[RFC PATCH 4/8] ppc/spapr: add VTY backend support to OF read/write/open services

[uverma@linux.ibm.com]

From: Utkarsh Verma <uverma@linux.ibm.com>

Extend the VOF client interface to support console I/O through the sPAPR VTY
device, which is needed by bootloaders such as GRUB during disk boot.

Add vof_read() to implement the OpenFirmware "read" client service, which was
previously missing.

Route the OF read and write services backed by vty_getchars() and vty_putchars()

Make vty_getchars() public similar to vty_putchars().

AI-used-for: code
Signed-off-by: Utkarsh Verma <uverma@linux.ibm.com>
---
 hw/char/spapr_vty.c        |  2 +-
 hw/ppc/spapr_vof.c         |  2 +
 hw/ppc/trace-events        |  2 +
 hw/ppc/vof.c               | 84 ++++++++++++++++++++++++++++++++++++++
 include/hw/ppc/spapr_vio.h |  1 +
 5 files changed, 90 insertions(+), 1 deletion(-)

diff --git a/hw/char/spapr_vty.c b/hw/char/spapr_vty.c
index 1dd9fb155c..2c97e0e027 100644
--- a/hw/char/spapr_vty.c
+++ b/hw/char/spapr_vty.c
@@ -52,7 +52,7 @@ static void vty_receive(void *opaque, const uint8_t *buf, int size)
     }
 }
 
-static int vty_getchars(SpaprVioDevice *sdev, uint8_t *buf, int max)
+int vty_getchars(SpaprVioDevice *sdev, uint8_t *buf, int max)
 {
     SpaprVioVty *dev = VIO_SPAPR_VTY_DEVICE(sdev);
     int n = 0;
diff --git a/hw/ppc/spapr_vof.c b/hw/ppc/spapr_vof.c
index 5bf9613005..a08d45c6a5 100644
--- a/hw/ppc/spapr_vof.c
+++ b/hw/ppc/spapr_vof.c
@@ -74,6 +74,8 @@ void spapr_vof_client_dt_finalize(SpaprMachineState *spapr, void *fdt)
     if (stdout_path) {
         _FDT(vof_client_open_store(fdt, spapr->vof, "/chosen", "stdout",
                                    stdout_path));
+        _FDT(vof_client_open_store(fdt, spapr->vof, "/chosen", "stdin",
+                                   stdout_path));
     }
 }
 
diff --git a/hw/ppc/trace-events b/hw/ppc/trace-events
index 1f125ce841..dbdcfada26 100644
--- a/hw/ppc/trace-events
+++ b/hw/ppc/trace-events
@@ -79,6 +79,7 @@ vof_error_unknown_method(const char *method) "\"%s\""
 vof_error_unknown_ihandle_close(uint32_t ih) "ih=0x%x"
 vof_error_unknown_path(const char *path) "\"%s\""
 vof_error_write(uint32_t ih) "ih=0x%x"
+vof_error_read(uint32_t ih) "ih=0x%x"
 vof_finddevice(const char *path, uint32_t ph) "\"%s\" => ph=0x%x"
 vof_claim(uint32_t virt, uint32_t size, uint32_t align, uint32_t ret) "virt=0x%x size=0x%x align=0x%x => 0x%x"
 vof_release(uint32_t virt, uint32_t size, uint32_t ret) "virt=0x%x size=0x%x => 0x%x"
@@ -92,6 +93,7 @@ vof_package_to_path(uint32_t ph, const char *tmp, int ret) "ph=0x%x => %s len=%d
 vof_instance_to_path(uint32_t ih, uint32_t ph, const char *tmp, int ret) "ih=0x%x ph=0x%x => %s len=%d"
 vof_instance_to_package(uint32_t ih, uint32_t ph) "ih=0x%x => ph=0x%x"
 vof_write(uint32_t ih, unsigned cb, const char *msg) "ih=0x%x [%u] \"%s\""
+vof_read(uint32_t ih, unsigned cb, const char *msg) "ih=0x%x [%u] \"%s\""
 vof_avail(uint64_t start, uint64_t end, uint64_t size) "0x%"PRIx64"..0x%"PRIx64" size=0x%"PRIx64
 vof_claimed(uint64_t start, uint64_t end, uint64_t size) "0x%"PRIx64"..0x%"PRIx64" size=0x%"PRIx64
 
diff --git a/hw/ppc/vof.c b/hw/ppc/vof.c
index a78bb1f116..45c197df9f 100644
--- a/hw/ppc/vof.c
+++ b/hw/ppc/vof.c
@@ -9,6 +9,7 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include CONFIG_DEVICES /* CONFIG_PSERIES */
 #include "qemu/osdep.h"
 #include "qemu/timer.h"
 #include "qemu/range.h"
@@ -22,6 +23,7 @@
 #include "qom/qom-qobject.h"
 #include "trace.h"
 
+#include "hw/ppc/spapr_vio.h"
 #include <libfdt.h>
 
 /*
@@ -44,6 +46,7 @@ typedef struct {
 typedef struct {
     char *path; /* the path used to open the instance */
     uint32_t phandle;
+    void *vty;
 } OfInstance;
 
 static int readstr(hwaddr pa, char *buf, int size)
@@ -458,6 +461,28 @@ static uint32_t vof_do_open(void *fdt, Vof *vof, int offset, const char *path)
     ++vof->of_instance_last;
 
     inst->path = g_strdup(path);
+    inst->vty = NULL;
+
+#ifdef CONFIG_PSERIES
+    const char *node_name = fdt_get_name(fdt, offset, NULL);
+    if (node_name && strncmp(node_name, "vty", 3) == 0) {
+        uint8_t discard_buf[VOF_VTY_BUF_SIZE];
+        MachineState *ms = MACHINE(qdev_get_machine());
+        SpaprMachineState *spapr = SPAPR_MACHINE(ms);
+
+        if (spapr && spapr->vio_bus) {
+            inst->vty = spapr_vty_get_default(spapr->vio_bus);
+            if (inst->vty) {
+                /* Flush any stale data from the VTY input buffer */
+                while (vty_getchars(inst->vty, discard_buf,
+                                    sizeof(discard_buf)) > 0) {
+                    /* discard */
+                }
+            }
+        }
+    }
+#endif
+
     g_hash_table_insert(vof->of_instances,
                         GINT_TO_POINTER(vof->of_instance_last),
                         inst);
@@ -576,6 +601,23 @@ static uint32_t vof_write(Vof *vof, uint32_t ihandle, uint32_t buf,
         return PROM_ERROR;
     }
 
+#ifdef CONFIG_PSERIES
+    if (inst->vty) {
+        uint32_t total_written = 0;
+
+        for ( ; len > 0; len -= cb) {
+            cb = MIN(len, sizeof(tmp));
+            if (VOF_MEM_READ(buf, tmp, cb) != MEMTX_OK) {
+                return PROM_ERROR;
+            }
+            vty_putchars(inst->vty, (uint8_t *)tmp, cb);
+            buf += cb;
+            total_written += cb;
+        }
+        return total_written;
+    }
+#endif
+
     for ( ; len > 0; len -= cb) {
         cb = MIN(len, sizeof(tmp) - 1);
         if (VOF_MEM_READ(buf, tmp, cb) != MEMTX_OK) {
@@ -593,6 +635,46 @@ static uint32_t vof_write(Vof *vof, uint32_t ihandle, uint32_t buf,
     return len;
 }
 
+static uint32_t vof_read(Vof *vof, uint32_t ihandle, uint32_t buf,
+                         uint32_t len)
+{
+    OfInstance *inst = (OfInstance *)
+        g_hash_table_lookup(vof->of_instances, GINT_TO_POINTER(ihandle));
+
+    if (!inst) {
+        trace_vof_error_read(ihandle);
+        return PROM_ERROR;
+    }
+
+#ifdef CONFIG_PSERIES
+    if (inst->vty) {
+        uint8_t tmp[VOF_VTY_BUF_SIZE];
+        unsigned cb = MIN(len, sizeof(tmp));
+        uint32_t bytes_read = vty_getchars(inst->vty, tmp, cb);
+        if (bytes_read > 0) {
+            if (VOF_MEM_WRITE(buf, tmp, bytes_read) != MEMTX_OK) {
+                trace_vof_error_read(ihandle);
+                return PROM_ERROR;
+            }
+        }
+        if (trace_event_get_state(TRACE_VOF_READ) &&
+            qemu_loglevel_mask(LOG_TRACE)) {
+            char trace_buf[VOF_VTY_BUF_SIZE + 1];
+            memcpy(trace_buf, tmp, bytes_read);
+            trace_buf[bytes_read] = '\0';
+            trace_vof_read(ihandle, bytes_read, trace_buf);
+        }
+        return bytes_read;
+    }
+#endif
+
+    /*
+     * For other devices, return 0 to indicate no data available.
+     * This allows GRUB to continue without blocking on input.
+     */
+    return 0;
+}
+
 static void vof_claimed_dump(GArray *claimed)
 {
     int i;
@@ -905,6 +987,8 @@ static uint32_t vof_client_handle(MachineState *ms, void *fdt, Vof *vof,
         ret = vof_instance_to_path(fdt, vof, args[0], args[1], args[2]);
     } else if (cmpserv("write", 3, 1)) {
         ret = vof_write(vof, args[0], args[1], args[2]);
+    } else if (cmpserv("read", 3, 1)) {
+        ret = vof_read(vof, args[0], args[1], args[2]);
     } else if (cmpserv("claim", 3, 1)) {
         uint64_t ret64 = vof_claim(vof, args[0], args[1], args[2]);
 
diff --git a/include/hw/ppc/spapr_vio.h b/include/hw/ppc/spapr_vio.h
index 0ea0dbae8b..81e7c0b91b 100644
--- a/include/hw/ppc/spapr_vio.h
+++ b/include/hw/ppc/spapr_vio.h
@@ -136,6 +136,7 @@ static inline int spapr_vio_dma_set(SpaprVioDevice *dev, uint64_t taddr,
 int spapr_vio_send_crq(SpaprVioDevice *dev, uint8_t *crq);
 
 SpaprVioDevice *vty_lookup(SpaprMachineState *spapr, target_ulong reg);
+int vty_getchars(SpaprVioDevice *sdev, uint8_t *buf, int max);
 void vty_putchars(SpaprVioDevice *sdev, uint8_t *buf, int len);
 void spapr_vty_create(SpaprVioBus *bus, Chardev *chardev);
 void spapr_vlan_create(SpaprVioBus *bus, NICInfo *nd);
-- 
2.54.0