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Message-ID: <5ad84261-fead-42ae-ac6c-8ecf17db7462@intel.com>
Date: Thu, 23 Oct 2025 00:49:52 +0200
From: Michal Wajdeczko <michal.wajdeczko@...el.com>
To: Michał Winiarski <michal.winiarski@...el.com>, "Alex
Williamson" <alex.williamson@...hat.com>, Lucas De Marchi
<lucas.demarchi@...el.com>, Thomas Hellström
<thomas.hellstrom@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
Jason Gunthorpe <jgg@...pe.ca>, Yishai Hadas <yishaih@...dia.com>, Kevin Tian
<kevin.tian@...el.com>, <intel-xe@...ts.freedesktop.org>,
<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>, Matthew Brost
<matthew.brost@...el.com>
CC: <dri-devel@...ts.freedesktop.org>, Jani Nikula
<jani.nikula@...ux.intel.com>, Joonas Lahtinen
<joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin <tursulin@...ulin.net>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, "Lukasz
Laguna" <lukasz.laguna@...el.com>
Subject: Re: [PATCH v2 07/26] drm/xe/pf: Add minimalistic migration descriptor
On 10/22/2025 12:41 AM, Michał Winiarski wrote:
> The descriptor reuses the KLV format used by GuC and contains metadata
> that can be used to quickly fail migration when source is incompatible
> with destination.
>
> Signed-off-by: Michał Winiarski <michal.winiarski@...el.com>
> ---
> drivers/gpu/drm/xe/xe_sriov_migration_data.c | 79 +++++++++++++++++++-
> drivers/gpu/drm/xe/xe_sriov_migration_data.h | 2 +
> drivers/gpu/drm/xe/xe_sriov_pf_migration.c | 6 ++
> 3 files changed, 86 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_sriov_migration_data.c b/drivers/gpu/drm/xe/xe_sriov_migration_data.c
> index 4cd6c6fc9ba18..b58508c0c30f1 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_migration_data.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_migration_data.c
> @@ -5,6 +5,7 @@
>
> #include "xe_bo.h"
> #include "xe_device.h"
> +#include "xe_guc_klv_helpers.h"
> #include "xe_sriov_migration_data.h"
> #include "xe_sriov_pf_helpers.h"
> #include "xe_sriov_pf_migration.h"
> @@ -383,11 +384,18 @@ ssize_t xe_sriov_migration_data_write(struct xe_device *xe, unsigned int vfid,
> return produced;
> }
>
> -#define MIGRATION_DESCRIPTOR_DWORDS 0
> +#define MIGRATION_KLV_DEVICE_DEVID_KEY 0xf001u
> +#define MIGRATION_KLV_DEVICE_DEVID_LEN 1u
> +#define MIGRATION_KLV_DEVICE_REVID_KEY 0xf002u
> +#define MIGRATION_KLV_DEVICE_REVID_LEN 1u
> +
> +#define MIGRATION_DESCRIPTOR_DWORDS (GUC_KLV_LEN_MIN + MIGRATION_KLV_DEVICE_DEVID_LEN + \
> + GUC_KLV_LEN_MIN + MIGRATION_KLV_DEVICE_REVID_LEN)
> static size_t pf_descriptor_init(struct xe_device *xe, unsigned int vfid)
> {
> struct xe_sriov_migration_data **desc = pf_pick_descriptor(xe, vfid);
> struct xe_sriov_migration_data *data;
> + u32 *klvs;
> int ret;
>
> data = xe_sriov_migration_data_alloc(xe);
> @@ -401,11 +409,80 @@ static size_t pf_descriptor_init(struct xe_device *xe, unsigned int vfid)
> return ret;
> }
>
> + klvs = data->vaddr;
> + *klvs++ = PREP_GUC_KLV_CONST(MIGRATION_KLV_DEVICE_DEVID_KEY,
> + MIGRATION_KLV_DEVICE_DEVID_LEN);
> + *klvs++ = xe->info.devid;
> + *klvs++ = PREP_GUC_KLV_CONST(MIGRATION_KLV_DEVICE_REVID_KEY,
> + MIGRATION_KLV_DEVICE_REVID_LEN);
> + *klvs++ = xe->info.revid;
> +
maybe add assert that written KLVs match descriptor size?
> *desc = data;
>
> return 0;
> }
>
> +/**
> + * xe_sriov_migration_data_process_descriptor() - Process migration data descriptor.
> + * @xe: the &xe_device
> + * @vfid: the VF identifier
> + * @data: the &struct xe_sriov_pf_migration_data containing the descriptor
> + *
> + * The descriptor uses the same KLV format as GuC, and contains metadata used for
> + * checking migration data compatibility.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int xe_sriov_migration_data_process_descriptor(struct xe_device *xe, unsigned int vfid,
> + struct xe_sriov_migration_data *data)
> +{
> + u32 num_dwords = data->size / sizeof(u32);
> + u32 *klvs = data->vaddr;
> +
> + xe_assert(xe, data->type == XE_SRIOV_MIGRATION_DATA_TYPE_DESCRIPTOR);
> + if (data->size % sizeof(u32) != 0)
no need to compare against 0
if (data->size % sizeof(u32))
> + return -EINVAL;
for other errors we warn(), ok to be silent here?
> +
> + while (num_dwords >= GUC_KLV_LEN_MIN) {
> + u32 key = FIELD_GET(GUC_KLV_0_KEY, klvs[0]);
> + u32 len = FIELD_GET(GUC_KLV_0_LEN, klvs[0]);
> +
> + klvs += GUC_KLV_LEN_MIN;
> + num_dwords -= GUC_KLV_LEN_MIN;
> +
you should check len vs num_dwords here
> + switch (key) {
> + case MIGRATION_KLV_DEVICE_DEVID_KEY:
> + if (*klvs != xe->info.devid) {
> + xe_sriov_warn(xe,
> + "Aborting migration, devid mismatch %#04x!=%#04x\n",
likely %#06x, as you need to count also "0x"
> + *klvs, xe->info.devid);
> + return -ENODEV;
> + }
> + break;
> + case MIGRATION_KLV_DEVICE_REVID_KEY:
> + if (*klvs != xe->info.revid) {
> + xe_sriov_warn(xe,
> + "Aborting migration, revid mismatch %#04x!=%#04x\n",
> + *klvs, xe->info.revid);
> + return -ENODEV;
> + }
> + break;
> + default:
> + xe_sriov_dbg(xe,
> + "Unknown migration descriptor key %#06x - skipping\n", key);
also print len? and some initial hexdump to help with debug?
> + break;
> + }
> +
> + if (len > num_dwords)
> + return -EINVAL;
this check should be earlier
> +
> + klvs += len;
> + num_dwords -= len;
> + }
> +
> + return 0;
> +}
> +
> static void pf_pending_init(struct xe_device *xe, unsigned int vfid)
> {
> struct xe_sriov_migration_data **data = pf_pick_pending(xe, vfid);
> diff --git a/drivers/gpu/drm/xe/xe_sriov_migration_data.h b/drivers/gpu/drm/xe/xe_sriov_migration_data.h
> index 5cde6e9439677..e7f3b332124bc 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_migration_data.h
> +++ b/drivers/gpu/drm/xe/xe_sriov_migration_data.h
> @@ -31,6 +31,8 @@ ssize_t xe_sriov_migration_data_read(struct xe_device *xe, unsigned int vfid,
> char __user *buf, size_t len);
> ssize_t xe_sriov_migration_data_write(struct xe_device *xe, unsigned int vfid,
> const char __user *buf, size_t len);
> +int xe_sriov_migration_data_process_descriptor(struct xe_device *xe, unsigned int vfid,
> + struct xe_sriov_migration_data *data);
> int xe_sriov_migration_data_save_init(struct xe_device *xe, unsigned int vfid);
>
> #endif
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_migration.c b/drivers/gpu/drm/xe/xe_sriov_pf_migration.c
> index 029e14f1ffa74..0b4b237780102 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_migration.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_migration.c
> @@ -176,9 +176,15 @@ xe_sriov_pf_migration_save_consume(struct xe_device *xe, unsigned int vfid)
> static int pf_handle_descriptor(struct xe_device *xe, unsigned int vfid,
> struct xe_sriov_migration_data *data)
> {
> + int ret;
> +
> if (data->tile != 0 || data->gt != 0)
> return -EINVAL;
>
> + ret = xe_sriov_migration_data_process_descriptor(xe, vfid, data);
> + if (ret)
> + return ret;
> +
> xe_sriov_migration_data_free(data);
>
> return 0;
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