| Message ID | 20241205-vuart-ns8250-v1-23-e9aa923127eb@ford.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Introduce NS8250 UART emulator | expand |
On Thu, Dec 05, 2024 at 08:41:53PM -0800, Denis Mukhin via B4 Relay wrote: > From: Denis Mukhin <dmukhin@ford.com> > > PV Linux kernel uses HYPERVISOR_console_io hypercall for early console which > ends up being handled by Xen's console driver's guest_console_write(). > > guest_console_write() duplicates the code from __putstr(), elimitate code > duplication. It might be better to split the code that unifies guest_console_write() and __putstr() as a non-functional change. While the introduction of use_conring is likely a functional change. > Signed-off-by: Denis Mukhin <dmukhin@ford.com> > --- > xen/drivers/char/console.c | 97 +++++++++++++++++++++++++--------------------- > 1 file changed, 53 insertions(+), 44 deletions(-) > > diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c > index ce3639a4cdcda00ea63e3bf119bc3b242cbfdf6a..115967d179998cba4a81578caba09db4e4aca7f7 100644 > --- a/xen/drivers/char/console.c > +++ b/xen/drivers/char/console.c > @@ -63,6 +63,8 @@ static const char __initconst warning_sync_console[] = > "However it can introduce SIGNIFICANT latencies and affect\n" > "timekeeping. It is NOT recommended for production use!\n"; > > +/* Flag: use conring for early console; switches to opt_console_to_ring */ > +static bool __read_mostly use_conring = true; __ro_after_init instead of __read_mostly. > /* console_to_ring: send guest (incl. dom 0) console data to console ring. */ > static bool __read_mostly opt_console_to_ring; > boolean_param("console_to_ring", opt_console_to_ring); > @@ -661,6 +663,16 @@ static void cf_check notify_dom0_con_ring(void *unused) > static DECLARE_SOFTIRQ_TASKLET(notify_dom0_con_ring_tasklet, > notify_dom0_con_ring, NULL); > > +static bool console_locks_busted; > + > +static void conring_write(const char *str, size_t len) > +{ > + conring_puts(str, len); > + > + if ( !console_locks_busted ) > + tasklet_schedule(¬ify_dom0_con_ring_tasklet); > +} > + > #ifdef CONFIG_X86 > static inline void xen_console_write_debug_port(const char *buf, size_t len) > { > @@ -669,8 +681,44 @@ static inline void xen_console_write_debug_port(const char *buf, size_t len) > : "=&S" (tmp), "=&c" (tmp) > : "0" (buf), "1" (len), "d" (XEN_HVM_DEBUGCONS_IOPORT) ); > } > + > +static void xen_console_write(const char *str, size_t len) > +{ > + if ( xen_guest ) > + xen_hypercall_console_write(str, len); > + else > + xen_console_write_debug_port(str, len); > +} > +#else > +static inline void xen_console_write(const char *str, size_t len) > +{ opt_console_xen would only be set on x86 with the current command line parsing done in console_init_preirq(), so you could add an ASSERT_UNREACHABLE() here. > +} > #endif > > +/* > + * Write characters to console. > + * > + * That will handle all possible scenarios working w/ console > + * - serial console; > + * - video output; > + * - __HYPERVISOR_console_io hypercall (x86 only); > + * - debug I/O port (x86 only); > + * - forward to Xen event channel. "Xen event channel" is not the correct term. I would use "PV console". The event channel is just used to send the notification. > + */ > +static void console_write(const char *str, size_t len) > +{ > + ASSERT(rspin_is_locked(&console_lock)); > + > + console_serial_puts(str, len); > + video_puts(str, len); > + > + if ( opt_console_xen ) > + xen_console_write(str, len); Are you sure this builds? opt_console_xen is only defined on x86, and AFAICT console_write() is generic. AFAICT you need to keep the X86 preprocessor guards, or alternatively do something like: #define opt_console_xen false For non-x86 arches in xen/console.h > + > + if ( use_conring ) > + conring_write(str, len); > +} > + > static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, > unsigned int count) > { > @@ -691,28 +739,8 @@ static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, > > if ( is_hardware_domain(cd) ) > { > - /* Use direct console output as it could be interactive */ > nrspin_lock_irq(&console_lock); > - > - console_serial_puts(kbuf, kcount); > - video_puts(kbuf, kcount); > - > -#ifdef CONFIG_X86 > - if ( opt_console_xen ) > - { > - if ( xen_guest ) > - xen_hypercall_console_write(kbuf, kcount); > - else > - xen_console_write_debug_port(kbuf, kcount); > - } > -#endif > - > - if ( opt_console_to_ring ) > - { > - conring_puts(kbuf, kcount); > - tasklet_schedule(¬ify_dom0_con_ring_tasklet); > - } > - > + console_write(kbuf, kcount); > nrspin_unlock_irq(&console_lock); > } > else > @@ -813,31 +841,9 @@ long do_console_io( > * ***************************************************** > */ > > -static bool console_locks_busted; > - > static void __putstr(const char *str) > { > - size_t len = strlen(str); > - > - ASSERT(rspin_is_locked(&console_lock)); > - > - console_serial_puts(str, len); > - video_puts(str, len); > - > -#ifdef CONFIG_X86 > - if ( opt_console_xen ) > - { > - if ( xen_guest ) > - xen_hypercall_console_write(str, len); > - else > - xen_console_write_debug_port(str, len); > - } > -#endif > - > - conring_puts(str, len); > - > - if ( !console_locks_busted ) > - tasklet_schedule(¬ify_dom0_con_ring_tasklet); > + console_write(str, strlen(str)); > } > > static int printk_prefix_check(char *p, char **pp) > @@ -1171,6 +1177,9 @@ void __init console_endboot(void) > > video_endboot(); > > + use_conring = opt_console_to_ring; > + smp_wmb(); Do you really need the barrier? If so it would need a comment describing exactly why it's needed. I don't think it's possible for the write to be reordered past the return of the function, which would be enough to ensure correctness? Thanks, Roger.
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c index ce3639a4cdcda00ea63e3bf119bc3b242cbfdf6a..115967d179998cba4a81578caba09db4e4aca7f7 100644 --- a/xen/drivers/char/console.c +++ b/xen/drivers/char/console.c @@ -63,6 +63,8 @@ static const char __initconst warning_sync_console[] = "However it can introduce SIGNIFICANT latencies and affect\n" "timekeeping. It is NOT recommended for production use!\n"; +/* Flag: use conring for early console; switches to opt_console_to_ring */ +static bool __read_mostly use_conring = true; /* console_to_ring: send guest (incl. dom 0) console data to console ring. */ static bool __read_mostly opt_console_to_ring; boolean_param("console_to_ring", opt_console_to_ring); @@ -661,6 +663,16 @@ static void cf_check notify_dom0_con_ring(void *unused) static DECLARE_SOFTIRQ_TASKLET(notify_dom0_con_ring_tasklet, notify_dom0_con_ring, NULL); +static bool console_locks_busted; + +static void conring_write(const char *str, size_t len) +{ + conring_puts(str, len); + + if ( !console_locks_busted ) + tasklet_schedule(¬ify_dom0_con_ring_tasklet); +} + #ifdef CONFIG_X86 static inline void xen_console_write_debug_port(const char *buf, size_t len) { @@ -669,8 +681,44 @@ static inline void xen_console_write_debug_port(const char *buf, size_t len) : "=&S" (tmp), "=&c" (tmp) : "0" (buf), "1" (len), "d" (XEN_HVM_DEBUGCONS_IOPORT) ); } + +static void xen_console_write(const char *str, size_t len) +{ + if ( xen_guest ) + xen_hypercall_console_write(str, len); + else + xen_console_write_debug_port(str, len); +} +#else +static inline void xen_console_write(const char *str, size_t len) +{ +} #endif +/* + * Write characters to console. + * + * That will handle all possible scenarios working w/ console + * - serial console; + * - video output; + * - __HYPERVISOR_console_io hypercall (x86 only); + * - debug I/O port (x86 only); + * - forward to Xen event channel. + */ +static void console_write(const char *str, size_t len) +{ + ASSERT(rspin_is_locked(&console_lock)); + + console_serial_puts(str, len); + video_puts(str, len); + + if ( opt_console_xen ) + xen_console_write(str, len); + + if ( use_conring ) + conring_write(str, len); +} + static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, unsigned int count) { @@ -691,28 +739,8 @@ static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, if ( is_hardware_domain(cd) ) { - /* Use direct console output as it could be interactive */ nrspin_lock_irq(&console_lock); - - console_serial_puts(kbuf, kcount); - video_puts(kbuf, kcount); - -#ifdef CONFIG_X86 - if ( opt_console_xen ) - { - if ( xen_guest ) - xen_hypercall_console_write(kbuf, kcount); - else - xen_console_write_debug_port(kbuf, kcount); - } -#endif - - if ( opt_console_to_ring ) - { - conring_puts(kbuf, kcount); - tasklet_schedule(¬ify_dom0_con_ring_tasklet); - } - + console_write(kbuf, kcount); nrspin_unlock_irq(&console_lock); } else @@ -813,31 +841,9 @@ long do_console_io( * ***************************************************** */ -static bool console_locks_busted; - static void __putstr(const char *str) { - size_t len = strlen(str); - - ASSERT(rspin_is_locked(&console_lock)); - - console_serial_puts(str, len); - video_puts(str, len); - -#ifdef CONFIG_X86 - if ( opt_console_xen ) - { - if ( xen_guest ) - xen_hypercall_console_write(str, len); - else - xen_console_write_debug_port(str, len); - } -#endif - - conring_puts(str, len); - - if ( !console_locks_busted ) - tasklet_schedule(¬ify_dom0_con_ring_tasklet); + console_write(str, strlen(str)); } static int printk_prefix_check(char *p, char **pp) @@ -1171,6 +1177,9 @@ void __init console_endboot(void) video_endboot(); + use_conring = opt_console_to_ring; + smp_wmb(); + register_keyhandler('w', dump_console_ring_key, "synchronously dump console ring buffer (dmesg)", 0); register_irq_keyhandler('+', &do_inc_thresh,