[{"id":3677888,"web_url":"http://patchwork.ozlabs.org/comment/3677888/","msgid":"<44d27b03-0d16-4114-9565-ee01e8d6189e@huawei.com>","list_archive_url":null,"date":"2026-04-16T01:16:15","subject":"Re: [PATCH 4/4] vfio/pci: Add PCIe TPH SET_ST interface","submitter":{"id":92756,"url":"http://patchwork.ozlabs.org/api/people/92756/","name":"fengchengwen","email":"fengchengwen@huawei.com"},"content":"On 4/15/2026 10:01 PM, Wathsala Vithanage wrote:\n>>   +static int vfio_pci_tph_set_st(struct vfio_pci_core_device *vdev,\n>> +                   struct vfio_device_pci_tph_op *op,\n>> +                   void __user *uarg)\n>> +{\n>> +    struct vfio_pci_tph_entry *ents;\n>> +    struct vfio_pci_tph_st st;\n>> +    enum tph_mem_type mtype;\n>> +    int i, err, size;\n>> +    u16 st_val;\n>> +\n>> +    if (copy_from_user(&st, uarg, sizeof(st)))\n>> +        return -EFAULT;\n>> +\n>> +    if (!st.count || st.count > 2048)\n>> +        return -EINVAL;\n>> +\n>> +    size = st.count * sizeof(*ents);\n>> +    ents = kvmalloc(size, GFP_KERNEL);\n>> +    if (!ents)\n>> +        return -ENOMEM;\n>> +\n>> +    if (copy_from_user(ents, uarg + sizeof(st), size)) {\n>> +        err = -EFAULT;\n>> +        goto out;\n>> +    }\n>> +\n>> +    for (i = 0; i < st.count; i++) {\n>> +        if (ents[i].mem_type == VFIO_PCI_TPH_MEM_TYPE_VM) {\n>> +            mtype = TPH_MEM_TYPE_VM;\n>> +        } else if (ents[i].mem_type == VFIO_PCI_TPH_MEM_TYPE_PM) {\n>> +            mtype = TPH_MEM_TYPE_PM;\n>> +        } else {\n>> +            err = -EINVAL;\n>> +            goto out;\n>> +        }\n>> +\n>> +        err = pcie_tph_get_cpu_st(vdev->pdev, mtype, ents[i].cpu, &st_val);\n>> +        if (err)\n>> +            goto out;\n>> +        err = pcie_tph_set_st_entry(vdev->pdev, ents[i].index, st_val);\n>> +        if (err)\n>> +            goto out;\n>> +    }\n> \n> We also dropped batched updates of steering tags because there is no way a user could tell\n> which entry failed unless struct vfio_pci_tph_entry had an error field. But, we thought the\n> added complexity is not justified as these calls are only used during initialization.\n\nThank you for the feedback on batched steering tag updates.\n\nI agree that per-entry error reporting adds unnecessary\ncomplexity, especially for initialization-time operations.\n\nTo keep things simple and robust, the next version batch\nimplementation will use a straightforward failure model:\n if programming any ST entry fails, the kernel will roll\n back all previously programmed entries by clearing them\n to 0, then return an error to userspace.\n\nThis avoids partial programming states, requires no per-entry\nerror fields, and fits well with one-shot device initialization.\n\nThanks\n\n> \n> --wathsala","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=huawei.com header.i=@huawei.com header.a=rsa-sha256\n header.s=dkim header.b=UQnetT4U;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.234.253.10; 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a=rsa-sha256; d=huawei.com; s=dkim;\n\tc=relaxed/relaxed; q=dns/txt;\n\th=From;\n\tbh=MGT+QgMDGRLeV/oInIFWFUL4aCEDD9cQy1MPH8ZCZWk=;\n\tb=UQnetT4UB7zPkbAqQXCf9fjgedJh0Z5VEIwwsq3H74aHBhFxWVxnFfx9HjnwNPT4yNvpxOVvv\n\tMI6h/XL1v8DtdnRVftnqPrcmYy7h0x1/BX7L0C/UChf085SwUo5sJR/r2VCfjYy0iItiw8HR5C1\n\tc20BEC9j41ampPq0pGzNEb8=","Message-ID":"<44d27b03-0d16-4114-9565-ee01e8d6189e@huawei.com>","Date":"Thu, 16 Apr 2026 09:16:15 +0800","Precedence":"bulk","X-Mailing-List":"linux-pci@vger.kernel.org","List-Id":"","List-Subscribe":"","List-Unsubscribe":"","MIME-Version":"1.0","User-Agent":"Mozilla Thunderbird","Subject":"Re: [PATCH 4/4] vfio/pci: Add PCIe TPH SET_ST interface","To":"Wathsala Vithanage , ,\n\t","CC":", ","References":"<20260415090959.53672-1-fengchengwen@huawei.com>\n <20260415090959.53672-5-fengchengwen@huawei.com>\n ","Content-Language":"en-US","From":"fengchengwen ","In-Reply-To":"","Content-Type":"text/plain; charset=\"UTF-8\"","Content-Transfer-Encoding":"8bit","X-ClientProxiedBy":"kwepems200001.china.huawei.com (7.221.188.67) To\n kwepemk500009.china.huawei.com (7.202.194.94)"}}]