Hi Andre,

On 2/18/21 2:41 PM, Andre Przywara wrote:

On Tue, 16 Feb 2021 14:22:05 +0000
Alexandru Elisei [off-list ref] wrote:

quoted

Hi Andre,

Patch looks good, nitpicks below.

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

quoted

With the planned retirement of the special ioport emulation code, we
need to provide an emulation function compatible with the MMIO prototype.

Adjust the trap handler to use that new function, and provide shims to
implement the old ioport interface, for now.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 hw/serial.c | 97 +++++++++++++++++++++++++++++++++++------------------
 1 file changed, 65 insertions(+), 32 deletions(-)

diff --git a/hw/serial.c b/hw/serial.c
index b0465d99..2907089c 100644
--- a/hw/serial.c
+++ b/hw/serial.c

@@ -242,36 +242,31 @@ void serial8250__inject_sysrq(struct kvm *kvm, char sysrq)
 	sysrq_pending = sysrq;
 }
 
-static bool serial8250_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port,
-			   void *data, int size)
+static bool serial8250_out(struct serial8250_device *dev, struct kvm_cpu *vcpu,
+			   u16 offset, u8 data)
 {
-	struct serial8250_device *dev = ioport->priv;
-	u16 offset;
 	bool ret = true;
-	char *addr = data;
 
 	mutex_lock(&dev->mutex);
 
-	offset = port - dev->iobase;
-
 	switch (offset) {
 	case UART_TX:
 		if (dev->lcr & UART_LCR_DLAB) {
-			dev->dll = ioport__read8(data);
+			dev->dll = data;
 			break;
 		}
 
 		/* Loopback mode */
 		if (dev->mcr & UART_MCR_LOOP) {
 			if (dev->rxcnt < FIFO_LEN) {
-				dev->rxbuf[dev->rxcnt++] = *addr;
+				dev->rxbuf[dev->rxcnt++] = data;
 				dev->lsr |= UART_LSR_DR;
 			}
 			break;
 		}
 
 		if (dev->txcnt < FIFO_LEN) {
-			dev->txbuf[dev->txcnt++] = *addr;
+			dev->txbuf[dev->txcnt++] = data;
 			dev->lsr &= ~UART_LSR_TEMT;
 			if (dev->txcnt == FIFO_LEN / 2)
 				dev->lsr &= ~UART_LSR_THRE;

@@ -283,18 +278,18 @@ static bool serial8250_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port
 		break;
 	case UART_IER:
 		if (!(dev->lcr & UART_LCR_DLAB))
-			dev->ier = ioport__read8(data) & 0x0f;
+			dev->ier = data & 0x0f;
 		else
-			dev->dlm = ioport__read8(data);
+			dev->dlm = data;
 		break;
 	case UART_FCR:
-		dev->fcr = ioport__read8(data);
+		dev->fcr = data;
 		break;
 	case UART_LCR:
-		dev->lcr = ioport__read8(data);
+		dev->lcr = data;
 		break;
 	case UART_MCR:
-		dev->mcr = ioport__read8(data);
+		dev->mcr = data;
 		break;
 	case UART_LSR:
 		/* Factory test */

@@ -303,7 +298,7 @@ static bool serial8250_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port
 		/* Not used */
 		break;
 	case UART_SCR:
-		dev->scr = ioport__read8(data);
+		dev->scr = data;
 		break;
 	default:
 		ret = false;

@@ -336,46 +331,43 @@ static void serial8250_rx(struct serial8250_device *dev, void *data)
 	}
 }
 
-static bool serial8250_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
+static bool serial8250_in(struct serial8250_device *dev, struct kvm_cpu *vcpu,
+			  u16 offset, u8 *data)
 {
-	struct serial8250_device *dev = ioport->priv;
-	u16 offset;
 	bool ret = true;
 
 	mutex_lock(&dev->mutex);
 
-	offset = port - dev->iobase;
-
 	switch (offset) {
 	case UART_RX:
 		if (dev->lcr & UART_LCR_DLAB)
-			ioport__write8(data, dev->dll);
+			*data = dev->dll;
 		else
 			serial8250_rx(dev, data);
 		break;
 	case UART_IER:
 		if (dev->lcr & UART_LCR_DLAB)
-			ioport__write8(data, dev->dlm);
+			*data = dev->dlm;
 		else
-			ioport__write8(data, dev->ier);
+			*data = dev->ier;
 		break;
 	case UART_IIR:
-		ioport__write8(data, dev->iir | UART_IIR_TYPE_BITS);
+		*data = dev->iir | UART_IIR_TYPE_BITS;
 		break;
 	case UART_LCR:
-		ioport__write8(data, dev->lcr);
+		*data = dev->lcr;
 		break;
 	case UART_MCR:
-		ioport__write8(data, dev->mcr);
+		*data = dev->mcr;
 		break;
 	case UART_LSR:
-		ioport__write8(data, dev->lsr);
+		*data = dev->lsr;
 		break;
 	case UART_MSR:
-		ioport__write8(data, dev->msr);
+		*data = dev->msr;
 		break;
 	case UART_SCR:
-		ioport__write8(data, dev->scr);
+		*data = dev->scr;
 		break;
 	default:
 		ret = false;

@@ -389,6 +381,47 @@ static bool serial8250_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port,
 	return ret;
 }
 
+static void serial8250_mmio(struct kvm_cpu *vcpu, u64 addr, u8 *data, u32 len,
+			    u8 is_write, void *ptr)
+{
+	struct serial8250_device *dev = ptr;
+	u8 value = 0;
+
+	if (is_write) {
+		 value = *data;  

Extra space before value.

quoted

+
+		serial8250_out(dev, vcpu, addr - dev->iobase, value);
+	} else {
+		if (serial8250_in(dev, vcpu, addr - dev->iobase, &value))
+			*data = value;
+	}
+}
+
+static bool serial8250_ioport_out(struct ioport *ioport, struct kvm_cpu *vcpu,
+				  u16 port, void *data, int size)
+{
+	struct serial8250_device *dev = ioport->priv;
+	u8 value = ioport__read8(data);
+
+	serial8250_mmio(vcpu, port, &value, 1, true, dev);
+
+	return true;
+}
+
+static bool serial8250_ioport_in(struct ioport *ioport, struct kvm_cpu *vcpu,
+				 u16 port, void *data, int size)
+{
+	struct serial8250_device *dev = ioport->priv;
+	u8 value = 0;
+
+
+	serial8250_mmio(vcpu, port, &value, 1, false, dev);
+
+	ioport__write8(data, value);  

This is correct, but confusing. You pass the address of a local variable as *data
to serial8250_mmio, serial8250_mmio conditionally updates the value at data (which
is &value from here), and then here we update the *data unconditionally. Why not
pass data directly to serial8250_mmio and skip the local variable? Am I missing
something?

The idea is to keep the abstraction of ioport__write<x>. I agree this
is somewhat pointless for a single byte write, since the purpose of
those wrappers is to deal with endianness, but it seems nice to use
that anyway, anywhere, in case we need to add something to the wrappers
at some point.

What I was thinking was something like this:

@@ -385,25 +386,19 @@ static void serial8250_mmio(struct kvm_cpu *vcpu, u64 addr,

u8 *data, u32 len,
                            u8 is_write, void *ptr)
 {
        struct serial8250_device *dev = ptr;
-       u8 value = 0;
 
-       if (is_write) {
-                value = *data;
-
-               serial8250_out(dev, vcpu, addr - dev->iobase, value);
-       } else {
-               if (serial8250_in(dev, vcpu, addr - dev->iobase, &value))
-                       *data = value;
-       }
+       if (is_write)
+               serial8250_out(dev, vcpu, addr - dev->iobase, data);
+       else
+               serial8250_in(dev, vcpu, addr - dev->iobase, data);
 }
 
 static bool serial8250_ioport_out(struct ioport *ioport, struct kvm_cpu *vcpu,
                                  u16 port, void *data, int size)
 {
        struct serial8250_device *dev = ioport->priv;
-       u8 value = ioport__read8(data);
 
-       serial8250_mmio(vcpu, port, &value, 1, true, dev);
+       serial8250_mmio(vcpu, port, data, 1, true, dev);
 
        return true;
 }

@@ -412,12 +407,8 @@ static bool serial8250_ioport_in(struct ioport *ioport,

struct kvm_cpu *vcpu,
                                 u16 port, void *data, int size)
 {
        struct serial8250_device *dev = ioport->priv;
-       u8 value = 0;
-
-
-       serial8250_mmio(vcpu, port, &value, 1, false, dev);
 
-       ioport__write8(data, value);
+       serial8250_mmio(vcpu, port, data, 1, false, dev);
 
        return true;
 }

And the ioport_{read,write}8 function will used inside the serial8250_{out,in}
functions, like they were before this patch, which should also make the diff
smaller. Or is there something that I'm missing which makes this unfeasible?

Thanks,

Alex

ioport__write8() is a static inline in a header file, so it shouldn't
really hurt, the compiler is able to see through it. The generated code
is almost the same, at least.

Let me know what you think!

Cheers,
Andre

quoted

quoted

+
+	return true;
+}
+
 #ifdef CONFIG_HAS_LIBFDT
 
 char *fdt_stdout_path = NULL;

@@ -427,8 +460,8 @@ void serial8250_generate_fdt_node(void *fdt, struct device_header *dev_hdr,
 #endif
 
 static struct ioport_operations serial8250_ops = {
-	.io_in			= serial8250_in,
-	.io_out			= serial8250_out,
+	.io_in			= serial8250_ioport_in,
+	.io_out			= serial8250_ioport_out,
 };
 
 static int serial8250__device_init(struct kvm *kvm,