Re: [PATCH] xen/consoled: clean up console handling for pv_shim

[Denis Mukhin <dmkhn@xxxxxxxxx>]

On Friday, February 21st, 2025 at 4:26 PM, dmkhn@xxxxxxxxx <dmkhn@xxxxxxxxx> 
wrote:

> 
> 
> There are few places which check pv_shim console under CONFIG_PV_SHIM or
> CONFIG_X86 in xen console driver.
> 
> Instead of #ifdef-ing, use new consoled_is_enabled() in switch_serial_input()
> and _serial_rx() (where pv_shim condition is now detected correctly).
> 
> Signature of consoled_guest{rx,tx} has changed so the errors can be logged
> on the callsites.
> 
> Signed-off-by: Denis Mukhin dmukhin@xxxxxxxx

Sorry, I posted too early, there's missing dependency in this patch.
Posted v2 here:
  https://lore.kernel.org/xen-devel/20250222235748.103599-1-dmkhn@xxxxxxxxx/

> 
> ---
> xen/arch/x86/pv/shim.c | 3 +--
> xen/drivers/char/console.c | 15 ++++++---------
> xen/drivers/char/consoled.c | 17 +++++++++++++----
> xen/include/xen/consoled.h | 32 +++++++++++++++++++++++++++-----
> 4 files changed, 47 insertions(+), 20 deletions(-)
> 
> diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
> index b9c034ccff..cbc2e3fced 100644
> --- a/xen/arch/x86/pv/shim.c
> +++ b/xen/arch/x86/pv/shim.c
> @@ -605,8 +605,7 @@ long pv_shim_event_channel_op(int cmd, 
> XEN_GUEST_HANDLE_PARAM(void) arg)
> 
> if ( pv_console && send.port == pv_console_evtchn() )
> {
> - consoled_guest_rx();
> - rc = 0;
> + rc = consoled_guest_rx();
> }
> else
> rc = xen_hypercall_event_channel_op(EVTCHNOP_send, &send);
> diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> index 992b37962e..c207fd8704 100644
> --- a/xen/drivers/char/console.c
> +++ b/xen/drivers/char/console.c
> @@ -32,9 +32,9 @@
> #include <xen/pv_console.h>
> 
> #include <asm/setup.h>
> 
> #include <xen/sections.h>
> 
> +#include <xen/consoled.h>
> 
> 
> #ifdef CONFIG_X86
> -#include <xen/consoled.h>
> 
> #include <asm/guest.h>
> 
> #endif
> #ifdef CONFIG_SBSA_VUART_CONSOLE
> @@ -507,11 +507,9 @@ static void switch_serial_input(void)
> break;
> }
> 
> -#ifdef CONFIG_PV_SHIM
> - if ( next_rx == 1 )
> + if ( consoled_is_enabled() && next_rx == 1 )
> domid = get_initial_domain_id();
> else
> -#endif
> domid = next_rx - 1;
> d = rcu_lock_domain_by_id(domid);
> if ( d )
> @@ -562,13 +560,12 @@ static void __serial_rx(char c)
> rc = vpl011_rx_char_xen(d, c);
> #endif
> 
> -#ifdef CONFIG_X86
> - if ( pv_shim && pv_console )
> - consoled_guest_tx(c);
> -#endif
> + if ( consoled_is_enabled() )
> + /* Deliver input to the PV shim console. */
> + rc = consoled_guest_tx(c);
> 
> if ( rc )
> - guest_printk(d, XENLOG_G_WARNING
> + guest_printk(d, XENLOG_WARNING
> "failed to process console input: %d\n", rc);
> 
> console_put_domain(d);
> diff --git a/xen/drivers/char/consoled.c b/xen/drivers/char/consoled.c
> index b415b632ce..8704ec251e 100644
> --- a/xen/drivers/char/consoled.c
> +++ b/xen/drivers/char/consoled.c
> @@ -43,13 +43,13 @@ struct xencons_interface consoled_get_ring_addr(void)
> static char buf[BUF_SZ + 1];
> 
> / Receives characters from a domain's PV console /
> -void consoled_guest_rx(void)
> +int consoled_guest_rx(void)
> {
> size_t idx = 0;
> XENCONS_RING_IDX cons, prod;
> 
> if ( !cons_ring )
> - return;
> + return -ENODEV;
> 
> spin_lock(&rx_lock);
> 
> @@ -91,15 +91,17 @@ void consoled_guest_rx(void)
> 
> out:
> spin_unlock(&rx_lock);
> +
> + return 0;
> }
> 
> / Sends a character into a domain's PV console */
> -void consoled_guest_tx(char c)
> +int consoled_guest_tx(char c)
> {
> XENCONS_RING_IDX cons, prod;
> 
> if ( !cons_ring )
> - return;
> + return -ENODEV;
> 
> cons = ACCESS_ONCE(cons_ring->in_cons);
> 
> prod = cons_ring->in_prod;
> 
> @@ -125,6 +127,13 @@ void consoled_guest_tx(char c)
> notify:
> /* Always notify the guest: prevents receive path from getting stuck. /
> pv_shim_inject_evtchn(pv_console_evtchn());
> +
> + return 0;
> +}
> +
> +bool consoled_is_enabled(void)
> +{
> + return pv_shim && pv_console;
> }
> 
> /
> diff --git a/xen/include/xen/consoled.h b/xen/include/xen/consoled.h
> index bd7ab6329e..52a1358bea 100644
> --- a/xen/include/xen/consoled.h
> +++ b/xen/include/xen/consoled.h
> @@ -1,14 +1,36 @@
> -#ifndef XEN_CONSOLED_H
> -#define XEN_CONSOLED_H
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef XEN__CONSOLED_H
> +#define XEN__CONSOLED_H
> 
> #include <public/io/console.h>
> 
> 
> +#ifdef CONFIG_PV_SHIM
> +
> void consoled_set_ring_addr(struct xencons_interface *ring);
> struct xencons_interface consoled_get_ring_addr(void);
> -void consoled_guest_rx(void);
> -void consoled_guest_tx(char c);
> +int consoled_guest_rx(void);
> +int consoled_guest_tx(char c);
> +bool consoled_is_enabled(void);
> 
> -#endif / XEN_CONSOLED_H /
> +#else
> +
> +static inline int consoled_guest_rx(void)
> +{
> + ASSERT_UNREACHABLE();
> + return -ENODEV;
> +}
> +
> +static inline int consoled_guest_tx(char c)
> +{
> + ASSERT_UNREACHABLE();
> + return -ENODEV;
> +}
> +
> +#define consoled_is_enabled() (false)
> +
> +#endif / CONFIG_PV_SHIM /
> +
> +#endif / XEN__CONSOLED_H /
> /
> * Local variables:
> * mode: C
> --
> 2.34.1