On Thu, 18 Feb 2021 12:18:38 +0000
Alexandru Elisei [off-list ref] wrote:

Hi Andre,

On 2/17/21 4:48 PM, Alexandru Elisei wrote:

quoted

Hi Andre,

On 12/10/20 2:29 PM, Andre Przywara wrote:  

quoted

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 <redacted>  

I gave it more thought and I think I spoke too soon. I think it would be good to
document in the commit message how you came to the base MMIO address and size
(even if it was just a nice looking number). Also, the CFI flash device has its
memory range described in the memory layout for the architecture, in
arm/include/arm-common/kvm-arch.h. I think it would be a good idea to put the
serial region there, to prevent regressions in the future.

Yes, that's very true, the memory map should be described in one place
only. Will try to do that.

I did the math to make sure there's no overlap with the ioport region (16M >> 16K)
or the flash region (16M + 0x4000 < 32M). I also tested the changes with a kernel
with 4K and 64K pages (I can't access any hardware with 16K pages at the moment),
and everything worked as expected.

Thanks!
Andre

quoted

quoted

+#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);  

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