Re: [PATCH kvmtool 20/21] hw/serial: ARM/arm64: Use MMIO at higher addresses

Alexandru Elisei
2021-02-17T16:49:57Z

Hi Andre,

On 12/10/20 2:29 PM, Andre Przywara wrote:
> Using the UART devices at their legacy I/O addresses as set by IBM in
> 1981 was a kludge we used for simplicity on ARM platforms as well.
> However this imposes problems due to their missing alignment and overlap
> with the PCI I/O address space.
>
> Now that we can switch a device easily between using ioports and MMIO,
> let's move the UARTs out of the first 4K of memory on ARM platforms.
>
> That should be transparent for well behaved guests, since the change is
> naturally reflected in the device tree. Even "earlycon" keeps working,
> as the stdout-path property is adjusted automatically.
>
> People providing direct earlycon parameters via the command line need to
> adjust it to: "earlycon=uart,mmio,0x1000000".
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> hw/serial.c | 52 ++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 36 insertions(+), 16 deletions(-)
>
> diff --git a/hw/serial.c b/hw/serial.c
> index d840eebc..00fb3aa8 100644
> --- a/hw/serial.c
> +++ b/hw/serial.c
> @@ -13,6 +13,24 @@
>
> #include <pthread.h>
>
> +#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
> +#define serial_iobase(nr) (0x1000000 + (nr) * 0x1000)
> +#define serial_irq(nr) (32 + (nr))
> +#define SERIAL8250_BUS_TYPE DEVICE_BUS_MMIO
> +#else
> +#define serial_iobase_0 0x3f8
> +#define serial_iobase_1 0x2f8
> +#define serial_iobase_2 0x3e8
> +#define serial_iobase_3 0x2e8
> +#define serial_irq_0 4
> +#define serial_irq_1 3
> +#define serial_irq_2 4
> +#define serial_irq_3 3

Nitpick: serial_iobase_* and serial_irq_* could be changed to have two leading
underscores, to stress the fact that they are helpers for serial_iobase() and
serial_irq() and are not meant to be used by themselves. But that's just personal
preference, otherwise the patch looks really nice and clean:

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

Thanks,

Alex

> +#define serial_iobase(nr) serial_iobase_##nr
> +#define serial_irq(nr) serial_irq_##nr
> +#define SERIAL8250_BUS_TYPE DEVICE_BUS_IOPORT
> +#endif
> +
> /*
> * This fakes a U6_16550A. The fifo len needs to be 64 as the kernel
> * expects that for autodetection.
> @@ -27,7 +45,7 @@ struct serial8250_device {
> struct mutex mutex;
> u8 id;
>
> - u16 iobase;
> + u32 iobase;
> u8 irq;
> u8 irq_state;
> int txcnt;
> @@ -65,56 +83,56 @@ static struct serial8250_device devices[] = {
> /* ttyS0 */
> [0] = {
> .dev_hdr = {
> - .bus_type = DEVICE_BUS_IOPORT,
> + .bus_type = SERIAL8250_BUS_TYPE,
> .data = serial8250_generate_fdt_node,
> },
> .mutex = MUTEX_INITIALIZER,
>
> .id = 0,
> - .iobase = 0x3f8,
> - .irq = 4,
> + .iobase = serial_iobase(0),
> + .irq = serial_irq(0),
>
> SERIAL_REGS_SETTING
> },
> /* ttyS1 */
> [1] = {
> .dev_hdr = {
> - .bus_type = DEVICE_BUS_IOPORT,
> + .bus_type = SERIAL8250_BUS_TYPE,
> .data = serial8250_generate_fdt_node,
> },
> .mutex = MUTEX_INITIALIZER,
>
> .id = 1,
> - .iobase = 0x2f8,
> - .irq = 3,
> + .iobase = serial_iobase(1),
> + .irq = serial_irq(1),
>
> SERIAL_REGS_SETTING
> },
> /* ttyS2 */
> [2] = {
> .dev_hdr = {
> - .bus_type = DEVICE_BUS_IOPORT,
> + .bus_type = SERIAL8250_BUS_TYPE,
> .data = serial8250_generate_fdt_node,
> },
> .mutex = MUTEX_INITIALIZER,
>
> .id = 2,
> - .iobase = 0x3e8,
> - .irq = 4,
> + .iobase = serial_iobase(2),
> + .irq = serial_irq(2),
>
> SERIAL_REGS_SETTING
> },
> /* ttyS3 */
> [3] = {
> .dev_hdr = {
> - .bus_type = DEVICE_BUS_IOPORT,
> + .bus_type = SERIAL8250_BUS_TYPE,
> .data = serial8250_generate_fdt_node,
> },
> .mutex = MUTEX_INITIALIZER,
>
> .id = 3,
> - .iobase = 0x2e8,
> - .irq = 3,
> + .iobase = serial_iobase(3),
> + .irq = serial_irq(3),
>
> SERIAL_REGS_SETTING
> },
> @@ -444,7 +462,8 @@ static int serial8250__device_init(struct kvm *kvm,
> return r;
>
> ioport__map_irq(&dev->irq);
> - r = kvm__register_pio(kvm, dev->iobase, 8, serial8250_mmio, dev);
> + r = kvm__register_iotrap(kvm, dev->iobase, 8, serial8250_mmio, dev,
> + SERIAL8250_BUS_TYPE);
>
> return r;
> }
> @@ -467,7 +486,7 @@ cleanup:
> for (j = 0; j <= i; j++) {
> struct serial8250_device *dev = &devices[j];
>
> - kvm__deregister_pio(kvm, dev->iobase);
> + kvm__deregister_iotrap(kvm, dev->iobase, SERIAL8250_BUS_TYPE);
> device__unregister(&dev->dev_hdr);
> }
>
> @@ -483,7 +502,8 @@ int serial8250__exit(struct kvm *kvm)
> for (i = 0; i < ARRAY_SIZE(devices); i++) {
> struct serial8250_device *dev = &devices[i];
>
> - r = kvm__deregister_pio(kvm, dev->iobase);
> + r = kvm__deregister_iotrap(kvm, dev->iobase,
> + SERIAL8250_BUS_TYPE);
> if (r < 0)
> return r;
> device__unregister(&dev->dev_hdr);