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Mon, 03 Feb 2025 08:31:11 -0800 (PST) Message-ID: <78a30e0b-5d79-4451-8fdc-99dfc7485b7d@suse.com> Date: Mon, 3 Feb 2025 17:31:09 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] xen/riscv: identify specific ISA supported by cpu To: Oleksii Kurochko Cc: Alistair Francis , Bob Eshleman , Connor Davis , Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Stefano Stabellini , xen-devel@lists.xenproject.org References: <4ee4c8c8-b392-4c0a-8173-624d661409f4@gmail.com> <99a1a2f6-12d7-4a4e-a776-05d6b960cf1d@suse.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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 03.02.2025 17:24, Oleksii Kurochko wrote: > On 2/3/25 5:03 PM, Jan Beulich wrote: >> On 03.02.2025 16:05, Oleksii Kurochko wrote: >>> On 1/27/25 3:47 PM, Jan Beulich wrote: >>>>> +static bool is_lowercase_extension_name(const char *str) >>>>> +{ >>>>> + /* >>>>> + * `str` could contain full riscv,isa string from device tree so one >>>>> + * of the stop condionitions is checking for '_' as extensions are >>>>> + * separated by '_'. >>>>> + */ >>>>> + for ( unsigned int i = 0; (str[i] != '\0') && (str[i] != '_'); i++ ) >>>>> + if ( !islower(str[i]) ) >>>>> + return false; >>>>> + >>>>> + return true; >>>>> +} >>>>> + >>>>> +static void __init match_isa_ext(const char *name, const char *name_end, >>>>> + unsigned long *bitmap) >>>>> +{ >>>>> + const size_t riscv_isa_ext_count = ARRAY_SIZE(riscv_isa_ext); >>>>> + >>>>> + for ( unsigned int i = 0; i < riscv_isa_ext_count; i++ ) >>>>> + { >>>>> + const struct riscv_isa_ext_data *ext = &riscv_isa_ext[i]; >>>>> + >>>>> + /* >>>>> + * `name` (according to device tree binding) and >>>>> + * `ext->name` (according to initialization of riscv_isa_ext[] >>>>> + * elements) must be all in lowercase. >>>>> + * >>>>> + * Just to be sure that it is true, ASSERT() is added. >>>>> + */ >>>>> + ASSERT(is_lowercase_extension_name(name) && >>>>> + is_lowercase_extension_name(ext->name)); >>>> More general remark: While asserting on ext->name is okay, for it being >>>> our own data, asserting on data coming from the outside is generally not >>>> correct. For now I'm not going to insist on this being changed, but >>>> sooner or later it will want revisiting >>> IIUC it would be better to leave ASSERT(is_lowercase_extension_name(ext->name)) in match_isa_ext() >>> and put ASSERT(is_lowercase_extension_name(ext) in riscv_isa_parse_string() before match_isa_ext() >>> is called: >>> static int __init riscv_isa_parse_string(const char *isa, >>> unsigned long *out_bitmap) >>> { >>> ... >>> while ( *isa ) >>> { >>> const char *ext = isa++; >>> ... >>> ASSERT(is_lowercase_extension_name(ext)); >>> match_isa_ext(ext, ext_end, out_bitmap); >>> } >>> >>> Is my understanding correct? >> That depends on the origin of the incoming "isa". Considering the function >> wants to parse it, I'd expect it still comes from DT. In which case >> asserting on it is wrong; anything may come from there, and nothing should >> cause assertion failures. Recall that assertions are checks of _our own >> internal state_ only. > > But based on the device tree binding (https://elixir.bootlin.com/linux/v6.13.1/source/Documentation/devicetree/bindings/riscv/extensions.yaml#L47 ), > not anything should come from DT for the riscv,isa string; only lowercase letters are allowed. > I am not sure if it makes sense to double-check if riscv,isa is correct, as my expectation (which I haven’t checked yet) is that the DTS will > be validated during compilation. > > Does it make sense to double check what was put in DT's riscv,isa? I think so. Just not by way of an assertion. Jan