[Qemu-devel] [PATCH v4 16/18] spapr_rtas_ddw: Workaround broken LE guests

[Alexey Kardashevskiy <aik@ozlabs.ru>]

Recent kernels do parse results of what DDW RTAS calls return incorrectly
if compiled with LITTLE_ENDIAN=yes.

This adds special handling for such guests.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/ppc/spapr_rtas.c     | 29 +++++++++++++++++++++++++++++
 hw/ppc/spapr_rtas_ddw.c | 40 ++++++++++++++++++++++++++++++++++++++++
 include/hw/ppc/spapr.h  |  2 ++
 3 files changed, 71 insertions(+)

diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index 2ec2a8e..c3dee94 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -293,12 +293,15 @@ static void rtas_ibm_os_term(PowerPCCPU *cpu,
 static struct rtas_call {
     const char *name;
     spapr_rtas_fn fn;
+    spapr_rtas_fn fn_wa; /* workaround helper */
 } rtas_table[RTAS_TOKEN_MAX - RTAS_TOKEN_BASE];
 
 target_ulong spapr_rtas_call(PowerPCCPU *cpu, sPAPREnvironment *spapr,
                              uint32_t token, uint32_t nargs, target_ulong args,
                              uint32_t nret, target_ulong rets)
 {
+    uint32_t tokensw = bswap32(token);
+
     if ((token >= RTAS_TOKEN_BASE) && (token < RTAS_TOKEN_MAX)) {
         struct rtas_call *call = rtas_table + (token - RTAS_TOKEN_BASE);
 
@@ -308,6 +311,16 @@ target_ulong spapr_rtas_call(PowerPCCPU *cpu, sPAPREnvironment *spapr,
         }
     }
 
+    /* Workaround for LE guests */
+    if ((tokensw >= RTAS_TOKEN_BASE) && (tokensw < RTAS_TOKEN_MAX)) {
+        struct rtas_call *call = rtas_table + (tokensw - RTAS_TOKEN_BASE);
+
+        if (call->fn_wa) {
+            call->fn_wa(cpu, spapr, tokensw, nargs, args, nret, rets);
+            return H_SUCCESS;
+        }
+    }
+
     /* HACK: Some Linux early debug code uses RTAS display-character,
      * but assumes the token value is 0xa (which it is on some real
      * machines) without looking it up in the device tree.  This
@@ -340,6 +353,22 @@ void spapr_rtas_register(int token, const char *name, spapr_rtas_fn fn)
     rtas_table[token].fn = fn;
 }
 
+void spapr_rtas_register_wrong_endian(int token, spapr_rtas_fn fn)
+{
+    if (!((token >= RTAS_TOKEN_BASE) && (token < RTAS_TOKEN_MAX))) {
+        fprintf(stderr, "RTAS invalid token 0x%x\n", token);
+        exit(1);
+    }
+
+    token -= RTAS_TOKEN_BASE;
+    if (!rtas_table[token].fn) {
+        fprintf(stderr, "RTAS token %x must be initialized to allow workaround\n",
+                token);
+        exit(1);
+    }
+    rtas_table[token].fn_wa = fn;
+}
+
 int spapr_rtas_device_tree_setup(void *fdt, hwaddr rtas_addr,
                                  hwaddr rtas_size)
 {
diff --git a/hw/ppc/spapr_rtas_ddw.c b/hw/ppc/spapr_rtas_ddw.c
index af70601..56eae9f 100644
--- a/hw/ppc/spapr_rtas_ddw.c
+++ b/hw/ppc/spapr_rtas_ddw.c
@@ -278,6 +278,41 @@ param_error_exit:
     rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
 }
 
+#define SPAPR_RTAS_DDW_SWAP(n) rtas_st(rets, (n), bswap32(rtas_ld(rets, (n))))
+
+static void rtas_ibm_query_pe_dma_window_wrong_endian(PowerPCCPU *cpu,
+                                                      sPAPREnvironment *spapr,
+                                                      uint32_t token,
+                                                      uint32_t nargs,
+                                                      target_ulong args,
+                                                      uint32_t nret,
+                                                      target_ulong rets)
+{
+    rtas_ibm_query_pe_dma_window(cpu, spapr, token, nargs, args, nret, rets);
+
+    SPAPR_RTAS_DDW_SWAP(0);
+    SPAPR_RTAS_DDW_SWAP(1);
+    SPAPR_RTAS_DDW_SWAP(2);
+    SPAPR_RTAS_DDW_SWAP(3);
+    SPAPR_RTAS_DDW_SWAP(4);
+}
+
+static void rtas_ibm_create_pe_dma_window_wrong_endian(PowerPCCPU *cpu,
+                                                       sPAPREnvironment *spapr,
+                                                       uint32_t token,
+                                                       uint32_t nargs,
+                                                       target_ulong args,
+                                                       uint32_t nret,
+                                                       target_ulong rets)
+{
+    rtas_ibm_create_pe_dma_window(cpu, spapr, token, nargs, args, nret, rets);
+
+    SPAPR_RTAS_DDW_SWAP(0);
+    SPAPR_RTAS_DDW_SWAP(1);
+    SPAPR_RTAS_DDW_SWAP(2);
+    SPAPR_RTAS_DDW_SWAP(3);
+}
+
 static void spapr_rtas_ddw_init(void)
 {
     spapr_rtas_register(RTAS_IBM_QUERY_PE_DMA_WINDOW,
@@ -292,6 +327,11 @@ static void spapr_rtas_ddw_init(void)
     spapr_rtas_register(RTAS_IBM_RESET_PE_DMA_WINDOW,
                         "ibm,reset-pe-dma-window",
                         rtas_ibm_reset_pe_dma_window);
+
+    spapr_rtas_register_wrong_endian(RTAS_IBM_QUERY_PE_DMA_WINDOW,
+                                     rtas_ibm_query_pe_dma_window_wrong_endian);
+    spapr_rtas_register_wrong_endian(RTAS_IBM_CREATE_PE_DMA_WINDOW,
+                                     rtas_ibm_create_pe_dma_window_wrong_endian);
 }
 
 type_init(spapr_rtas_ddw_init)
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 5f4e137..bf8e4a6 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -435,6 +435,8 @@ typedef void (*spapr_rtas_fn)(PowerPCCPU *cpu, sPAPREnvironment *spapr,
                               uint32_t nargs, target_ulong args,
                               uint32_t nret, target_ulong rets);
 void spapr_rtas_register(int token, const char *name, spapr_rtas_fn fn);
+void spapr_rtas_register_wrong_endian(int token, spapr_rtas_fn fn);
+
 target_ulong spapr_rtas_call(PowerPCCPU *cpu, sPAPREnvironment *spapr,
                              uint32_t token, uint32_t nargs, target_ulong args,
                              uint32_t nret, target_ulong rets);
-- 
2.0.0