Using QEMU how to redirect serial /dev/ttyS2 output of guest machine to host machine.

Using QEMU how to redirect serial /dev/ttyS2 output of guest machine to host machine.

[Abhishek Singh Dagur]

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Hi all,

We are using obmc-phosphor-image on an ast2500 board which is trying to
communicate with other devices over serial port /dev/ttyS2.
As we are trying to emulate the machine on qemu we need to redirect the
request to the host machine so that it can handle this request and return
appropriately.
We tried using QEMU options like -serial ,-chardev but still not the
concrete way we get to do it.

It will be very helpful if you can provide us some guidance on this.

Thank you,
Abhishek

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Re: Using QEMU how to redirect serial /dev/ttyS2 output of guest machine to host machine.

[Alex Bennée]

Abhishek Singh Dagur <abhishek@drut.io> writes:

(cc aspeed maintainers)

> Hi all,
>
> We are using obmc-phosphor-image on an ast2500 board which is trying to communicate with other devices
> over serial port /dev/ttyS2.
> As we are trying to emulate the machine on qemu we need to redirect the request to the host machine so
> that it can handle this request and return appropriately.
> We tried using QEMU options like -serial ,-chardev but still not the
> concrete way we get to do it.

Yeah I'm afraid its non-obvious, certainly for built in serial ports.
Try something like:

  ./qemu-system-aarch64 -M ast2500-evb \
    -serial null -serial null -serial chardev:myserial \
    -chardev file,id=myserial,path=output.txt \
    $MORE_OPTIONS

You have to add a -serial for each serial port up to the one you care
about and then set the chardev for it.

If you where adding a device to the system then you can explicitly set
the target chardev for it with something like:

  -device isa-serial,iobase=nnn,irq=nnn,chardev=ID

> It will be very helpful if you can provide us some guidance on this.

Another quirk for the aspeed boards seems to be the default uart can be
an arbitrary one depending on the board model:

334:    aspeed_soc_uart_set_chr(s, amc->uart_default, serial_hd(0)); 
336:        if (uart == amc->uart_default) {                         
1112:    amc->uart_default = ASPEED_DEV_UART5;                       
1407:    amc->uart_default = ASPEED_DEV_UART1;                       

as a result ASPEED_DEV_UART5 will always be the first serial port
(serial_hd(0)). I don't know how Linux numbers them but worth being
aware of.

>
> Thank you,
> Abhishek


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

Re: Using QEMU how to redirect serial /dev/ttyS2 output of guest machine to host machine.

[Cédric Le Goater]

On 3/17/23 17:06, Alex Bennée wrote:
> 
> Abhishek Singh Dagur <abhishek@drut.io> writes:
> 
> (cc aspeed maintainers)
> 
>> Hi all,
>>
>> We are using obmc-phosphor-image on an ast2500 board which is trying to communicate with other devices
>> over serial port /dev/ttyS2.
>> As we are trying to emulate the machine on qemu we need to redirect the request to the host machine so
>> that it can handle this request and return appropriately.
>> We tried using QEMU options like -serial ,-chardev but still not the
>> concrete way we get to do it.
> 
> Yeah I'm afraid its non-obvious, certainly for built in serial ports.
> Try something like:
> 
>    ./qemu-system-aarch64 -M ast2500-evb \
>      -serial null -serial null -serial chardev:myserial \
>      -chardev file,id=myserial,path=output.txt \
>      $MORE_OPTIONS
> 
> You have to add a -serial for each serial port up to the one you care
> about and then set the chardev for it.
> 
> If you where adding a device to the system then you can explicitly set
> the target chardev for it with something like:
> 
>    -device isa-serial,iobase=nnn,irq=nnn,chardev=ID
> 
>> It will be very helpful if you can provide us some guidance on this.
> 
> Another quirk for the aspeed boards seems to be the default uart can be
> an arbitrary one depending on the board model:
> 
> 334:    aspeed_soc_uart_set_chr(s, amc->uart_default, serial_hd(0));
> 336:        if (uart == amc->uart_default) {
> 1112:    amc->uart_default = ASPEED_DEV_UART5;
> 1407:    amc->uart_default = ASPEED_DEV_UART1;
> 
> as a result ASPEED_DEV_UART5 will always be the first serial port
> (serial_hd(0)). I don't know how Linux numbers them but worth being
> aware of.

Yes. UART5 is the general default but it depends on the board definition
and the fuji was the first to require an exception. See commit 5d63d0c76c
("hw/arm/aspeed: Allow machine to set UART default")

Then, it became more complex with commit d2b3eaefb4 ("aspeed: Refactor
UART init for multi-SoC machines"). That's another topic.

Abhishek,

I am afraid, you will need to add a new board to fit what's in the DT.

Or, here is a little patch adding a machine option to set the default uart.
It was never merged because it is a bit of hack, give it a try and we
will discuss. Use :

   -M ast2500-evb,uart-default=uart2


Thanks,

C.

 From 0d0700ae772fa5236914e96af1be5afcf0d4a994 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg@kaod.org>
Date: Fri, 17 Mar 2023 18:21:54 +0100
Subject: [PATCH] aspeed: Add a "uart-default" machine option
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
  hw/arm/aspeed.c | 31 +++++++++++++++++++++++++++++--
  1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
index 806bb10707..e0335cf167 100644
--- a/hw/arm/aspeed.c
+++ b/hw/arm/aspeed.c
@@ -45,6 +45,7 @@ struct AspeedMachineState {
      bool mmio_exec;
      char *fmc_model;
      char *spi_model;
+    uint32_t uart_default;
      uint32_t hw_strap1;
  };
  
@@ -337,10 +338,11 @@ static void connect_serial_hds_to_uarts(AspeedMachineState *bmc)
      AspeedMachineClass *amc = ASPEED_MACHINE_GET_CLASS(bmc);
      AspeedSoCState *s = &bmc->soc;
      AspeedSoCClass *sc = ASPEED_SOC_GET_CLASS(s);
+    int uart_default = bmc->uart_default ? bmc->uart_default : amc->uart_default;
  
-    aspeed_soc_uart_set_chr(s, amc->uart_default, serial_hd(0));
+    aspeed_soc_uart_set_chr(s, uart_default, serial_hd(0));
      for (int i = 1, uart = ASPEED_DEV_UART1; i < sc->uarts_num; i++, uart++) {
-        if (uart == amc->uart_default) {
+        if (uart == uart_default) {
              continue;
          }
          aspeed_soc_uart_set_chr(s, uart, serial_hd(i));
@@ -1145,6 +1147,25 @@ static void aspeed_set_spi_model(Object *obj, const char *value, Error **errp)
      bmc->spi_model = g_strdup(value);
  }
  
+const QEnumLookup UartDefault_lookup = {
+    .array =
+        (const char *const[]) {
+            [0] = "none",
+            [1] = "uart1",
+            [2] = "uart2",
+            [3] = "uart3",
+            [4] = "uart4",
+            [5] = "uart5",
+        },
+    .size = 6
+};
+
+static void aspeed_set_uart_default(Object *obj, int val, Error **err)
+{
+    AspeedMachineState *bmc = ASPEED_MACHINE(obj);
+    bmc->uart_default = val + 1;
+}
+
  static void aspeed_machine_class_props_init(ObjectClass *oc)
  {
      object_class_property_add_bool(oc, "execute-in-place",
@@ -1153,6 +1174,12 @@ static void aspeed_machine_class_props_init(ObjectClass *oc)
      object_class_property_set_description(oc, "execute-in-place",
                             "boot directly from CE0 flash device");
  
+    object_class_property_add_enum(oc, "uart-default", "UartDefault",
+                                   &UartDefault_lookup, NULL,
+                                   aspeed_set_uart_default);
+    object_class_property_set_description(oc, "uart-default",
+                           "Change the default UART of the board");
+
      object_class_property_add_str(oc, "fmc-model", aspeed_get_fmc_model,
                                     aspeed_set_fmc_model);
      object_class_property_set_description(oc, "fmc-model",
-- 
2.39.2

Re: Using QEMU how to redirect serial /dev/ttyS2 output of guest machine to host machine.

[Abhishek Singh Dagur]

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Thanks, I'll check it out.

On Fri, Mar 17, 2023 at 10:54 PM Cédric Le Goater <clg@kaod.org> wrote:

> On 3/17/23 17:06, Alex Bennée wrote:
> >
> > Abhishek Singh Dagur <abhishek@drut.io> writes:
> >
> > (cc aspeed maintainers)
> >
> >> Hi all,
> >>
> >> We are using obmc-phosphor-image on an ast2500 board which is trying to
> communicate with other devices
> >> over serial port /dev/ttyS2.
> >> As we are trying to emulate the machine on qemu we need to redirect the
> request to the host machine so
> >> that it can handle this request and return appropriately.
> >> We tried using QEMU options like -serial ,-chardev but still not the
> >> concrete way we get to do it.
> >
> > Yeah I'm afraid its non-obvious, certainly for built in serial ports.
> > Try something like:
> >
> >    ./qemu-system-aarch64 -M ast2500-evb \
> >      -serial null -serial null -serial chardev:myserial \
> >      -chardev file,id=myserial,path=output.txt \
> >      $MORE_OPTIONS
> >
> > You have to add a -serial for each serial port up to the one you care
> > about and then set the chardev for it.
> >
> > If you where adding a device to the system then you can explicitly set
> > the target chardev for it with something like:
> >
> >    -device isa-serial,iobase=nnn,irq=nnn,chardev=ID
> >
> >> It will be very helpful if you can provide us some guidance on this.
> >
> > Another quirk for the aspeed boards seems to be the default uart can be
> > an arbitrary one depending on the board model:
> >
> > 334:    aspeed_soc_uart_set_chr(s, amc->uart_default, serial_hd(0));
> > 336:        if (uart == amc->uart_default) {
> > 1112:    amc->uart_default = ASPEED_DEV_UART5;
> > 1407:    amc->uart_default = ASPEED_DEV_UART1;
> >
> > as a result ASPEED_DEV_UART5 will always be the first serial port
> > (serial_hd(0)). I don't know how Linux numbers them but worth being
> > aware of.
>
> Yes. UART5 is the general default but it depends on the board definition
> and the fuji was the first to require an exception. See commit 5d63d0c76c
> ("hw/arm/aspeed: Allow machine to set UART default")
>
> Then, it became more complex with commit d2b3eaefb4 ("aspeed: Refactor
> UART init for multi-SoC machines"). That's another topic.
>
> Abhishek,
>
> I am afraid, you will need to add a new board to fit what's in the DT.
>
> Or, here is a little patch adding a machine option to set the default uart.
> It was never merged because it is a bit of hack, give it a try and we
> will discuss. Use :
>
>    -M ast2500-evb,uart-default=uart2
>
>
> Thanks,
>
> C.
>
>  From 0d0700ae772fa5236914e96af1be5afcf0d4a994 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg@kaod.org>
> Date: Fri, 17 Mar 2023 18:21:54 +0100
> Subject: [PATCH] aspeed: Add a "uart-default" machine option
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
>   hw/arm/aspeed.c | 31 +++++++++++++++++++++++++++++--
>   1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
> index 806bb10707..e0335cf167 100644
> --- a/hw/arm/aspeed.c
> +++ b/hw/arm/aspeed.c
> @@ -45,6 +45,7 @@ struct AspeedMachineState {
>       bool mmio_exec;
>       char *fmc_model;
>       char *spi_model;
> +    uint32_t uart_default;
>       uint32_t hw_strap1;
>   };
>
> @@ -337,10 +338,11 @@ static void
> connect_serial_hds_to_uarts(AspeedMachineState *bmc)
>       AspeedMachineClass *amc = ASPEED_MACHINE_GET_CLASS(bmc);
>       AspeedSoCState *s = &bmc->soc;
>       AspeedSoCClass *sc = ASPEED_SOC_GET_CLASS(s);
> +    int uart_default = bmc->uart_default ? bmc->uart_default :
> amc->uart_default;
>
> -    aspeed_soc_uart_set_chr(s, amc->uart_default, serial_hd(0));
> +    aspeed_soc_uart_set_chr(s, uart_default, serial_hd(0));
>       for (int i = 1, uart = ASPEED_DEV_UART1; i < sc->uarts_num; i++,
> uart++) {
> -        if (uart == amc->uart_default) {
> +        if (uart == uart_default) {
>               continue;
>           }
>           aspeed_soc_uart_set_chr(s, uart, serial_hd(i));
> @@ -1145,6 +1147,25 @@ static void aspeed_set_spi_model(Object *obj, const
> char *value, Error **errp)
>       bmc->spi_model = g_strdup(value);
>   }
>
> +const QEnumLookup UartDefault_lookup = {
> +    .array =
> +        (const char *const[]) {
> +            [0] = "none",
> +            [1] = "uart1",
> +            [2] = "uart2",
> +            [3] = "uart3",
> +            [4] = "uart4",
> +            [5] = "uart5",
> +        },
> +    .size = 6
> +};
> +
> +static void aspeed_set_uart_default(Object *obj, int val, Error **err)
> +{
> +    AspeedMachineState *bmc = ASPEED_MACHINE(obj);
> +    bmc->uart_default = val + 1;
> +}
> +
>   static void aspeed_machine_class_props_init(ObjectClass *oc)
>   {
>       object_class_property_add_bool(oc, "execute-in-place",
> @@ -1153,6 +1174,12 @@ static void
> aspeed_machine_class_props_init(ObjectClass *oc)
>       object_class_property_set_description(oc, "execute-in-place",
>                              "boot directly from CE0 flash device");
>
> +    object_class_property_add_enum(oc, "uart-default", "UartDefault",
> +                                   &UartDefault_lookup, NULL,
> +                                   aspeed_set_uart_default);
> +    object_class_property_set_description(oc, "uart-default",
> +                           "Change the default UART of the board");
> +
>       object_class_property_add_str(oc, "fmc-model", aspeed_get_fmc_model,
>                                      aspeed_set_fmc_model);
>       object_class_property_set_description(oc, "fmc-model",
> --
> 2.39.2
>
>
>

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