Re: [PATCH kvmtool 02/21] hw/serial: Use device abstraction for FDT generator function

Alexandru Elisei
2021-02-11T12:10:01Z

Hi Andre,

On 12/10/20 2:28 PM, Andre Przywara wrote:
> At the moment we use the .generate_fdt_node member of the ioport ops
> structure to store the function pointer for the FDT node generator
> function. ioport__register() will then put a wrapper and this pointer
> into the device header.
> The serial device is the only device making use of this special ioport
> feature, so let's move this over to using the device header directly.
>
> This will allow us to get rid of this .generate_fdt_node member in the
> ops and simplify the code.
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> hw/serial.c | 49 +++++++++++++++++++++++++++++++++++++----------
> include/kvm/kvm.h | 2 ++
> 2 files changed, 41 insertions(+), 10 deletions(-)
>
> diff --git a/hw/serial.c b/hw/serial.c
> index 13c4663e..b0465d99 100644
> --- a/hw/serial.c
> +++ b/hw/serial.c
> @@ -23,6 +23,7 @@
> #define UART_IIR_TYPE_BITS 0xc0
>
> struct serial8250_device {
> + struct device_header dev_hdr;
> struct mutex mutex;
> u8 id;
>
> @@ -53,9 +54,20 @@ struct serial8250_device {
> .msr = UART_MSR_DCD | UART_MSR_DSR | UART_MSR_CTS, \
> .mcr = UART_MCR_OUT2,
>
> +#ifdef CONFIG_HAS_LIBFDT
> +static
> +void serial8250_generate_fdt_node(void *fdt, struct device_header *dev_hdr,
> + fdt_irq_fn irq_fn);
> +#else
> +#define serial8250_generate_fdt_node NULL
> +#endif
> static struct serial8250_device devices[] = {
> /* ttyS0 */
> [0] = {
> + .dev_hdr = {
> + .bus_type = DEVICE_BUS_IOPORT,
> + .data = serial8250_generate_fdt_node,
> + },
> .mutex = MUTEX_INITIALIZER,
>
> .id = 0,
> @@ -66,6 +78,10 @@ static struct serial8250_device devices[] = {
> },
> /* ttyS1 */
> [1] = {
> + .dev_hdr = {
> + .bus_type = DEVICE_BUS_IOPORT,
> + .data = serial8250_generate_fdt_node,
> + },
> .mutex = MUTEX_INITIALIZER,
>
> .id = 1,
> @@ -76,6 +92,10 @@ static struct serial8250_device devices[] = {
> },
> /* ttyS2 */
> [2] = {
> + .dev_hdr = {
> + .bus_type = DEVICE_BUS_IOPORT,
> + .data = serial8250_generate_fdt_node,
> + },
> .mutex = MUTEX_INITIALIZER,
>
> .id = 2,
> @@ -86,6 +106,10 @@ static struct serial8250_device devices[] = {
> },
> /* ttyS3 */
> [3] = {
> + .dev_hdr = {
> + .bus_type = DEVICE_BUS_IOPORT,
> + .data = serial8250_generate_fdt_node,
> + },
> .mutex = MUTEX_INITIALIZER,
>
> .id = 3,
> @@ -371,13 +395,14 @@ char *fdt_stdout_path = NULL;
>
> #define DEVICE_NAME_MAX_LEN 32
> static
> -void serial8250_generate_fdt_node(struct ioport *ioport, void *fdt,
> - void (*generate_irq_prop)(void *fdt,
> - u8 irq,
> - enum irq_type))
> +void serial8250_generate_fdt_node(void *fdt, struct device_header *dev_hdr,
> + fdt_irq_fn irq_fn)
> {
> char dev_name[DEVICE_NAME_MAX_LEN];
> - struct serial8250_device *dev = ioport->priv;
> + struct serial8250_device *dev = container_of(dev_hdr,
> + struct serial8250_device,
> + dev_hdr);
> +
> u64 addr = KVM_IOPORT_AREA + dev->iobase;
> u64 reg_prop[] = {
> cpu_to_fdt64(addr),
> @@ -395,24 +420,26 @@ void serial8250_generate_fdt_node(struct ioport *ioport, void *fdt,
> _FDT(fdt_begin_node(fdt, dev_name));
> _FDT(fdt_property_string(fdt, "compatible", "ns16550a"));
> _FDT(fdt_property(fdt, "reg", reg_prop, sizeof(reg_prop)));
> - generate_irq_prop(fdt, dev->irq, IRQ_TYPE_LEVEL_HIGH);
> + irq_fn(fdt, dev->irq, IRQ_TYPE_LEVEL_HIGH);
> _FDT(fdt_property_cell(fdt, "clock-frequency", 1843200));
> _FDT(fdt_end_node(fdt));
> }
> -#else
> -#define serial8250_generate_fdt_node NULL
> #endif
>
> static struct ioport_operations serial8250_ops = {
> .io_in = serial8250_in,
> .io_out = serial8250_out,
> - .generate_fdt_node = serial8250_generate_fdt_node,
> };
>
> -static int serial8250__device_init(struct kvm *kvm, struct serial8250_device *dev)
> +static int serial8250__device_init(struct kvm *kvm,
> + struct serial8250_device *dev)
> {
> int r;
>
> + r = device__register(&dev->dev_hdr);
> + if (r < 0)
> + return r;
> +
> ioport__map_irq(&dev->irq);
> r = ioport__register(kvm, dev->iobase, &serial8250_ops, 8, dev);

It's unfortunate that we now create two devices for one serial instance: one here,
and one created by ioport__register(). But I guess that's unavoidable in this
patch, and later patches will remove it.

>
> @@ -438,6 +465,7 @@ cleanup:
> struct serial8250_device *dev = &devices[j];
>
> ioport__unregister(kvm, dev->iobase);
> + device__unregister(&dev->dev_hdr);
> }
>
> return r;
> @@ -455,6 +483,7 @@ int serial8250__exit(struct kvm *kvm)
> r = ioport__unregister(kvm, dev->iobase);
> if (r < 0)
> return r;
> + device__unregister(&dev->dev_hdr);
> }
>
> return 0;
> diff --git a/include/kvm/kvm.h b/include/kvm/kvm.h
> index 53373b08..ee99c28e 100644
> --- a/include/kvm/kvm.h
> +++ b/include/kvm/kvm.h
> @@ -31,6 +31,8 @@
> .name = #ext, \
> .code = ext
>
> +typedef void (*fdt_irq_fn)(void *fdt, u8 irq, enum irq_type);

Shouldn't that last parameter be enum irq_type irq_type? Would you consider moving
the typedef to include/kvm/fdt.h?

Other than the nitpicks above, the patch looks sound to me. I also did a quick
test by running kvm-unit-tests:

Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>

Thanks,
Alex
> +
> enum {
> KVM_VMSTATE_RUNNING,
> KVM_VMSTATE_PAUSED,