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

Alex Williamson
2025-01-13T19:45:31Z

On Mon, 13 Jan 2025 08:34:41 -0500
Alex Williamson <alex.williamson@redhat.com> wrote:

> 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.

BTW, New->Old is not possible given the current old code and this
series doesn't enable it. New magic is saved, old restore could should
reject it:

static int vf_qm_check_match(struct hisi_acc_vf_core_device *hisi_acc_vdev,
struct hisi_acc_vf_migration_file *migf)
{
...
if (vf_data->acc_magic != ACC_DEV_MAGIC) {
dev_err(dev, "failed to match ACC_DEV_MAGIC\n");
return -EINVAL;
}

From this patch:

@@ -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

> >
> > 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