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Re: [PATCH v1 2/2] xen/console: unify printout behavior for UART emulators


  • To: dmkhn@xxxxxxxxx
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Wed, 4 Jun 2025 12:48:05 +0200
  • Autocrypt: addr=jbeulich@xxxxxxxx; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL
  • Cc: andrew.cooper3@xxxxxxxxxx, anthony.perard@xxxxxxxxxx, julien@xxxxxxx, michal.orzel@xxxxxxx, roger.pau@xxxxxxxxxx, sstabellini@xxxxxxxxxx, dmukhin@xxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Wed, 04 Jun 2025 10:48:13 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 31.05.2025 02:04, dmkhn@xxxxxxxxx wrote:
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -577,7 +577,7 @@ static int cf_check hvm_print_line(
>      if ( (cd->pbuf_idx == (DOMAIN_PBUF_SIZE - 1)) || (c == '\n') )
>      {
>          cd->pbuf[cd->pbuf_idx] = '\0';
> -        guest_printk(cd, XENLOG_G_DEBUG "%s\n", cd->pbuf);
> +        guest_printk(cd, "%s\n", cd->pbuf);
>          cd->pbuf_idx = 0;
>      }

Why this and ...

> @@ -755,7 +765,7 @@ static long 
> guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer,
>              else
>              {
>                  cd->pbuf[cd->pbuf_idx] = '\0';
> -                guest_printk(cd, XENLOG_G_DEBUG "%s%s\n", cd->pbuf, kbuf);
> +                guest_printk(cd, "%s%s\n", cd->pbuf, kbuf);
>                  cd->pbuf_idx = 0;
>              }

... this change? There's no compensation for it ...

> @@ -1013,12 +1023,21 @@ void printk(const char *fmt, ...)
>      va_end(args);
>  }
>  
> +/*
> + * Print message from the guest on the diagnostic console.
> + * Prefixes all messages w/ "(dX)" if domain X does not own physical console
> + * focus.
> + */
>  void guest_printk(const struct domain *d, const char *fmt, ...)
>  {
>      va_list args;
> -    char prefix[16];
> +    char prefix[16] = "";
> +    struct domain *consd;
>  
> -    snprintf(prefix, sizeof(prefix), "(d%d) ", d->domain_id);
> +    consd = console_get_domain();
> +    if ( consd != d )
> +        snprintf(prefix, sizeof(prefix), "(d%d) ", d->domain_id);
> +    console_put_domain(consd);
>  
>      va_start(args, fmt);
>      vprintk_common(fmt, args, prefix);

... here afaics, so it looks like you're undermining rate-limiting of
those messages.

Jan



 


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