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Re: [Xen-devel] [PATCH v2] xen/console: buffer and show origin of guest PV writes



On 16/08/2013 20:01, "Daniel De Graaf" <dgdegra@xxxxxxxxxxxxx> wrote:

> Guests other than domain 0 using the console output have previously been
> controlled by the VERBOSE define, but with no designation of which
> guest's output was on the console. This patch converts the HVM output
> buffering to be used by all domains, line buffering their output and
> prefixing it with the domain ID. This is especially useful for debugging
> stub domains.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>

This seems good, but, if we process and buffer dom0's output, we lose the
possibility of running a terminal session in dom0 over the Xen console.
Personally I do that quite a bit -- serial access only, get Xen's debugging
there, but also can log in to dom0. Does noone else??

 -- Keir

> ---
> 
> Changes since v1 (RFC):
>  - Use prefix of (d%d) in place of (XEN) for both PV and HVM output
>  - Guests other than dom0 have non-printable characters stripped
>  - Use unsigned type for pbuf_idx
>  - Formatting fixes
> 
>  xen/arch/x86/hvm/hvm.c           | 27 +++++-------
>  xen/common/domain.c              |  8 ++++
>  xen/drivers/char/console.c       | 94
> ++++++++++++++++++++++++++++++++--------
>  xen/include/asm-x86/hvm/domain.h |  6 ---
>  xen/include/xen/lib.h            |  2 +
>  xen/include/xen/sched.h          |  6 +++
>  6 files changed, 103 insertions(+), 40 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 1fcaed0..4ff76cc 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -485,8 +485,7 @@ static int hvm_set_ioreq_page(
>  static int hvm_print_line(
>      int dir, uint32_t port, uint32_t bytes, uint32_t *val)
>  {
> -    struct vcpu *curr = current;
> -    struct hvm_domain *hd = &curr->domain->arch.hvm_domain;
> +    struct domain *cd = current->domain;
>      char c = *val;
>  
>      BUG_ON(bytes != 1);
> @@ -495,17 +494,16 @@ static int hvm_print_line(
>      if ( !isprint(c) && (c != '\n') && (c != '\t') )
>          return X86EMUL_OKAY;
>  
> -    spin_lock(&hd->pbuf_lock);
> -    hd->pbuf[hd->pbuf_idx++] = c;
> -    if ( (hd->pbuf_idx == (HVM_PBUF_SIZE - 2)) || (c == '\n') )
> +    spin_lock(&cd->pbuf_lock);
> +    if ( c != '\n' )
> +        cd->pbuf[cd->pbuf_idx++] = c;
> +    if ( (cd->pbuf_idx == (DOMAIN_PBUF_SIZE - 1)) || (c == '\n') )
>      {
> -        if ( c != '\n' )
> -            hd->pbuf[hd->pbuf_idx++] = '\n';
> -        hd->pbuf[hd->pbuf_idx] = '\0';
> -        printk(XENLOG_G_DEBUG "HVM%u: %s", curr->domain->domain_id,
> hd->pbuf);
> -        hd->pbuf_idx = 0;
> +        cd->pbuf[cd->pbuf_idx] = '\0';
> +        guest_printk(cd, XENLOG_G_DEBUG "%s\n", cd->pbuf);
> +        cd->pbuf_idx = 0;
>      }
> -    spin_unlock(&hd->pbuf_lock);
> +    spin_unlock(&cd->pbuf_lock);
>  
>      return X86EMUL_OKAY;
>  }
> @@ -521,19 +519,16 @@ int hvm_domain_initialise(struct domain *d)
>          return -EINVAL;
>      }
>  
> -    spin_lock_init(&d->arch.hvm_domain.pbuf_lock);
>      spin_lock_init(&d->arch.hvm_domain.irq_lock);
>      spin_lock_init(&d->arch.hvm_domain.uc_lock);
>  
>      INIT_LIST_HEAD(&d->arch.hvm_domain.msixtbl_list);
>      spin_lock_init(&d->arch.hvm_domain.msixtbl_list_lock);
>  
> -    d->arch.hvm_domain.pbuf = xzalloc_array(char, HVM_PBUF_SIZE);
>      d->arch.hvm_domain.params = xzalloc_array(uint64_t, HVM_NR_PARAMS);
>      d->arch.hvm_domain.io_handler = xmalloc(struct hvm_io_handler);
>      rc = -ENOMEM;
> -    if ( !d->arch.hvm_domain.pbuf || !d->arch.hvm_domain.params ||
> -         !d->arch.hvm_domain.io_handler )
> +    if ( !d->arch.hvm_domain.params || !d->arch.hvm_domain.io_handler )
>          goto fail0;
>      d->arch.hvm_domain.io_handler->num_slot = 0;
>  
> @@ -578,7 +573,6 @@ int hvm_domain_initialise(struct domain *d)
>   fail0:
>      xfree(d->arch.hvm_domain.io_handler);
>      xfree(d->arch.hvm_domain.params);
> -    xfree(d->arch.hvm_domain.pbuf);
>      return rc;
>  }
>  
> @@ -603,7 +597,6 @@ void hvm_domain_relinquish_resources(struct domain *d)
>  
>      xfree(d->arch.hvm_domain.io_handler);
>      xfree(d->arch.hvm_domain.params);
> -    xfree(d->arch.hvm_domain.pbuf);
>  }
>  
>  void hvm_domain_destroy(struct domain *d)
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index 6c264a5..daac2c9 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -231,6 +231,8 @@ struct domain *domain_create(
>      spin_lock_init(&d->shutdown_lock);
>      d->shutdown_code = -1;
>  
> +    spin_lock_init(&d->pbuf_lock);
> +
>      err = -ENOMEM;
>      if ( !zalloc_cpumask_var(&d->domain_dirty_cpumask) )
>          goto fail;
> @@ -286,6 +288,10 @@ struct domain *domain_create(
>          d->mem_event = xzalloc(struct mem_event_per_domain);
>          if ( !d->mem_event )
>              goto fail;
> +
> +        d->pbuf = xzalloc_array(char, DOMAIN_PBUF_SIZE);
> +        if ( !d->pbuf )
> +            goto fail;
>      }
>  
>      if ( (err = arch_domain_create(d, domcr_flags)) != 0 )
> @@ -318,6 +324,7 @@ struct domain *domain_create(
>      d->is_dying = DOMDYING_dead;
>      atomic_set(&d->refcnt, DOMAIN_DESTROYED);
>      xfree(d->mem_event);
> +    xfree(d->pbuf);
>      if ( init_status & INIT_arch )
>          arch_domain_destroy(d);
>      if ( init_status & INIT_gnttab )
> @@ -730,6 +737,7 @@ static void complete_domain_destroy(struct rcu_head *head)
>  #endif
>  
>      xfree(d->mem_event);
> +    xfree(d->pbuf);
>  
>      for ( i = d->max_vcpus - 1; i >= 0; i-- )
>          if ( (v = d->vcpu[i]) != NULL )
> diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> index 8ac32e4..b8d9a9f 100644
> --- a/xen/drivers/char/console.c
> +++ b/xen/drivers/char/console.c
> @@ -24,6 +24,7 @@
>  #include <xen/shutdown.h>
>  #include <xen/video.h>
>  #include <xen/kexec.h>
> +#include <xen/ctype.h>
>  #include <asm/debugger.h>
>  #include <asm/div64.h>
>  #include <xen/hypercall.h> /* for do_console_io */
> @@ -375,6 +376,7 @@ static long
> guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, int count)
>  {
>      char kbuf[128];
>      int kcount;
> +    struct domain *cd = current->domain;
>  
>      while ( count > 0 )
>      {
> @@ -388,19 +390,60 @@ static long
> guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, int count)
>              return -EFAULT;
>          kbuf[kcount] = '\0';
>  
> -        spin_lock_irq(&console_lock);
> +        if ( is_hardware_domain(cd) )
> +        {
> +            /* Use direct console output as it could be interactive */
> +            spin_lock_irq(&console_lock);
> +
> +            sercon_puts(kbuf);
> +            video_puts(kbuf);
>  
> -        sercon_puts(kbuf);
> -        video_puts(kbuf);
> +            if ( opt_console_to_ring )
> +            {
> +                conring_puts(kbuf);
> +                tasklet_schedule(&notify_dom0_con_ring_tasklet);
> +            }
>  
> -        if ( opt_console_to_ring )
> +            spin_unlock_irq(&console_lock);
> +        }
> +        else
>          {
> -            conring_puts(kbuf);
> -            tasklet_schedule(&notify_dom0_con_ring_tasklet);
> +            char *kin = kbuf;
> +            char *kout = kbuf;
> +            char c;
> +            /* Strip non-printable characters */
> +            for ( ; ; )
> +            {
> +                c = *kin++;
> +                if ( c == '\0' || c == '\n' )
> +                    break;
> +                if ( isprint(c) || c == '\t' )
> +                    *kout++ = c;
> +            }
> +            *kout = '\0';
> +            spin_lock(&cd->pbuf_lock);
> +            if ( c == '\n' )
> +            {
> +                kcount = kin - kbuf;
> +                cd->pbuf[cd->pbuf_idx] = '\0';
> +                guest_printk(cd, XENLOG_G_DEBUG "%s%s\n", cd->pbuf, kbuf);
> +                cd->pbuf_idx = 0;
> +            }
> +            else if ( cd->pbuf_idx + kcount < (DOMAIN_PBUF_SIZE - 1) )
> +            {
> +                /* buffer the output until a newline */
> +                memcpy(cd->pbuf + cd->pbuf_idx, kbuf, kcount);
> +                cd->pbuf_idx += kcount;
> +            }
> +            else
> +            {
> +                cd->pbuf[cd->pbuf_idx] = '\0';
> +                guest_printk(cd, XENLOG_G_DEBUG "%s%s\n", cd->pbuf, kbuf);
> +                cd->pbuf_idx = 0;
> +            }
> +            spin_unlock(&cd->pbuf_lock);
>          }
>  
> -        spin_unlock_irq(&console_lock);
> -
>          guest_handle_add_offset(buffer, kcount);
>          count -= kcount;
>      }
> @@ -504,12 +547,12 @@ static int printk_prefix_check(char *p, char **pp)
>              ((loglvl < upper_thresh) && printk_ratelimit()));
>  } 
>  
> -static void printk_start_of_line(void)
> +static void printk_start_of_line(const char *prefix)
>  {
>      struct tm tm;
>      char tstr[32];
>  
> -    __putstr("(XEN) ");
> +    __putstr(prefix);
>  
>      if ( !opt_console_timestamps )
>          return;
> @@ -524,12 +567,11 @@ static void printk_start_of_line(void)
>      __putstr(tstr);
>  }
>  
> -void printk(const char *fmt, ...)
> +static void vprintk_common(const char *prefix, const char *fmt, va_list args)
>  {
>      static char   buf[1024];
>      static int    start_of_line = 1, do_print;
>  
> -    va_list       args;
>      char         *p, *q;
>      unsigned long flags;
>  
> @@ -537,9 +579,7 @@ void printk(const char *fmt, ...)
>      local_irq_save(flags);
>      spin_lock_recursive(&console_lock);
>  
> -    va_start(args, fmt);
>      (void)vsnprintf(buf, sizeof(buf), fmt, args);
> -    va_end(args);
>  
>      p = buf;
>  
> @@ -551,7 +591,7 @@ void printk(const char *fmt, ...)
>          if ( do_print )
>          {
>              if ( start_of_line )
> -                printk_start_of_line();
> +                printk_start_of_line(prefix);
>              __putstr(p);
>              __putstr("\n");
>          }
> @@ -566,7 +606,7 @@ void printk(const char *fmt, ...)
>          if ( do_print )
>          {
>              if ( start_of_line )
> -                printk_start_of_line();
> +                printk_start_of_line(prefix);
>              __putstr(p);
>          }
>          start_of_line = 0;
> @@ -576,6 +616,26 @@ void printk(const char *fmt, ...)
>      local_irq_restore(flags);
>  }
>  
> +void printk(const char *fmt, ...)
> +{
> +    va_list args;
> +    va_start(args, fmt);
> +    vprintk_common("(XEN) ", fmt, args);
> +    va_end(args);
> +}
> +
> +void guest_printk(struct domain *d, const char *fmt, ...)
> +{
> +    va_list args;
> +    char prefix[16];
> +
> +    snprintf(prefix, sizeof(prefix), "(d%d) ", d->domain_id);
> +
> +    va_start(args, fmt);
> +    vprintk_common(prefix, fmt, args);
> +    va_end(args);
> +}
> +
>  void __init console_init_preirq(void)
>  {
>      char *p;
> @@ -791,7 +851,7 @@ int __printk_ratelimit(int ratelimit_ms, int
> ratelimit_burst)
>              snprintf(lost_str, sizeof(lost_str), "%d", lost);
>              /* console_lock may already be acquired by printk(). */
>              spin_lock_recursive(&console_lock);
> -            printk_start_of_line();
> +            printk_start_of_line("(XEN) ");
>              __putstr("printk: ");
>              __putstr(lost_str);
>              __putstr(" messages suppressed.\n");
> diff --git a/xen/include/asm-x86/hvm/domain.h
> b/xen/include/asm-x86/hvm/domain.h
> index 27b3de5..b1e3187 100644
> --- a/xen/include/asm-x86/hvm/domain.h
> +++ b/xen/include/asm-x86/hvm/domain.h
> @@ -62,12 +62,6 @@ struct hvm_domain {
>      /* emulated irq to pirq */
>      struct radix_tree_root emuirq_pirq;
>  
> -    /* hvm_print_line() logging. */
> -#define HVM_PBUF_SIZE 80
> -    char                  *pbuf;
> -    int                    pbuf_idx;
> -    spinlock_t             pbuf_lock;
> -
>      uint64_t              *params;
>  
>      /* Memory ranges with pinned cache attributes. */
> diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
> index 74b34eb..40afe12 100644
> --- a/xen/include/xen/lib.h
> +++ b/xen/include/xen/lib.h
> @@ -83,6 +83,8 @@ extern void debugtrace_printk(const char *fmt, ...);
>  #define _p(_x) ((void *)(unsigned long)(_x))
>  extern void printk(const char *format, ...)
>      __attribute__ ((format (printf, 1, 2)));
> +extern void guest_printk(struct domain *d, const char *format, ...)
> +    __attribute__ ((format (printf, 2, 3)));
>  extern void panic(const char *format, ...)
>      __attribute__ ((format (printf, 1, 2)));
>  extern long vm_assist(struct domain *, unsigned int, unsigned int);
> diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
> index ae6a3b8..0013a8d 100644
> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -341,6 +341,12 @@ struct domain
>      /* Control-plane tools handle for this domain. */
>      xen_domain_handle_t handle;
>  
> +    /* hvm_print_line() and guest_console_write() logging. */
> +#define DOMAIN_PBUF_SIZE 80
> +    char       *pbuf;
> +    unsigned    pbuf_idx;
> +    spinlock_t  pbuf_lock;
> +
>      /* OProfile support. */
>      struct xenoprof *xenoprof;
>      int32_t time_offset_seconds;



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