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

Andre Przywara
2020-12-10T19:02:58Z

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
+#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);
--
2.17.1