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AKwUvBxSQfLM+pSBsWwLDQqdhFvHYWEK5ShcoHf624hzCUPw5bLsuHTN3WmCzhjO/iPfStbZzze/7e89Kjc=@lists.xenproject.org X-Gm-Message-State: AFuF++nuxF9Pi77SI6pKbvHL2pVFWoJihT/fh0zMFz+Vjg3Q+265DQP9 Jh75WMnxVBJircuKHiKJ8Uk3/dEXy1SKY8Nm9UTpNQaYurRT49yUJU2h7u7JW0jIhg== X-Gm-Gg: AYBFou2Zas6637nMpyZScXoax0MuOeJ61HpaiFapH/WHA6W0v1avZQMJYWWSSJ55YRG BVYm6JYnuH7ZMAJ9f03LlOc33haF9sUgC8uivfF92vJUi7y7jGqohnzkD9LI4jF34pSuk1qjG1C wkoosoBK14uu1sP4/KBqQOJz4teSn7lpWP4sK3BLLJwcRLb5VJKqq3/GltPTyR3pbXisQYy+5w4 3M0ztRmNueOObP7Ye3QFfwRPyKkf6UGxVJR+bQE4WuIq0QamPZ/vqqtIzWFfRt3xmou9Ey23+5E rwUhuYl0sewtCBnjZ3RVsQjPAsAQ7BIZwCsGhu3/531MwR4yPBVpIoPBXUXV1NJ2elh7tGygwQ8 tBLFBQTMeAz115S5bhKvHYCuem+9qzx3YWwKeCbt7lxwKJI5PVkyxP9zfpyZfWp0YlYPoHbiWCh j/8hLALRatm1PleTcijV9sJbJPg7QWwrTgF0yJZYyGYAMN0Gx2Te40nYLSzIKQ+6O8RZtdDrkrT vA/LaYQNyHy4JztjvKDE6VMD3BDbAieR+hsATpe/AGVAJqg9WtKB4IzQXrTnB4= X-Received: by 2002:a05:600c:4fcb:b0:49c:f13e:e4c with SMTP id 5b1f17b1804b1-49d26db4274mr43955165e9.9.1789039415489; Thu, 10 Sep 2026 04:23:35 -0700 (PDT) Message-ID: <9f2245d8-faef-4608-a179-b8e942fdfc1d@suse.com> Date: Thu, 10 Sep 2026 13:23:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 10/39] xen/riscv: build the target hart index via aplic_hart_field() To: Oleksii Kurochko Cc: Romain Caritey , Baptiste Le Duc , Zheng Zhang , Alistair Francis , 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: <3c7418d64a730ec5e4b2cfd0ecfbbbc6fe0bf7d8.1787838835.git.oleksii.kurochko@gmail.com> <487a7efa-e83d-4ae2-8f39-33483161a64d@gmail.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: <487a7efa-e83d-4ae2-8f39-33483161a64d@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-720697/1789039416-F34BE2AC-CCA6E352/0/0 X-purgate-type: clean X-purgate-size: 2671 On 10.09.2026 12:59, Oleksii Kurochko wrote: > On 9/9/26 4:52 PM, Jan Beulich wrote: >> On 27.08.2026 17:20, Oleksii Kurochko wrote: >>> @@ -340,27 +338,11 @@ static void cf_check aplic_set_irq_affinity(struct irq_desc *desc, const cpumask >>> >>> ASSERT(spin_is_locked(&desc->lock)); >>> >>> - cpu = cpuid_to_hartid(aplic_get_cpu_from_mask(mask)); >>> - hhxw = imsic->group_index_bits; >>> - lhxw = imsic->hart_index_bits; >>> - /* >>> - * Although this variable is used only once in the calculation of >>> - * group_index, and it might seem that hhxs could be defined as: >>> - * hhxs = imsic->group_index_shift - IMSIC_MMIO_PAGE_SHIFT; >>> - * and then the addition of IMSIC_MMIO_PAGE_SHIFT could be omitted >>> - * when calculating the group index. >>> - * It was done intentionally this way to follow the formula from >>> - * the AIA specification for calculating the MSI address. >>> - */ >>> - hhxs = imsic->group_index_shift - IMSIC_MMIO_PAGE_SHIFT * 2; >>> - base_ppn = imsic->msi[cpu].base_addr >> IMSIC_MMIO_PAGE_SHIFT; >>> - >>> - /* Update hart and EEID in the target register */ >>> - group_index = (base_ppn >> (hhxs + IMSIC_MMIO_PAGE_SHIFT)) & >>> - (BIT(hhxw, UL) - 1); >>> - value = desc->irq; >> >> Hmm, only after sending the ack I noticed that there's no masking here, ... >> >>> - value |= cpu << APLIC_TARGET_HART_IDX_SHIFT; >>> - value |= group_index << (lhxw + APLIC_TARGET_HART_IDX_SHIFT); >>> + cpu = aplic_get_cpu_from_mask(mask); >>> + >>> + /* Update hart index and EIID in the target register */ >>> + value = MASK_INSR(aplic_hart_field(cpu), APLIC_TARGET_HART_IDX) | >>> + (desc->irq & APLIC_TARGET_EIID); >> >> ... but there is masking here. Chopping off bits doesn't look as if it can >> lead to anything good. What's the deal here? > > The mask is a no-op: desc->irq < NR_IRQS (1024) always fits the 11-bit > EIID field, so I'll drop it and add a BUILD_BUG_ON() instead. > > Would it be better to: > > + /* desc->irq < NR_IRQS, so it always fits the EIID field */ > + BUILD_BUG_ON(NR_IRQS - 1 > APLIC_TARGET_EIID); If the question is whether to prefer BUILD_BUG_ON() over BUG_ON(), then: Yes please. However, APLIC_TARGET_EIID is a mask (despite its name not indicating that), which only happens to start at bit 0. This kind of assumption would better be avoided. This raises another question though: No matter how big a RISC-V system is, it can only ever have 1k IRQs? How does that work with a single MSI-X device having up to 2k MSIs? Jan Jan