Hi Balaton,
Thank you for the review.

On 10/7/26 8:05 PM, BALATON Zoltan wrote:
On Fri, 2 Oct 2026, [email protected] wrote:
From: Utkarsh Verma <[email protected]>

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 <[email protected]>
---
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 78d5b7d5b5..3195c859a4 100644
--- a/hw/ppc/spapr_vof.c
+++ b/hw/ppc/spapr_vof.c
@@ -76,6 +76,8 @@ 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 9ad1aa7626..6f6d424347 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/ctype.h"
#include "qemu/timer.h"
@@ -23,6 +24,7 @@
#include "qom/qom-qobject.h"
#include "trace.h"

+#include "hw/ppc/spapr_vio.h"
#include <libfdt.h>

/*
@@ -45,6 +47,7 @@ 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)
@@ -459,6 +462,28 @@ 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);
@@ -577,6 +602,23 @@ 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
+

Instead of adding #ifdefs in this file could these be implemented as some functions exported by spapr_vof.c and called here without needing #ifdefs? Maybe it could be part of VofMachineIfClass similar to setprop.

Agreed. In v3 I will add new callbacks in VofMachineIfClass for vty_open, vty_read and vty_write and implement all those in spapr_vof.c and just call the hook from here without needing any ifdefs.

Regards,
BALATON Zoltan

    for ( ; len > 0; len -= cb) {
        cb = MIN(len, sizeof(tmp) - 1);
        if (VOF_MEM_READ(buf, tmp, cb) != MEMTX_OK) {
@@ -594,6 +636,46 @@ 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;
@@ -906,6 +988,8 @@ 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);



Regards,
Utkarsh


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