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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v4 3/4] xen/console: remove max_init_domid dependency
On Thu, 29 May 2025, dmkhn@xxxxxxxxx wrote:
> From: Denis Mukhin <dmkhn@xxxxxxxxx>
>
> From: Denis Mukhin <dmukhin@xxxxxxxx>
>
> The physical console input rotation depends on max_init_domid symbol, which is
> managed differently across architectures.
>
> Instead of trying to manage max_init_domid in the arch-common code the console
> input rotation code can be reworked by removing dependency on max_init_domid
> entirely.
>
> To do that, introduce domid_find_with_input_allowed() in arch-independent
> location to find the ID of the next possible console owner domain. The IDs
> are rotated across non-system domain IDs and DOMID_XEN.
>
> Also, introduce helper console_set_domid() for updating identifier of the
> current console input owner (points to Xen or domain).
>
> Use domid_find_with_input_allowed() and console_set_domid() in
> console_switch_input().
>
> Remove uses of max_init_domid in the code.
>
> Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
> ---
> Changes since v3:
> - switched to RCU lock in domid_find_with_input_allowed()
> ---
> xen/arch/arm/include/asm/setup.h | 2 -
> xen/arch/arm/setup.c | 2 -
> xen/arch/ppc/include/asm/setup.h | 2 -
> xen/arch/riscv/include/asm/setup.h | 2 -
> xen/arch/x86/include/asm/setup.h | 2 -
> xen/common/device-tree/dom0less-build.c | 2 -
> xen/common/domain.c | 29 ++++++++
> xen/drivers/char/console.c | 90 +++++++++----------------
> xen/include/xen/domain.h | 1 +
> 9 files changed, 61 insertions(+), 71 deletions(-)
>
> diff --git a/xen/arch/arm/include/asm/setup.h
> b/xen/arch/arm/include/asm/setup.h
> index 6cf272c160..f107e8eebb 100644
> --- a/xen/arch/arm/include/asm/setup.h
> +++ b/xen/arch/arm/include/asm/setup.h
> @@ -25,8 +25,6 @@ struct map_range_data
> struct rangeset *irq_ranges;
> };
>
> -extern domid_t max_init_domid;
> -
> void copy_from_paddr(void *dst, paddr_t paddr, unsigned long len);
>
> size_t estimate_efi_size(unsigned int mem_nr_banks);
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 10b46d0684..53e2f8b537 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -61,8 +61,6 @@ struct cpuinfo_arm __read_mostly system_cpuinfo;
> bool __read_mostly acpi_disabled;
> #endif
>
> -domid_t __read_mostly max_init_domid;
> -
> static __used void init_done(void)
> {
> int rc;
> diff --git a/xen/arch/ppc/include/asm/setup.h
> b/xen/arch/ppc/include/asm/setup.h
> index e4f64879b6..956fa6985a 100644
> --- a/xen/arch/ppc/include/asm/setup.h
> +++ b/xen/arch/ppc/include/asm/setup.h
> @@ -1,6 +1,4 @@
> #ifndef __ASM_PPC_SETUP_H__
> #define __ASM_PPC_SETUP_H__
>
> -#define max_init_domid (0)
> -
> #endif /* __ASM_PPC_SETUP_H__ */
> diff --git a/xen/arch/riscv/include/asm/setup.h
> b/xen/arch/riscv/include/asm/setup.h
> index c9d69cdf51..d1fc64b673 100644
> --- a/xen/arch/riscv/include/asm/setup.h
> +++ b/xen/arch/riscv/include/asm/setup.h
> @@ -5,8 +5,6 @@
>
> #include <xen/types.h>
>
> -#define max_init_domid (0)
> -
> void setup_mm(void);
>
> void copy_from_paddr(void *dst, paddr_t paddr, unsigned long len);
> diff --git a/xen/arch/x86/include/asm/setup.h
> b/xen/arch/x86/include/asm/setup.h
> index ac34c69855..b67de8577f 100644
> --- a/xen/arch/x86/include/asm/setup.h
> +++ b/xen/arch/x86/include/asm/setup.h
> @@ -69,6 +69,4 @@ extern bool opt_dom0_verbose;
> extern bool opt_dom0_cpuid_faulting;
> extern bool opt_dom0_msr_relaxed;
>
> -#define max_init_domid (0)
> -
> #endif
> diff --git a/xen/common/device-tree/dom0less-build.c
> b/xen/common/device-tree/dom0less-build.c
> index 9a6015f4ce..703f20faed 100644
> --- a/xen/common/device-tree/dom0less-build.c
> +++ b/xen/common/device-tree/dom0less-build.c
> @@ -977,8 +977,6 @@ void __init create_domUs(void)
> domid = domid_alloc(DOMID_INVALID);
> if ( domid == DOMID_INVALID )
> panic("Error allocating ID for domain %s\n", dt_node_name(node));
> - if ( max_init_domid < domid )
> - max_init_domid = domid;
>
> d = domain_create(domid, &d_cfg, flags);
> if ( IS_ERR(d) )
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index 9bc66d80c4..704e0907e9 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -2463,6 +2463,35 @@ void domid_free(domid_t domid)
> spin_unlock(&domid_lock);
> }
>
> +/*
> + * Find the ID of the next possible console owner domain.
> + *
> + * @return Domain ID: DOMID_XEN or non-system domain IDs within
> + * the range of [0..DOMID_FIRST_RESERVED-1].
> + */
> +domid_t domid_find_with_input_allowed(domid_t hint)
> +{
> + const struct domain *d;
> + domid_t domid = DOMID_XEN;
> +
> + rcu_read_lock(&domlist_read_lock);
> +
> + for ( d = rcu_dereference(domain_list);
> + d && d->domain_id < DOMID_FIRST_RESERVED;
> + d = rcu_dereference(d->next_in_list) )
> + {
> + if ( d->console.input_allowed )
> + {
> + domid = d->domain_id;
> + break;
> + }
> + }
> +
> + rcu_read_unlock(&domlist_read_lock);
Doesn't this always return the first domid with input_allowed given that
hint is not used? It looks like it wouldn't work right...
> + return domid;
> +}
> +
> /*
> * Local variables:
> * mode: C
> diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> index 8a0bcff78f..37289d5558 100644
> --- a/xen/drivers/char/console.c
> +++ b/xen/drivers/char/console.c
> @@ -498,26 +498,17 @@ static void cf_check conring_dump_keyhandler(unsigned
> char key)
>
> /*
> * CTRL-<switch_char> changes input direction, rotating among Xen, Dom0,
> - * and the DomUs started from Xen at boot.
> + * and the DomUs.
> */
> #define switch_code (opt_conswitch[0]-'a'+1)
> -/*
> - * console_rx=0 => input to xen
> - * console_rx=1 => input to dom0 (or the sole shim domain)
> - * console_rx=N => input to dom(N-1)
> - */
> -static unsigned int __read_mostly console_rx = 0;
>
> -#define max_console_rx (max_init_domid + 1)
> +/* Console owner domain identifier. */
> +static domid_t __read_mostly console_rx = DOMID_XEN;
>
> struct domain *console_get_domain(void)
> {
> - struct domain *d;
> + struct domain *d = rcu_lock_domain_by_id(console_rx);
>
> - if ( console_rx == 0 )
> - return NULL;
> -
> - d = rcu_lock_domain_by_id(console_rx - 1);
> if ( !d )
> return NULL;
>
> @@ -535,43 +526,14 @@ void console_put_domain(struct domain *d)
> rcu_unlock_domain(d);
> }
>
> -static void console_switch_input(void)
> +static void console_set_domid(domid_t domid)
> {
> - unsigned int next_rx = console_rx;
> + if ( domid == DOMID_XEN )
> + printk("*** Serial input to Xen");
> + else
> + printk("*** Serial input to DOM%u", domid);
>
> - /*
> - * Rotate among Xen, dom0 and boot-time created domUs while skipping
> - * switching serial input to non existing domains.
> - */
> - for ( ; ; )
> - {
> - domid_t domid;
> - struct domain *d;
> -
> - if ( next_rx++ >= max_console_rx )
> - {
> - console_rx = 0;
> - printk("*** Serial input to Xen");
> - break;
> - }
> -
> - if ( consoled_is_enabled() && next_rx == 1 )
> - domid = get_initial_domain_id();
> - else
> - domid = next_rx - 1;
> - d = rcu_lock_domain_by_id(domid);
> - if ( d )
> - {
> - rcu_unlock_domain(d);
> -
> - if ( !d->console.input_allowed )
> - break;
> -
> - console_rx = next_rx;
> - printk("*** Serial input to DOM%u", domid);
> - break;
> - }
> - }
> + console_rx = domid;
>
> if ( switch_code )
> printk(" (type 'CTRL-%c' three times to switch input)",
> @@ -579,12 +541,30 @@ static void console_switch_input(void)
> printk("\n");
> }
>
> +/*
> + * Switch console focus.
> + * Rotates input focus among Xen and domains with console input permission.
> + */
> +static void console_switch_input(void)
> +{
> + domid_t hint;
> +
> + if ( console_rx == DOMID_XEN )
> + hint = get_initial_domain_id();
> + else
> + hint = console_rx + 1;
> +
> + hint = domid_find_with_input_allowed(hint);
> +
> + console_set_domid(hint);
> +}
> +
> static void __serial_rx(char c)
> {
> struct domain *d;
> int rc = 0;
>
> - if ( console_rx == 0 )
> + if ( console_rx == DOMID_XEN )
> return handle_keypress(c, false);
>
> d = console_get_domain();
> @@ -1169,14 +1149,6 @@ void __init console_endboot(void)
>
> video_endboot();
>
> - /*
> - * If user specifies so, we fool the switch routine to redirect input
> - * straight back to Xen. I use this convoluted method so we still print
> - * a useful 'how to switch' message.
> - */
> - if ( opt_conswitch[1] == 'x' )
> - console_rx = max_console_rx;
> -
> register_keyhandler('w', conring_dump_keyhandler,
> "synchronously dump console ring buffer (dmesg)", 0);
> register_irq_keyhandler('+', &do_inc_thresh,
> @@ -1186,8 +1158,8 @@ void __init console_endboot(void)
> register_irq_keyhandler('G', &do_toggle_guest,
> "toggle host/guest log level adjustment", 0);
>
> - /* Serial input is directed to DOM0 by default. */
> - console_switch_input();
> + if ( opt_conswitch[1] != 'x' )
> + (void)console_set_domid(get_initial_domain_id());
We should use domid_find_with_input_allowed instead of assuming
get_initial_domain_id() has input_allowed?
> }
>
> int __init console_has(const char *device)
> diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
> index 8aab05ae93..a88eb34f3f 100644
> --- a/xen/include/xen/domain.h
> +++ b/xen/include/xen/domain.h
> @@ -36,6 +36,7 @@ void getdomaininfo(struct domain *d, struct
> xen_domctl_getdomaininfo *info);
> void arch_get_domain_info(const struct domain *d,
> struct xen_domctl_getdomaininfo *info);
>
> +domid_t domid_find_with_input_allowed(domid_t hint);
> domid_t get_initial_domain_id(void);
>
> domid_t domid_alloc(domid_t domid);
> --
> 2.34.1
>
>
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