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Tue, 10 Feb 2026 07:10:43 -0800 (PST) Message-ID: <75df20e0-70f0-454c-9797-e62725f53b63@suse.com> Date: Tue, 10 Feb 2026 16:10:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 6/6] xen/console: add conring buffer size alignment setting To: dmukhin@xen.org Cc: andrew.cooper3@citrix.com, anthony.perard@vates.tech, julien@xen.org, michal.orzel@amd.com, roger.pau@citrix.com, sstabellini@kernel.org, dmukhin@ford.com, xen-devel@lists.xenproject.org References: <20260205013606.3384798-1-dmukhin@ford.com> <20260205013606.3384798-7-dmukhin@ford.com> Content-Language: en-US From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; 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 In-Reply-To: <20260205013606.3384798-7-dmukhin@ford.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 05.02.2026 02:36, dmukhin@xen.org wrote: > From: Denis Mukhin > > Introduce CONFIG_CONRING_ALIGN_PAGE_SIZE to control rounding down of the > user-defined conring buffer size. What's wrong with the rounding? The more that, with the original behavior properly restored in patch 5, it'll be a power-of-2 multiple of PAGE_SIZE anyway? > Also, update the logline reporting the final conring buffer size to report > bytes instead of kilobytes, since the user-defined size may not necessarily > be kilobyte-alined. Yet making the number harder to grok. > Suggested-by: Andrew Cooper Having talked to him, I don't think he meant what you're doing here. All he apparently meant is to stop using alloc_*heap_pages(), which needlessly supplies order-aligned memory. > --- a/xen/drivers/char/Kconfig > +++ b/xen/drivers/char/Kconfig > @@ -95,6 +95,13 @@ config SERIAL_TX_BUFSIZE > > Default value is 32768 (32KiB). > > +config CONRING_ALIGN_PAGE_SIZE > + bool > + default y IOW "def_bool y". But what's the point of the option when there's no prompt? > --- a/xen/drivers/char/console.c > +++ b/xen/drivers/char/console.c > @@ -470,12 +470,15 @@ void __init console_init_ring(void) > return; > > opt_conring_size = max(opt_conring_size, conring_size); > - size = ROUNDDOWN(opt_conring_size, PAGE_SIZE); > - if ( size != opt_conring_size ) > + if ( IS_ENABLED(CONFIG_CONRING_ALIGN_PAGE_SIZE) ) > { > - opt_conring_size = size; > - printk(XENLOG_WARNING "Rounding down console ring size to multiple of %lu KiB.\n", > - PAGE_SIZE >> 10); > + size = ROUNDDOWN(opt_conring_size, PAGE_SIZE); > + if ( size != opt_conring_size ) > + { > + opt_conring_size = size; > + printk(XENLOG_WARNING "Rounding down console ring size to multiple of %lu KiB.\n", This line wants splitting at the start of the string literal, and the full stop wants removing if already it is being touched. Jan