Re: [Xen-devel] [PATCH v5 21/25] xen: support console_switching between Dom0 and DomUs on ARM

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

On 10/23/2018 05:03 AM, Stefano Stabellini wrote:
> Today Ctrl-AAA is used to switch between Xen and Dom0. Extend the
> mechanism to allow for switching between Xen, Dom0, and any of the
> initial DomU created from Xen alongside Dom0 out of information provided
> via device tree.
>
> Rename xen_rx to console_rx to match the new behavior.
>
> Clarify existing comment about "notify the guest", making it clear that
> it is only about the hardware domain.
>
> Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
> CC: andrew.cooper3@xxxxxxxxxx
> CC: George.Dunlap@xxxxxxxxxxxxx
> CC: ian.jackson@xxxxxxxxxxxxx
> CC: jbeulich@xxxxxxxx
> CC: konrad.wilk@xxxxxxxxxx
> CC: tim@xxxxxxx
> CC: wei.liu2@xxxxxxxxxx
> ---
> Changes in v5:
> - move patch earlier and disable code that calls vpl011_rx_char_xen (not
>    defined yet)
> - improve comments
> - replace ifs with a switch
> - code style
>
> Changes in v4:
> - handle console_rx == 0 in console_input_domain
> - use rcu_lock_by_domain instead of get_domain_by_id
> - handle the case where the returned domain is NULL
> - send_global_virq(VIRQ_CONSOLE) only when chars are for Dom0
> - make console_rx unsigned int
> - fix comment
> - code readability improvement
> - fix opt_conswitch[1] == 'x' case
> - move console_input_domain to next patch
>
> Changes in v3:
> - only call vpl011 functions ifdef CONFIG_SBSA_VUART_CONSOLE
> - add blank line and spaces
> - remove xen_rx from print messages
> - rename xen_rx to console_rx
> - keep switch_serial_input() at boot
> - add better comments
> - fix existing comment
> - add warning if no guests console/uart is available
> - add console_input_domain function
>
> Changes in v2:
> - only call vpl011_rx_char if the vpl011 has been initialized
> ---
>   xen/drivers/char/console.c | 79 ++++++++++++++++++++++++++++++++++++++--------
>   1 file changed, 65 insertions(+), 14 deletions(-)
>
> diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> index 3b75f7a..75172e7 100644
> --- a/xen/drivers/char/console.c
> +++ b/xen/drivers/char/console.c
> @@ -31,10 +31,13 @@
>   #include <xen/early_printk.h>
>   #include <xen/warning.h>
>   #include <xen/pv_console.h>
> +#include <asm/setup.h>
>   
>   #ifdef CONFIG_X86
>   #include <xen/consoled.h>
>   #include <asm/guest.h>
> +#else
> +#include <asm/vpl011.h>
>   #endif
>   
>   /* console: comma-separated list of console outputs. */
> @@ -391,31 +394,79 @@ static void dump_console_ring_key(unsigned char key)
>       free_xenheap_pages(buf, order);
>   }
>   
> -/* CTRL-<switch_char> switches input direction between Xen and DOM0. */
> +/*
> + * CTRL-<switch_char> changes input direction, rotating among Xen, Dom0,
> + * and DomUs.
> + */
>   #define switch_code (opt_conswitch[0]-'a'+1)
> -static int __read_mostly xen_rx = 1; /* FALSE => input passed to domain 0. */
> +/*
> + * console_rx=0 => input to xen
> + * console_rx=1 => input to dom0
> + * console_rx=N => input to dom(N-1)
> + */
> +static unsigned int __read_mostly console_rx = 0;
>   
>   static void switch_serial_input(void)
>   {
> -    static char *input_str[2] = { "DOM0", "Xen" };
> -    xen_rx = !xen_rx;
> -    printk("*** Serial input -> %s", input_str[xen_rx]);
> +    if ( console_rx++ == max_init_domid + 1 )
> +        console_rx = 0;
> +
> +    if ( console_rx == 0 )
> +        printk("*** Serial input to Xen");
> +    else
> +        printk("*** Serial input to DOM%d", console_rx - 1);
> +
>       if ( switch_code )
> -        printk(" (type 'CTRL-%c' three times to switch input to %s)",
> -               opt_conswitch[0], input_str[!xen_rx]);
> +        printk(" (type 'CTRL-%c' three times to switch input)",
> +               opt_conswitch[0]);
>       printk("\n");
>   }
>   
>   static void __serial_rx(char c, struct cpu_user_regs *regs)
>   {
> -    if ( xen_rx )
> +    switch ( console_rx )
> +    {
> +    case 0:
>           return handle_keypress(c, regs);
> +    case 1:
> +    {
> +        /*
> +         * Deliver input to the hardware domain buffer, unless it is
> +         * already full.
> +         */
> +        if ( (serial_rx_prod - serial_rx_cons) != SERIAL_RX_SIZE )
> +            serial_rx_ring[SERIAL_RX_MASK(serial_rx_prod++)] = c;
> +
> +        /*
> +         * Always notify the hardware domain: prevents receive path from
> +         * getting stuck.
> +         */
> +        send_global_virq(VIRQ_CONSOLE);
> +        break;
> +    }
+ * console_rx=0 => input to xen
+ * console_rx=1 => input to dom0
+ * console_rx=N => input to dom(N-1)
So, why do you only handle case 0/1?
> +#if 0
Do you need this #if 0?
> +    default:
> +    {
> +        struct domain *d = rcu_lock_domain_by_any_id(console_rx - 1);
> +
> +        /*
> +         * If we have a properly initialized vpl011 console for the
> +         * domain, without a full PV ring to Dom0 (in that case input
> +         * comes from the PV ring), then send the character to it.
> +         */
> +        if ( d != NULL &&
> +             !d->arch.vpl011.backend_in_domain &&
> +             d->arch.vpl011.backend.xen != NULL )
> +            vpl011_rx_char_xen(d, c);
> +        else
> +            printk("Cannot send chars to Dom%d: no UART available\n",
> +                   console_rx - 1);
>   
> -    /* Deliver input to guest buffer, unless it is already full. */
> -    if ( (serial_rx_prod-serial_rx_cons) != SERIAL_RX_SIZE )
> -        serial_rx_ring[SERIAL_RX_MASK(serial_rx_prod++)] = c;
> -    /* Always notify the guest: prevents receive path from getting stuck. */
> -    send_global_virq(VIRQ_CONSOLE);
> +        if ( d != NULL )
> +            rcu_unlock_domain(d);
> +    }
> +#endif
> +    }
>   
>   #ifdef CONFIG_X86
>       if ( pv_shim && pv_console )
> @@ -943,7 +994,7 @@ void __init console_endboot(void)
>        * a useful 'how to switch' message.
>        */
>       if ( opt_conswitch[1] == 'x' )
> -        xen_rx = !xen_rx;
> +        console_rx = max_init_domid + 1;
>   
>       register_keyhandler('w', dump_console_ring_key,
>                           "synchronously dump console ring buffer (dmesg)", 0);

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