */
-        stq_phys(cs->as, pte_addr, npte);
+    /* Obtain effLPID */
+    (void)ppc_radix64_get_fully_qualified_addr(&cpu->env, eaddr, &lpid, &pid);
+
+    /*
+     * Per ISA 3.1 Book III, 7.5.3 and 7.5.5, failure to set R/C during
+     * partition-scoped translation when effLPID = 0 results in normal
+     * (non-Hypervisor) Data and Instruction Storage Interrupts respectively.
+     *
+     * ISA 3.0 is ambiguous about this, but tests on POWER9 hardware seem to
+     * exhibit the same behavior.
+     */
+    if (partition_scoped && lpid > 0) {
+        ppc_radix64_raise_hsi(cpu, access_type, eaddr, g_raddr,
+                              DSISR_ATOMIC_RC);
+    } else {
+        ppc_radix64_raise_si(cpu, access_type, eaddr, DSISR_ATOMIC_RC);
     }
+
+    return 1;
 }
 
 static bool ppc_radix64_is_valid_level(int level, int psize, uint64_t nls)
@@ -418,7 +439,8 @@ static int ppc_radix64_partition_scoped_xlate(PowerPCCPU 
*cpu,
     }
 
     if (guest_visible) {
-        ppc_radix64_set_rc(cpu, access_type, pte, pte_addr, h_prot);
+        return ppc_radix64_check_rc(cpu, access_type, pte, eaddr, true,
+                                    g_raddr);
     }
 
     return 0;
@@ -580,7 +602,8 @@ static int ppc_radix64_process_scoped_xlate(PowerPCCPU *cpu,
     }
 
     if (guest_visible) {
-        ppc_radix64_set_rc(cpu, access_type, pte, pte_addr, g_prot);
+        return ppc_radix64_check_rc(cpu, access_type, pte, eaddr, false,
+                                    *g_raddr);
     }
 
     return 0;
-- 
2.30.2