-----Original Message----- From: liulongfang <liulongfang@huawei.com> Sent: Tuesday, January 14, 2025 3:18 AM To: Alex Williamson <alex.williamson@redhat.com> Cc: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>; jgg@nvidia.com; Jonathan Cameron <jonathan.cameron@huawei.com>; kvm@vger.kernel.org; linux- kernel@vger.kernel.org; linuxarm@openeuler.org Subject: Re: [PATCH v2 1/5] hisi_acc_vfio_pci: fix XQE dma address error

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@@ -418,7 +440,7 @@ static int vf_qm_get_match_data(struct hisi_acc_vf_core_device *hisi_acc_vdev, int vf_id = hisi_acc_vdev->vf_id; int ret;

- vf_data->acc_magic = ACC_DEV_MAGIC; + vf_data->acc_magic = ACC_DEV_MAGIC_V2; /* Save device id */ vf_data->dev_id = hisi_acc_vdev->vf_dev->device;

Thanks, Alex

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As for the compatibility issues between old and new versions in the future, we do not need to reserve version numbers to deal with them now. Because before encountering specific problems, our design may

be redundant.

A magic value + version number would prevent the need to replace the magic value every time an issue is encountered, which I think was also Shameer's commit, which is not addressed by forcing the formatting of a portion of the magic value. None of what you're trying to do here precludes a new data structure for the new magic value or defining the padding fields for different use cases. Thanks,

Alex

If we want to use the original magic number, we also need to add the major and minor version numbers. It does not cause compatibility issues and can only reuse the original u64 memory space.

This is also Shameerali's previous plan. Do you accept this plan?

The suggestion here is to improve my previous plan.. ie, instead of overloading the V2 MAGIC with version info, introduce version(major:minor) separately. Something like, Rename old MAGIC as MAGIC_V1 Introduce new MAGIC as MAGIC_V2 Repurpose any padding or reserved fields in struct vf_data for major:minor version fields. The idea of introducing these major:minor is for future use where instead of coming up with a new MAGIC data every time we can increment the version for bug fixes and features if required. Hope this is clear now. Thanks, Shameer