Re: [PATCH v2 1/5] hisi_acc_vfio_pci: fix XQE dma address error

Alex Williamson
2025-01-13T13:34:59Z

On Mon, 13 Jan 2025 17:43:09 +0800
liulongfang <liulongfang@huawei.com> wrote:

> On 2025/1/3 6:30, Alex Williamson wrote:
> > On Thu, 19 Dec 2024 10:01:03 +0000
> > Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com> wrote:
> >
> >>> -----Original Message-----
> >>> From: liulongfang <liulongfang@huawei.com>
> >>> Sent: Thursday, December 19, 2024 9:18 AM
> >>> To: alex.williamson@redhat.com; jgg@nvidia.com; Shameerali Kolothum
> >>> Thodi <shameerali.kolothum.thodi@huawei.com>; Jonathan Cameron
> >>> <jonathan.cameron@huawei.com>
> >>> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org;
> >>> linuxarm@openeuler.org; liulongfang <liulongfang@huawei.com>
> >>> Subject: [PATCH v2 1/5] hisi_acc_vfio_pci: fix XQE dma address error
> >>>
> >>> 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 | 34 +++++++++++++++----
> >>> .../vfio/pci/hisilicon/hisi_acc_vfio_pci.h | 9 ++++-
> >>> 2 files changed, 36 insertions(+), 7 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..8518efea3a52 100644
> >>> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> >>> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> >>> @@ -350,6 +350,27 @@ 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_magic_check(struct acc_vf_data *vf_data)
> >>> +{
> >>> + switch (vf_data->acc_magic) {
> >>> + case ACC_DEV_MAGIC_V2:
> >>> + break;
> >>> + 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 +384,8 @@ 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_magic_check(vf_data);
> >>> + if (ret) {
> >>> dev_err(dev, "failed to match ACC_DEV_MAGIC\n");
> >>> return -EINVAL;
> >>> }
> >>> @@ -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;
> >>>
> >>> @@ -496,12 +518,12 @@ static int vf_qm_read_data(struct hisi_qm
> >>> *vf_qm, struct acc_vf_data *vf_data)
> >>> return -EINVAL;
> >>>
> >>> /* Every reg is 32 bit, the dma address is 64 bit. */
> >>> - vf_data->eqe_dma = vf_data->qm_eqc_dw[1];
> >>> + 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[0];
> >>> - vf_data->aeqe_dma = vf_data->qm_aeqc_dw[1];
> >>> + 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[0];
> >>> + vf_data->aeqe_dma |= vf_data-
> >>>> qm_aeqc_dw[QM_XQC_ADDR_LOW];
> >>>
> >>> /* Through SQC_BT/CQC_BT to get sqc and cqc address */
> >>> ret = qm_get_sqc(vf_qm, &vf_data->sqc_dma);
> >>> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> >>> b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> >>> index 245d7537b2bc..2afce68f5a34 100644
> >>> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> >>> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> >>> @@ -39,6 +39,9 @@
> >>> #define QM_REG_ADDR_OFFSET 0x0004
> >>>
> >>> #define QM_XQC_ADDR_OFFSET 32U
> >>> +#define QM_XQC_ADDR_LOW 0x1
> >>> +#define QM_XQC_ADDR_HIGH 0x2
> >>> +
> >>> #define QM_VF_AEQ_INT_MASK 0x0004
> >>> #define QM_VF_EQ_INT_MASK 0x000c
> >>> #define QM_IFC_INT_SOURCE_V 0x0020
> >>> @@ -50,10 +53,14 @@
> >>> #define QM_EQC_DW0 0X8000
> >>> #define QM_AEQC_DW0 0X8020
> >>>
> >>> +enum acc_magic_num {
> >>> + ACC_DEV_MAGIC_V1 = 0XCDCDCDCDFEEDAACC,
> >>> + ACC_DEV_MAGIC_V2 = 0xAACCFEEDDECADEDE,
> >>
> >>
> >> I think we have discussed this before that having some kind of
> >> version info embed into magic_num will be beneficial going
> >> forward. ie, may be use the last 4 bytes for denoting version.
> >>
> >> ACC_DEV_MAGIC_V2 = 0xAACCFEEDDECA0002
> >>
> >> The reason being, otherwise we have to come up with a random
> >> magic each time when a fix like this is required in future.
> >
> > Overloading the magic value like this is a bit strange. Typically
> > the magic value should be the cookie that identifies the data blob as
> > generated by this driver and a separate version field would identify
> > any content or format changes. In the mtty driver I included a magic
> > field along with major and minor versions to provide this flexibility.
> > I wonder why we wouldn't do something similar here rather than create
> > this combination magic/version field. It's easy enough to append a
> > couple fields onto the structure or redefine a v2 structure to use
> > going forward. There's even a padding field in the structure already
> > that could be repurposed.
> >
>
> If we add the major and minor version numbers like mtty driver, the current
> data structure needs to be changed, and this change also needs to be compatible
> with the old and new versions.
> And the old version does not have this information. The new version cannot
> be adapted when it is imported.

Are you suggesting that we cannot use a different data structure based
on the magic value? That's rather the point of the magic value.

> Now in this patch to fix this problem, we only need to update a magic number,
> and then the problem is corrected. Migration between old and new versions can
> also be fixed:
>
> Old --> Old, wrong, but we can't stop it;
> Old --> New, corrected migrated incorrect data, recovery successful;
> New --> New, correct, recovery successful;
> New --> Old, correct, recovery successful.
>
> 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