Re: [PATCH v4 1/5] hisi_acc_vfio_pci: fix XQE dma address error

liulongfang
2025-02-26T11:41:46Z

On 2025/2/26 16:11, Shameerali Kolothum Thodi wrote:
>
>
>> -----Original Message-----
>> From: Alex Williamson <alex.williamson@redhat.com>
>> Sent: Wednesday, February 26, 2025 12:10 AM
>> To: liulongfang <liulongfang@huawei.com>
>> Cc: jgg@nvidia.com; Shameerali Kolothum Thodi
>> <shameerali.kolothum.thodi@huawei.com>; Jonathan Cameron
>> <jonathan.cameron@huawei.com>; kvm@vger.kernel.org; linux-
>> kernel@vger.kernel.org; linuxarm@openeuler.org
>> Subject: Re: [PATCH v4 1/5] hisi_acc_vfio_pci: fix XQE dma address error
>>
>> On Tue, 25 Feb 2025 14:27:53 +0800
>> Longfang Liu <liulongfang@huawei.com> wrote:
>>
>>> The dma addresses of EQE and AEQE are wrong after migration and
>>> results in guest kernel-mode encryption services failure.
>>> Comparing the definition of hardware registers, we found that
>>> there was an error when the data read from the register was
>>> combined into an address. Therefore, the address combination
>>> sequence needs to be corrected.
>>>
>>> Even after fixing the above problem, we still have an issue
>>> where the Guest from an old kernel can get migrated to
>>> new kernel and may result in wrong data.
>>>
>>> In order to ensure that the address is correct after migration,
>>> if an old magic number is detected, the dma address needs to be
>>> updated.
>>>
>>> Fixes: b0eed085903e ("hisi_acc_vfio_pci: Add support for VFIO live
>> migration")
>>> Signed-off-by: Longfang Liu <liulongfang@huawei.com>
>>> ---
>>> .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c | 40 ++++++++++++++++---
>>> .../vfio/pci/hisilicon/hisi_acc_vfio_pci.h | 14 ++++++-
>>> 2 files changed, 46 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>>> index 451c639299eb..35316984089b 100644
>>> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>>> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>>> @@ -350,6 +350,31 @@ static int vf_qm_func_stop(struct hisi_qm *qm)
>>> return hisi_qm_mb(qm, QM_MB_CMD_PAUSE_QM, 0, 0, 0);
>>> }
>>>
>>> +static int vf_qm_version_check(struct acc_vf_data *vf_data, struct device
>> *dev)
>>> +{
>>> + switch (vf_data->acc_magic) {
>>> + case ACC_DEV_MAGIC_V2:
>>> + if (vf_data->major_ver < ACC_DRV_MAJOR_VER ||
>>> + vf_data->minor_ver < ACC_DRV_MINOR_VER)
>>> + dev_info(dev, "migration driver version not
>> match!\n");
>>> + return -EINVAL;
>>> + break;
>>
>> What's your major/minor update strategy?
>>
>> Note that minor_ver is a u16 and ACC_DRV_MINOR_VER is defined as 0, so
>> testing less than 0 against an unsigned is useless.
>>
>> Arguably testing major and minor independently is pretty useless too.
>>
>> You're defining what a future "old" driver version will accept, which
>> is very nearly anything, so any breaking change *again* requires a new
>> magic, so we're accomplishing very little here.
>>
>> Maybe you want to consider a strategy where you'd increment the major
>> number for a breaking change and minor for a compatible feature. In
>> that case you'd want to verify the major_ver matches
>> ACC_DRV_MAJOR_VER
>> exactly and minor_ver would be more of a feature level.
>
> Agree. I think the above check should be just major_ver != ACC_DRV_MAJOR_VER
> and we can make use of minor version whenever we need a specific handling for
> a feature support.
>

Well, that's a good way.
We only use minor_ver to record important updates of the driver. When there is
an important update, minor_ver increases by 1.
Major_ver is used to distinguish migration versions. After major_ver is updated,
minor_ver returns to 0.

Therefore, we can change it to only check major_ver.

> Also I think it would be good to print the version info above in case of mismatch.
>

OK.
Thanks.
Longfang.

>>
>>> + case ACC_DEV_MAGIC_V1:
>>> + /* Correct dma address */
>>> + vf_data->eqe_dma = vf_data-
>>> qm_eqc_dw[QM_XQC_ADDR_HIGH];
>>> + vf_data->eqe_dma <<= QM_XQC_ADDR_OFFSET;
>>> + vf_data->eqe_dma |= vf_data-
>>> qm_eqc_dw[QM_XQC_ADDR_LOW];
>>> + vf_data->aeqe_dma = vf_data-
>>> qm_aeqc_dw[QM_XQC_ADDR_HIGH];
>>> + vf_data->aeqe_dma <<= QM_XQC_ADDR_OFFSET;
>>> + vf_data->aeqe_dma |= vf_data-
>>> qm_aeqc_dw[QM_XQC_ADDR_LOW];
>>> + break;
>>> + default:
>>> + return -EINVAL;
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +
>>> static int vf_qm_check_match(struct hisi_acc_vf_core_device
>> *hisi_acc_vdev,
>>> struct hisi_acc_vf_migration_file *migf)
>>> {
>>> @@ -363,7 +388,8 @@ static int vf_qm_check_match(struct
>> hisi_acc_vf_core_device *hisi_acc_vdev,
>>> if (migf->total_length < QM_MATCH_SIZE || hisi_acc_vdev-
>>> match_done)
>>> return 0;
>>>
>>> - if (vf_data->acc_magic != ACC_DEV_MAGIC) {
>>> + ret = vf_qm_version_check(vf_data, dev);
>>> + if (ret) {
>>> dev_err(dev, "failed to match ACC_DEV_MAGIC\n");
>>> return -EINVAL;
>>> }
>>> @@ -418,7 +444,9 @@ 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;
>>> + vf_data->major_ver = ACC_DRV_MAR;
>>> + vf_data->minor_ver = ACC_DRV_MIN;
>>
>> Where are "MAR" and "MIN" defined? I can't see how this would even
>> compile. Thanks,
>
> Yes. Please make sure to do a compile test and run basic sanity tested even if you
> think the changes are minor. Chances are there that you will miss out things like
> this.
>
> Thanks,
> Shameer
>
> .
>