[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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


  • To: dmkhn@xxxxxxxxx
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Thu, 5 Jun 2025 08:15:15 +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: Thu, 05 Jun 2025 06:15:42 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 05.06.2025 02:57, dmkhn@xxxxxxxxx wrote:
> On Wed, Jun 04, 2025 at 12:48:05PM +0200, Jan Beulich wrote:
>> 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.
> 
> I droppped behavior change for I/O debug port on x86 and HYPERVISOR_console_io
> hypercall.
> 
> But my understanding is that all guest debugging facilities, if enabled, 
> should
> not be rate-limited.

I certainly disagree there. How much rate limiting to apply to guest output is a
matter of the guest_loglvl= command line option. Its default settings are the 
way
they are for a reason.

Jan



 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.