vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console

[linux/fpc-iii.git] / drivers / gpu / drm / i915 / intel_guc.c

/*
 * Copyright © 2014-2017 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 */

#include "intel_guc.h"
#include "intel_guc_ads.h"
#include "intel_guc_submission.h"
#include "i915_drv.h"

static void guc_init_ggtt_pin_bias(struct intel_guc *guc);

static void gen8_guc_raise_irq(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);

        I915_WRITE(GUC_SEND_INTERRUPT, GUC_SEND_TRIGGER);
}

static inline i915_reg_t guc_send_reg(struct intel_guc *guc, u32 i)
{
        GEM_BUG_ON(!guc->send_regs.base);
        GEM_BUG_ON(!guc->send_regs.count);
        GEM_BUG_ON(i >= guc->send_regs.count);

        return _MMIO(guc->send_regs.base + 4 * i);
}

void intel_guc_init_send_regs(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        enum forcewake_domains fw_domains = 0;
        unsigned int i;

        guc->send_regs.base = i915_mmio_reg_offset(SOFT_SCRATCH(0));
        guc->send_regs.count = SOFT_SCRATCH_COUNT - 1;

        for (i = 0; i < guc->send_regs.count; i++) {
                fw_domains |= intel_uncore_forcewake_for_reg(dev_priv,
                                        guc_send_reg(guc, i),
                                        FW_REG_READ | FW_REG_WRITE);
        }
        guc->send_regs.fw_domains = fw_domains;
}

void intel_guc_init_early(struct intel_guc *guc)
{
        intel_guc_fw_init_early(guc);
        intel_guc_ct_init_early(&guc->ct);
        intel_guc_log_init_early(&guc->log);

        mutex_init(&guc->send_mutex);
        spin_lock_init(&guc->irq_lock);
        guc->send = intel_guc_send_nop;
        guc->handler = intel_guc_to_host_event_handler_nop;
        guc->notify = gen8_guc_raise_irq;
}

static int guc_init_wq(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);

        /*
         * GuC log buffer flush work item has to do register access to
         * send the ack to GuC and this work item, if not synced before
         * suspend, can potentially get executed after the GFX device is
         * suspended.
         * By marking the WQ as freezable, we don't have to bother about
         * flushing of this work item from the suspend hooks, the pending
         * work item if any will be either executed before the suspend
         * or scheduled later on resume. This way the handling of work
         * item can be kept same between system suspend & rpm suspend.
         */
        guc->log.relay.flush_wq =
                alloc_ordered_workqueue("i915-guc_log",
                                        WQ_HIGHPRI | WQ_FREEZABLE);
        if (!guc->log.relay.flush_wq) {
                DRM_ERROR("Couldn't allocate workqueue for GuC log\n");
                return -ENOMEM;
        }

        /*
         * Even though both sending GuC action, and adding a new workitem to
         * GuC workqueue are serialized (each with its own locking), since
         * we're using mutliple engines, it's possible that we're going to
         * issue a preempt request with two (or more - each for different
         * engine) workitems in GuC queue. In this situation, GuC may submit
         * all of them, which will make us very confused.
         * Our preemption contexts may even already be complete - before we
         * even had the chance to sent the preempt action to GuC!. Rather
         * than introducing yet another lock, we can just use ordered workqueue
         * to make sure we're always sending a single preemption request with a
         * single workitem.
         */
        if (HAS_LOGICAL_RING_PREEMPTION(dev_priv) &&
            USES_GUC_SUBMISSION(dev_priv)) {
                guc->preempt_wq = alloc_ordered_workqueue("i915-guc_preempt",
                                                          WQ_HIGHPRI);
                if (!guc->preempt_wq) {
                        destroy_workqueue(guc->log.relay.flush_wq);
                        DRM_ERROR("Couldn't allocate workqueue for GuC "
                                  "preemption\n");
                        return -ENOMEM;
                }
        }

        return 0;
}

static void guc_fini_wq(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);

        if (HAS_LOGICAL_RING_PREEMPTION(dev_priv) &&
            USES_GUC_SUBMISSION(dev_priv))
                destroy_workqueue(guc->preempt_wq);

        destroy_workqueue(guc->log.relay.flush_wq);
}

int intel_guc_init_misc(struct intel_guc *guc)
{
        struct drm_i915_private *i915 = guc_to_i915(guc);
        int ret;

        guc_init_ggtt_pin_bias(guc);

        ret = guc_init_wq(guc);
        if (ret)
                return ret;

        intel_uc_fw_fetch(i915, &guc->fw);

        return 0;
}

void intel_guc_fini_misc(struct intel_guc *guc)
{
        intel_uc_fw_fini(&guc->fw);
        guc_fini_wq(guc);
}

static int guc_shared_data_create(struct intel_guc *guc)
{
        struct i915_vma *vma;
        void *vaddr;

        vma = intel_guc_allocate_vma(guc, PAGE_SIZE);
        if (IS_ERR(vma))
                return PTR_ERR(vma);

        vaddr = i915_gem_object_pin_map(vma->obj, I915_MAP_WB);
        if (IS_ERR(vaddr)) {
                i915_vma_unpin_and_release(&vma);
                return PTR_ERR(vaddr);
        }

        guc->shared_data = vma;
        guc->shared_data_vaddr = vaddr;

        return 0;
}

static void guc_shared_data_destroy(struct intel_guc *guc)
{
        i915_gem_object_unpin_map(guc->shared_data->obj);
        i915_vma_unpin_and_release(&guc->shared_data);
}

int intel_guc_init(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        int ret;

        ret = guc_shared_data_create(guc);
        if (ret)
                goto err_fetch;
        GEM_BUG_ON(!guc->shared_data);

        ret = intel_guc_log_create(&guc->log);
        if (ret)
                goto err_shared;

        ret = intel_guc_ads_create(guc);
        if (ret)
                goto err_log;
        GEM_BUG_ON(!guc->ads_vma);

        /* We need to notify the guc whenever we change the GGTT */
        i915_ggtt_enable_guc(dev_priv);

        return 0;

err_log:
        intel_guc_log_destroy(&guc->log);
err_shared:
        guc_shared_data_destroy(guc);
err_fetch:
        intel_uc_fw_fini(&guc->fw);
        return ret;
}

void intel_guc_fini(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);

        i915_ggtt_disable_guc(dev_priv);
        intel_guc_ads_destroy(guc);
        intel_guc_log_destroy(&guc->log);
        guc_shared_data_destroy(guc);
        intel_uc_fw_fini(&guc->fw);
}

static u32 guc_ctl_debug_flags(struct intel_guc *guc)
{
        u32 level = intel_guc_log_get_level(&guc->log);
        u32 flags;
        u32 ads;

        ads = intel_guc_ggtt_offset(guc, guc->ads_vma) >> PAGE_SHIFT;
        flags = ads << GUC_ADS_ADDR_SHIFT | GUC_ADS_ENABLED;

        if (!GUC_LOG_LEVEL_IS_ENABLED(level))
                flags |= GUC_LOG_DEFAULT_DISABLED;

        if (!GUC_LOG_LEVEL_IS_VERBOSE(level))
                flags |= GUC_LOG_DISABLED;
        else
                flags |= GUC_LOG_LEVEL_TO_VERBOSITY(level) <<
                         GUC_LOG_VERBOSITY_SHIFT;

        return flags;
}

static u32 guc_ctl_feature_flags(struct intel_guc *guc)
{
        u32 flags = 0;

        flags |=  GUC_CTL_VCS2_ENABLED;

        if (USES_GUC_SUBMISSION(guc_to_i915(guc)))
                flags |= GUC_CTL_KERNEL_SUBMISSIONS;
        else
                flags |= GUC_CTL_DISABLE_SCHEDULER;

        return flags;
}

static u32 guc_ctl_ctxinfo_flags(struct intel_guc *guc)
{
        u32 flags = 0;

        if (USES_GUC_SUBMISSION(guc_to_i915(guc))) {
                u32 ctxnum, base;

                base = intel_guc_ggtt_offset(guc, guc->stage_desc_pool);
                ctxnum = GUC_MAX_STAGE_DESCRIPTORS / 16;

                base >>= PAGE_SHIFT;
                flags |= (base << GUC_CTL_BASE_ADDR_SHIFT) |
                        (ctxnum << GUC_CTL_CTXNUM_IN16_SHIFT);
        }
        return flags;
}

static u32 guc_ctl_log_params_flags(struct intel_guc *guc)
{
        u32 offset = intel_guc_ggtt_offset(guc, guc->log.vma) >> PAGE_SHIFT;
        u32 flags;

        #if (((CRASH_BUFFER_SIZE) % SZ_1M) == 0)
        #define UNIT SZ_1M
        #define FLAG GUC_LOG_ALLOC_IN_MEGABYTE
        #else
        #define UNIT SZ_4K
        #define FLAG 0
        #endif

        BUILD_BUG_ON(!CRASH_BUFFER_SIZE);
        BUILD_BUG_ON(!IS_ALIGNED(CRASH_BUFFER_SIZE, UNIT));
        BUILD_BUG_ON(!DPC_BUFFER_SIZE);
        BUILD_BUG_ON(!IS_ALIGNED(DPC_BUFFER_SIZE, UNIT));
        BUILD_BUG_ON(!ISR_BUFFER_SIZE);
        BUILD_BUG_ON(!IS_ALIGNED(ISR_BUFFER_SIZE, UNIT));

        BUILD_BUG_ON((CRASH_BUFFER_SIZE / UNIT - 1) >
                        (GUC_LOG_CRASH_MASK >> GUC_LOG_CRASH_SHIFT));
        BUILD_BUG_ON((DPC_BUFFER_SIZE / UNIT - 1) >
                        (GUC_LOG_DPC_MASK >> GUC_LOG_DPC_SHIFT));
        BUILD_BUG_ON((ISR_BUFFER_SIZE / UNIT - 1) >
                        (GUC_LOG_ISR_MASK >> GUC_LOG_ISR_SHIFT));

        flags = GUC_LOG_VALID |
                GUC_LOG_NOTIFY_ON_HALF_FULL |
                FLAG |
                ((CRASH_BUFFER_SIZE / UNIT - 1) << GUC_LOG_CRASH_SHIFT) |
                ((DPC_BUFFER_SIZE / UNIT - 1) << GUC_LOG_DPC_SHIFT) |
                ((ISR_BUFFER_SIZE / UNIT - 1) << GUC_LOG_ISR_SHIFT) |
                (offset << GUC_LOG_BUF_ADDR_SHIFT);

        #undef UNIT
        #undef FLAG

        return flags;
}

/*
 * Initialise the GuC parameter block before starting the firmware
 * transfer. These parameters are read by the firmware on startup
 * and cannot be changed thereafter.
 */
void intel_guc_init_params(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        u32 params[GUC_CTL_MAX_DWORDS];
        int i;

        memset(params, 0, sizeof(params));

        /*
         * GuC ARAT increment is 10 ns. GuC default scheduler quantum is one
         * second. This ARAR is calculated by:
         * Scheduler-Quantum-in-ns / ARAT-increment-in-ns = 1000000000 / 10
         */
        params[GUC_CTL_ARAT_HIGH] = 0;
        params[GUC_CTL_ARAT_LOW] = 100000000;

        params[GUC_CTL_WA] |= GUC_CTL_WA_UK_BY_DRIVER;

        params[GUC_CTL_FEATURE] = guc_ctl_feature_flags(guc);
        params[GUC_CTL_LOG_PARAMS]  = guc_ctl_log_params_flags(guc);
        params[GUC_CTL_DEBUG] = guc_ctl_debug_flags(guc);
        params[GUC_CTL_CTXINFO] = guc_ctl_ctxinfo_flags(guc);

        for (i = 0; i < GUC_CTL_MAX_DWORDS; i++)
                DRM_DEBUG_DRIVER("param[%2d] = %#x\n", i, params[i]);

        /*
         * All SOFT_SCRATCH registers are in FORCEWAKE_BLITTER domain and
         * they are power context saved so it's ok to release forcewake
         * when we are done here and take it again at xfer time.
         */
        intel_uncore_forcewake_get(dev_priv, FORCEWAKE_BLITTER);

        I915_WRITE(SOFT_SCRATCH(0), 0);

        for (i = 0; i < GUC_CTL_MAX_DWORDS; i++)
                I915_WRITE(SOFT_SCRATCH(1 + i), params[i]);

        intel_uncore_forcewake_put(dev_priv, FORCEWAKE_BLITTER);
}

int intel_guc_send_nop(struct intel_guc *guc, const u32 *action, u32 len,
                       u32 *response_buf, u32 response_buf_size)
{
        WARN(1, "Unexpected send: action=%#x\n", *action);
        return -ENODEV;
}

void intel_guc_to_host_event_handler_nop(struct intel_guc *guc)
{
        WARN(1, "Unexpected event: no suitable handler\n");
}

/*
 * This function implements the MMIO based host to GuC interface.
 */
int intel_guc_send_mmio(struct intel_guc *guc, const u32 *action, u32 len,
                        u32 *response_buf, u32 response_buf_size)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        u32 status;
        int i;
        int ret;

        GEM_BUG_ON(!len);
        GEM_BUG_ON(len > guc->send_regs.count);

        /* We expect only action code */
        GEM_BUG_ON(*action & ~INTEL_GUC_MSG_CODE_MASK);

        /* If CT is available, we expect to use MMIO only during init/fini */
        GEM_BUG_ON(HAS_GUC_CT(dev_priv) &&
                *action != INTEL_GUC_ACTION_REGISTER_COMMAND_TRANSPORT_BUFFER &&
                *action != INTEL_GUC_ACTION_DEREGISTER_COMMAND_TRANSPORT_BUFFER);

        mutex_lock(&guc->send_mutex);
        intel_uncore_forcewake_get(dev_priv, guc->send_regs.fw_domains);

        for (i = 0; i < len; i++)
                I915_WRITE(guc_send_reg(guc, i), action[i]);

        POSTING_READ(guc_send_reg(guc, i - 1));

        intel_guc_notify(guc);

        /*
         * No GuC command should ever take longer than 10ms.
         * Fast commands should still complete in 10us.
         */
        ret = __intel_wait_for_register_fw(dev_priv,
                                           guc_send_reg(guc, 0),
                                           INTEL_GUC_MSG_TYPE_MASK,
                                           INTEL_GUC_MSG_TYPE_RESPONSE <<
                                           INTEL_GUC_MSG_TYPE_SHIFT,
                                           10, 10, &status);
        /* If GuC explicitly returned an error, convert it to -EIO */
        if (!ret && !INTEL_GUC_MSG_IS_RESPONSE_SUCCESS(status))
                ret = -EIO;

        if (ret) {
                DRM_ERROR("MMIO: GuC action %#x failed with error %d %#x\n",
                          action[0], ret, status);
                goto out;
        }

        if (response_buf) {
                int count = min(response_buf_size, guc->send_regs.count - 1);

                for (i = 0; i < count; i++)
                        response_buf[i] = I915_READ(guc_send_reg(guc, i + 1));
        }

        /* Use data from the GuC response as our return value */
        ret = INTEL_GUC_MSG_TO_DATA(status);

out:
        intel_uncore_forcewake_put(dev_priv, guc->send_regs.fw_domains);
        mutex_unlock(&guc->send_mutex);

        return ret;
}

void intel_guc_to_host_event_handler_mmio(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        u32 msg, val;

        /*
         * Sample the log buffer flush related bits & clear them out now
         * itself from the message identity register to minimize the
         * probability of losing a flush interrupt, when there are back
         * to back flush interrupts.
         * There can be a new flush interrupt, for different log buffer
         * type (like for ISR), whilst Host is handling one (for DPC).
         * Since same bit is used in message register for ISR & DPC, it
         * could happen that GuC sets the bit for 2nd interrupt but Host
         * clears out the bit on handling the 1st interrupt.
         */
        disable_rpm_wakeref_asserts(dev_priv);
        spin_lock(&guc->irq_lock);
        val = I915_READ(SOFT_SCRATCH(15));
        msg = val & guc->msg_enabled_mask;
        I915_WRITE(SOFT_SCRATCH(15), val & ~msg);
        spin_unlock(&guc->irq_lock);
        enable_rpm_wakeref_asserts(dev_priv);

        intel_guc_to_host_process_recv_msg(guc, msg);
}

void intel_guc_to_host_process_recv_msg(struct intel_guc *guc, u32 msg)
{
        /* Make sure to handle only enabled messages */
        msg &= guc->msg_enabled_mask;

        if (msg & (INTEL_GUC_RECV_MSG_FLUSH_LOG_BUFFER |
                   INTEL_GUC_RECV_MSG_CRASH_DUMP_POSTED))
                intel_guc_log_handle_flush_event(&guc->log);
}

int intel_guc_sample_forcewake(struct intel_guc *guc)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        u32 action[2];

        action[0] = INTEL_GUC_ACTION_SAMPLE_FORCEWAKE;
        /* WaRsDisableCoarsePowerGating:skl,cnl */
        if (!HAS_RC6(dev_priv) || NEEDS_WaRsDisableCoarsePowerGating(dev_priv))
                action[1] = 0;
        else
                /* bit 0 and 1 are for Render and Media domain separately */
                action[1] = GUC_FORCEWAKE_RENDER | GUC_FORCEWAKE_MEDIA;

        return intel_guc_send(guc, action, ARRAY_SIZE(action));
}

/**
 * intel_guc_auth_huc() - Send action to GuC to authenticate HuC ucode
 * @guc: intel_guc structure
 * @rsa_offset: rsa offset w.r.t ggtt base of huc vma
 *
 * Triggers a HuC firmware authentication request to the GuC via intel_guc_send
 * INTEL_GUC_ACTION_AUTHENTICATE_HUC interface. This function is invoked by
 * intel_huc_auth().
 *
 * Return:      non-zero code on error
 */
int intel_guc_auth_huc(struct intel_guc *guc, u32 rsa_offset)
{
        u32 action[] = {
                INTEL_GUC_ACTION_AUTHENTICATE_HUC,
                rsa_offset
        };

        return intel_guc_send(guc, action, ARRAY_SIZE(action));
}

/**
 * intel_guc_suspend() - notify GuC entering suspend state
 * @guc:        the guc
 */
int intel_guc_suspend(struct intel_guc *guc)
{
        u32 data[] = {
                INTEL_GUC_ACTION_ENTER_S_STATE,
                GUC_POWER_D1, /* any value greater than GUC_POWER_D0 */
                intel_guc_ggtt_offset(guc, guc->shared_data)
        };

        return intel_guc_send(guc, data, ARRAY_SIZE(data));
}

/**
 * intel_guc_reset_engine() - ask GuC to reset an engine
 * @guc:        intel_guc structure
 * @engine:     engine to be reset
 */
int intel_guc_reset_engine(struct intel_guc *guc,
                           struct intel_engine_cs *engine)
{
        u32 data[7];

        GEM_BUG_ON(!guc->execbuf_client);

        data[0] = INTEL_GUC_ACTION_REQUEST_ENGINE_RESET;
        data[1] = engine->guc_id;
        data[2] = 0;
        data[3] = 0;
        data[4] = 0;
        data[5] = guc->execbuf_client->stage_id;
        data[6] = intel_guc_ggtt_offset(guc, guc->shared_data);

        return intel_guc_send(guc, data, ARRAY_SIZE(data));
}

/**
 * intel_guc_resume() - notify GuC resuming from suspend state
 * @guc:        the guc
 */
int intel_guc_resume(struct intel_guc *guc)
{
        u32 data[] = {
                INTEL_GUC_ACTION_EXIT_S_STATE,
                GUC_POWER_D0,
                intel_guc_ggtt_offset(guc, guc->shared_data)
        };

        return intel_guc_send(guc, data, ARRAY_SIZE(data));
}

/**
 * DOC: GuC Address Space
 *
 * The layout of GuC address space is shown below:
 *
 * ::
 *
 *     +==============> +====================+ <== GUC_GGTT_TOP
 *     ^                |                    |
 *     |                |                    |
 *     |                |        DRAM        |
 *     |                |       Memory       |
 *     |                |                    |
 *    GuC               |                    |
 *  Address  +========> +====================+ <== WOPCM Top
 *   Space   ^          |   HW contexts RSVD |
 *     |     |          |        WOPCM       |
 *     |     |     +==> +--------------------+ <== GuC WOPCM Top
 *     |    GuC    ^    |                    |
 *     |    GGTT   |    |                    |
 *     |    Pin   GuC   |        GuC         |
 *     |    Bias WOPCM  |       WOPCM        |
 *     |     |    Size  |                    |
 *     |     |     |    |                    |
 *     v     v     v    |                    |
 *     +=====+=====+==> +====================+ <== GuC WOPCM Base
 *                      |   Non-GuC WOPCM    |
 *                      |   (HuC/Reserved)   |
 *                      +====================+ <== WOPCM Base
 *
 * The lower part of GuC Address Space [0, ggtt_pin_bias) is mapped to WOPCM
 * while upper part of GuC Address Space [ggtt_pin_bias, GUC_GGTT_TOP) is mapped
 * to DRAM. The value of the GuC ggtt_pin_bias is determined by WOPCM size and
 * actual GuC WOPCM size.
 */

/**
 * guc_init_ggtt_pin_bias() - Initialize the GuC ggtt_pin_bias value.
 * @guc: intel_guc structure.
 *
 * This function will calculate and initialize the ggtt_pin_bias value based on
 * overall WOPCM size and GuC WOPCM size.
 */
static void guc_init_ggtt_pin_bias(struct intel_guc *guc)
{
        struct drm_i915_private *i915 = guc_to_i915(guc);

        GEM_BUG_ON(!i915->wopcm.size);
        GEM_BUG_ON(i915->wopcm.size < i915->wopcm.guc.base);

        guc->ggtt_pin_bias = i915->wopcm.size - i915->wopcm.guc.base;
}

/**
 * intel_guc_allocate_vma() - Allocate a GGTT VMA for GuC usage
 * @guc:        the guc
 * @size:       size of area to allocate (both virtual space and memory)
 *
 * This is a wrapper to create an object for use with the GuC. In order to
 * use it inside the GuC, an object needs to be pinned lifetime, so we allocate
 * both some backing storage and a range inside the Global GTT. We must pin
 * it in the GGTT somewhere other than than [0, GUC ggtt_pin_bias) because that
 * range is reserved inside GuC.
 *
 * Return:      A i915_vma if successful, otherwise an ERR_PTR.
 */
struct i915_vma *intel_guc_allocate_vma(struct intel_guc *guc, u32 size)
{
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        struct drm_i915_gem_object *obj;
        struct i915_vma *vma;
        int ret;

        obj = i915_gem_object_create(dev_priv, size);
        if (IS_ERR(obj))
                return ERR_CAST(obj);

        vma = i915_vma_instance(obj, &dev_priv->ggtt.vm, NULL);
        if (IS_ERR(vma))
                goto err;

        ret = i915_vma_pin(vma, 0, PAGE_SIZE,
                           PIN_GLOBAL | PIN_OFFSET_BIAS | guc->ggtt_pin_bias);
        if (ret) {
                vma = ERR_PTR(ret);
                goto err;
        }

        return vma;

err:
        i915_gem_object_put(obj);
        return vma;
}