Re: [PATCH kvmtool 13/21] hw/serial: Refactor trap handler

Alexandru Elisei
2021-02-16T14:23:04Z

Hi Andre,

Patch looks good, nitpicks below.

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

> +
> + 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?

Thanks,

Alex

> +
> + 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,