Re: [PATCH 2/6] drm/i915: Add second slice l3 remapping

Ville Syrjälä
2013-09-18T07:36:36Z

On Tue, Sep 17, 2013 at 09:12:43PM -0700, Ben Widawsky wrote:
> Certain HSW SKUs have a second bank of L3. This L3 remapping has a
> separate register set, and interrupt from the first "slice". A slice is
> simply a term to define some subset of the GPU's l3 cache. This patch
> implements both the interrupt handler, and ability to communicate with
> userspace about this second slice.
>
> v2: Remove redundant check about non-existent slice.
> Change warning about interrupts of unknown slices to WARN_ON_ONCE
> Handle the case where we get 2 slice interrupts concurrently, and switch
> the tracking of interrupts to be non-destructive (all Ville)
> Don't enable/mask the second slice parity interrupt for ivb/vlv (even
> though all docs I can find claim it's rsvd) (Ville + Bryan)
> Keep BYT excluded from L3 parity
>
> CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 7 ++-
> drivers/gpu/drm/i915/i915_gem.c | 26 +++++-----
> drivers/gpu/drm/i915/i915_irq.c | 88 +++++++++++++++++++++------------
> drivers/gpu/drm/i915/i915_reg.h | 7 +++
> drivers/gpu/drm/i915/i915_sysfs.c | 34 ++++++++++---
> drivers/gpu/drm/i915/intel_ringbuffer.c | 7 ++-
> include/uapi/drm/i915_drm.h | 8 +--
> 7 files changed, 116 insertions(+), 61 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 8b16d47..c6e8df7 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -917,9 +917,11 @@ struct i915_ums_state {
> int mm_suspended;
> };
>
> +#define MAX_L3_SLICES 2
> struct intel_l3_parity {
> - u32 *remap_info;
> + u32 *remap_info[MAX_L3_SLICES];
> struct work_struct error_work;
> + int which_slice;
> };
>
> struct i915_gem_mm {
> @@ -1686,6 +1688,7 @@ struct drm_i915_file_private {
> #define HAS_FORCE_WAKE(dev) (INTEL_INFO(dev)->has_force_wake)
>
> #define HAS_L3_GPU_CACHE(dev) (IS_IVYBRIDGE(dev) || IS_HASWELL(dev))
> +#define NUM_L3_SLICES(dev) (IS_HSW_GT3(dev) ? 2 : HAS_L3_GPU_CACHE(dev))
>
> #define GT_FREQUENCY_MULTIPLIER 50
>
> @@ -1946,7 +1949,7 @@ bool i915_gem_clflush_object(struct drm_i915_gem_object *obj, bool force);
> int __must_check i915_gem_object_finish_gpu(struct drm_i915_gem_object *obj);
> int __must_check i915_gem_init(struct drm_device *dev);
> int __must_check i915_gem_init_hw(struct drm_device *dev);
> -void i915_gem_l3_remap(struct drm_device *dev);
> +void i915_gem_l3_remap(struct drm_device *dev, int slice);
> void i915_gem_init_swizzling(struct drm_device *dev);
> void i915_gem_cleanup_ringbuffer(struct drm_device *dev);
> int __must_check i915_gpu_idle(struct drm_device *dev);
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 3d3de6e..66bf75d 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -4252,16 +4252,15 @@ i915_gem_idle(struct drm_device *dev)
> return 0;
> }
>
> -void i915_gem_l3_remap(struct drm_device *dev)
> +void i915_gem_l3_remap(struct drm_device *dev, int slice)
> {
> drm_i915_private_t *dev_priv = dev->dev_private;
> + u32 reg_base = GEN7_L3LOG_BASE + (slice * 0x200);
> + u32 *remap_info = dev_priv->l3_parity.remap_info[slice];
> u32 misccpctl;
> int i;
>
> - if (!HAS_L3_GPU_CACHE(dev))
> - return;
> -
> - if (!dev_priv->l3_parity.remap_info)
> + if (!HAS_L3_GPU_CACHE(dev) || !remap_info)
> return;
>
> misccpctl = I915_READ(GEN7_MISCCPCTL);
> @@ -4269,17 +4268,17 @@ void i915_gem_l3_remap(struct drm_device *dev)
> POSTING_READ(GEN7_MISCCPCTL);
>
> for (i = 0; i < GEN7_L3LOG_SIZE; i += 4) {
> - u32 remap = I915_READ(GEN7_L3LOG_BASE + i);
> - if (remap && remap != dev_priv->l3_parity.remap_info[i/4])
> + u32 remap = I915_READ(reg_base + i);
> + if (remap && remap != remap_info[i/4])
> DRM_DEBUG("0x%x was already programmed to %x\n",
> - GEN7_L3LOG_BASE + i, remap);
> - if (remap && !dev_priv->l3_parity.remap_info[i/4])
> + reg_base + i, remap);
> + if (remap && !remap_info[i/4])
> DRM_DEBUG_DRIVER("Clearing remapped register\n");
> - I915_WRITE(GEN7_L3LOG_BASE + i, dev_priv->l3_parity.remap_info[i/4]);
> + I915_WRITE(reg_base + i, remap_info[i/4]);
> }
>
> /* Make sure all the writes land before disabling dop clock gating */
> - POSTING_READ(GEN7_L3LOG_BASE);
> + POSTING_READ(reg_base);
>
> I915_WRITE(GEN7_MISCCPCTL, misccpctl);
> }
> @@ -4373,7 +4372,7 @@ int
> i915_gem_init_hw(struct drm_device *dev)
> {
> drm_i915_private_t *dev_priv = dev->dev_private;
> - int ret;
> + int ret, i;
>
> if (INTEL_INFO(dev)->gen < 6 && !intel_enable_gtt())
> return -EIO;
> @@ -4392,7 +4391,8 @@ i915_gem_init_hw(struct drm_device *dev)
> I915_WRITE(GEN7_MSG_CTL, temp);
> }
>
> - i915_gem_l3_remap(dev);
> + for (i = 0; i < NUM_L3_SLICES(dev); i++)
> + i915_gem_l3_remap(dev, i);
>
> i915_gem_init_swizzling(dev);
>
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index a42f30b..b11ee39 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -888,9 +888,10 @@ static void ivybridge_parity_work(struct work_struct *work)
> drm_i915_private_t *dev_priv = container_of(work, drm_i915_private_t,
> l3_parity.error_work);
> u32 error_status, row, bank, subbank;
> - char *parity_event[5];
> + char *parity_event[6];
> uint32_t misccpctl;
> unsigned long flags;
> + uint8_t slice = 0;
>
> /* We must turn off DOP level clock gating to access the L3 registers.
> * In order to prevent a get/put style interface, acquire struct mutex
> @@ -898,45 +899,63 @@ static void ivybridge_parity_work(struct work_struct *work)
> */
> mutex_lock(&dev_priv->dev->struct_mutex);
>
> + /* If we've screwed up tracking, just let the interrupt fire again */
> + if (WARN_ON(!dev_priv->l3_parity.which_slice))
> + goto out;
> +
> misccpctl = I915_READ(GEN7_MISCCPCTL);
> I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
> POSTING_READ(GEN7_MISCCPCTL);
>
> - error_status = I915_READ(GEN7_L3CDERRST1);
> - row = GEN7_PARITY_ERROR_ROW(error_status);
> - bank = GEN7_PARITY_ERROR_BANK(error_status);
> - subbank = GEN7_PARITY_ERROR_SUBBANK(error_status);
> + while ((slice = ffs(dev_priv->l3_parity.which_slice)) != 0) {
> + u32 reg;

ffs(1) == 1, so we need a slice-- here, don't we?

The rest looks OK to me, so once this one thing is fixed you can slap on a
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
sticker.

>
> - I915_WRITE(GEN7_L3CDERRST1, GEN7_PARITY_ERROR_VALID |
> - GEN7_L3CDERRST1_ENABLE);
> - POSTING_READ(GEN7_L3CDERRST1);
> + if (WARN_ON_ONCE(slice >= NUM_L3_SLICES(dev_priv->dev)))
> + break;
>
> - I915_WRITE(GEN7_MISCCPCTL, misccpctl);
> + dev_priv->l3_parity.which_slice &= ~(1<<slice);
>
> - spin_lock_irqsave(&dev_priv->irq_lock, flags);
> - ilk_enable_gt_irq(dev_priv, GT_RENDER_L3_PARITY_ERROR_INTERRUPT);
> - spin_unlock_irqrestore(&dev_priv->irq_lock, flags);
> + reg = GEN7_L3CDERRST1 + (slice * 0x200);
>
> - mutex_unlock(&dev_priv->dev->struct_mutex);
> + error_status = I915_READ(reg);
> + row = GEN7_PARITY_ERROR_ROW(error_status);
> + bank = GEN7_PARITY_ERROR_BANK(error_status);
> + subbank = GEN7_PARITY_ERROR_SUBBANK(error_status);
> +
> + I915_WRITE(reg, GEN7_PARITY_ERROR_VALID | GEN7_L3CDERRST1_ENABLE);
> + POSTING_READ(reg);
> +
> + parity_event[0] = I915_L3_PARITY_UEVENT "=1";
> + parity_event[1] = kasprintf(GFP_KERNEL, "ROW=%d", row);
> + parity_event[2] = kasprintf(GFP_KERNEL, "BANK=%d", bank);
> + parity_event[3] = kasprintf(GFP_KERNEL, "SUBBANK=%d", subbank);
> + parity_event[4] = kasprintf(GFP_KERNEL, "SLICE=%d", slice);
> + parity_event[5] = NULL;
> +
> + kobject_uevent_env(&dev_priv->dev->primary->kdev.kobj,
> + KOBJ_CHANGE, parity_event);
>
> - parity_event[0] = I915_L3_PARITY_UEVENT "=1";
> - parity_event[1] = kasprintf(GFP_KERNEL, "ROW=%d", row);
> - parity_event[2] = kasprintf(GFP_KERNEL, "BANK=%d", bank);
> - parity_event[3] = kasprintf(GFP_KERNEL, "SUBBANK=%d", subbank);
> - parity_event[4] = NULL;
> + DRM_DEBUG("Parity error: Slice = %d, Row = %d, Bank = %d, Sub bank = %d.\n",
> + slice, row, bank, subbank);
>
> - kobject_uevent_env(&dev_priv->dev->primary->kdev.kobj,
> - KOBJ_CHANGE, parity_event);
> + kfree(parity_event[4]);
> + kfree(parity_event[3]);
> + kfree(parity_event[2]);
> + kfree(parity_event[1]);
> + }
>
> - DRM_DEBUG("Parity error: Row = %d, Bank = %d, Sub bank = %d.\n",
> - row, bank, subbank);
> + I915_WRITE(GEN7_MISCCPCTL, misccpctl);
>
> - kfree(parity_event[3]);
> - kfree(parity_event[2]);
> - kfree(parity_event[1]);
> +out:
> + WARN_ON(dev_priv->l3_parity.which_slice);
> + spin_lock_irqsave(&dev_priv->irq_lock, flags);
> + ilk_enable_gt_irq(dev_priv, GT_PARITY_ERROR(dev_priv->dev));
> + spin_unlock_irqrestore(&dev_priv->irq_lock, flags);
> +
> + mutex_unlock(&dev_priv->dev->struct_mutex);
> }
>
> -static void ivybridge_parity_error_irq_handler(struct drm_device *dev)
> +static void ivybridge_parity_error_irq_handler(struct drm_device *dev, u32 iir)
> {
> drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
>
> @@ -944,9 +963,16 @@ static void ivybridge_parity_error_irq_handler(struct drm_device *dev)
> return;
>
> spin_lock(&dev_priv->irq_lock);
> - ilk_disable_gt_irq(dev_priv, GT_RENDER_L3_PARITY_ERROR_INTERRUPT);
> + ilk_disable_gt_irq(dev_priv, GT_PARITY_ERROR(dev));
> spin_unlock(&dev_priv->irq_lock);
>
> + iir &= GT_PARITY_ERROR(dev);
> + if (iir & GT_RENDER_L3_PARITY_ERROR_INTERRUPT_S1)
> + dev_priv->l3_parity.which_slice |= 1 << 1;
> +
> + if (iir & GT_RENDER_L3_PARITY_ERROR_INTERRUPT)
> + dev_priv->l3_parity.which_slice |= 1 << 0;
> +
> queue_work(dev_priv->wq, &dev_priv->l3_parity.error_work);
> }
>
> @@ -981,8 +1007,8 @@ static void snb_gt_irq_handler(struct drm_device *dev,
> i915_handle_error(dev, false);
> }
>
> - if (gt_iir & GT_RENDER_L3_PARITY_ERROR_INTERRUPT)
> - ivybridge_parity_error_irq_handler(dev);
> + if (gt_iir & GT_PARITY_ERROR(dev))
> + ivybridge_parity_error_irq_handler(dev, gt_iir);
> }
>
> #define HPD_STORM_DETECT_PERIOD 1000
> @@ -2267,8 +2293,8 @@ static void gen5_gt_irq_postinstall(struct drm_device *dev)
> dev_priv->gt_irq_mask = ~0;
> if (HAS_L3_GPU_CACHE(dev)) {
> /* L3 parity interrupt is always unmasked. */
> - dev_priv->gt_irq_mask = ~GT_RENDER_L3_PARITY_ERROR_INTERRUPT;
> - gt_irqs |= GT_RENDER_L3_PARITY_ERROR_INTERRUPT;
> + dev_priv->gt_irq_mask = ~GT_PARITY_ERROR(dev);
> + gt_irqs |= GT_PARITY_ERROR(dev);
> }
>
> gt_irqs |= GT_RENDER_USER_INTERRUPT;
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 384adfb..c94946f 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -927,6 +927,7 @@
> #define GT_BLT_USER_INTERRUPT (1 << 22)
> #define GT_BSD_CS_ERROR_INTERRUPT (1 << 15)
> #define GT_BSD_USER_INTERRUPT (1 << 12)
> +#define GT_RENDER_L3_PARITY_ERROR_INTERRUPT_S1 (1 << 11) /* hsw+; rsvd on snb, ivb, vlv */
> #define GT_RENDER_L3_PARITY_ERROR_INTERRUPT (1 << 5) /* !snb */
> #define GT_RENDER_PIPECTL_NOTIFY_INTERRUPT (1 << 4)
> #define GT_RENDER_CS_MASTER_ERROR_INTERRUPT (1 << 3)
> @@ -937,6 +938,10 @@
> #define PM_VEBOX_CS_ERROR_INTERRUPT (1 << 12) /* hsw+ */
> #define PM_VEBOX_USER_INTERRUPT (1 << 10) /* hsw+ */
>
> +#define GT_PARITY_ERROR(dev) \
> + (GT_RENDER_L3_PARITY_ERROR_INTERRUPT | \
> + IS_HASWELL(dev) ? GT_RENDER_L3_PARITY_ERROR_INTERRUPT_S1 : 0)
> +
> /* These are all the "old" interrupts */
> #define ILK_BSD_USER_INTERRUPT (1<<5)
> #define I915_PIPE_CONTROL_NOTIFY_INTERRUPT (1<<18)
> @@ -4743,6 +4748,7 @@
>
> /* IVYBRIDGE DPF */
> #define GEN7_L3CDERRST1 0xB008 /* L3CD Error Status 1 */
> +#define HSW_L3CDERRST11 0xB208 /* L3CD Error Status register 1 slice 1 */
> #define GEN7_L3CDERRST1_ROW_MASK (0x7ff<<14)
> #define GEN7_PARITY_ERROR_VALID (1<<13)
> #define GEN7_L3CDERRST1_BANK_MASK (3<<11)
> @@ -4756,6 +4762,7 @@
> #define GEN7_L3CDERRST1_ENABLE (1<<7)
>
> #define GEN7_L3LOG_BASE 0xB070
> +#define HSW_L3LOG_BASE_SLICE1 0xB270
> #define GEN7_L3LOG_SIZE 0x80
>
> #define GEN7_HALF_SLICE_CHICKEN1 0xe100 /* IVB GT1 + VLV */
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index 71f6de2..3a8bf0c 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -119,6 +119,7 @@ i915_l3_read(struct file *filp, struct kobject *kobj,
> struct drm_device *drm_dev = dminor->dev;
> struct drm_i915_private *dev_priv = drm_dev->dev_private;
> uint32_t misccpctl;
> + int slice = (int)(uintptr_t)attr->private;
> int i, ret;
>
> count = round_down(count, 4);
> @@ -134,9 +135,9 @@ i915_l3_read(struct file *filp, struct kobject *kobj,
> return ret;
>
> if (IS_HASWELL(drm_dev)) {
> - if (dev_priv->l3_parity.remap_info)
> + if (dev_priv->l3_parity.remap_info[slice])
> memcpy(buf,
> - dev_priv->l3_parity.remap_info + (offset/4),
> + dev_priv->l3_parity.remap_info[slice] + (offset/4),
> count);
> else
> memset(buf, 0, count);
> @@ -168,6 +169,7 @@ i915_l3_write(struct file *filp, struct kobject *kobj,
> struct drm_device *drm_dev = dminor->dev;
> struct drm_i915_private *dev_priv = drm_dev->dev_private;
> u32 *temp = NULL; /* Just here to make handling failures easy */
> + int slice = (int)(uintptr_t)attr->private;
> int ret;
>
> ret = l3_access_valid(drm_dev, offset);
> @@ -178,7 +180,7 @@ i915_l3_write(struct file *filp, struct kobject *kobj,
> if (ret)
> return ret;
>
> - if (!dev_priv->l3_parity.remap_info) {
> + if (!dev_priv->l3_parity.remap_info[slice]) {
> temp = kzalloc(GEN7_L3LOG_SIZE, GFP_KERNEL);
> if (!temp) {
> mutex_unlock(&drm_dev->struct_mutex);
> @@ -198,11 +200,11 @@ i915_l3_write(struct file *filp, struct kobject *kobj,
> * at this point it is left as a TODO.
> */
> if (temp)
> - dev_priv->l3_parity.remap_info = temp;
> + dev_priv->l3_parity.remap_info[slice] = temp;
>
> - memcpy(dev_priv->l3_parity.remap_info + (offset/4), buf, count);
> + memcpy(dev_priv->l3_parity.remap_info[slice] + (offset/4), buf, count);
>
> - i915_gem_l3_remap(drm_dev);
> + i915_gem_l3_remap(drm_dev, slice);
>
> mutex_unlock(&drm_dev->struct_mutex);
>
> @@ -214,7 +216,17 @@ static struct bin_attribute dpf_attrs = {
> .size = GEN7_L3LOG_SIZE,
> .read = i915_l3_read,
> .write = i915_l3_write,
> - .mmap = NULL
> + .mmap = NULL,
> + .private = (void *)0
> +};
> +
> +static struct bin_attribute dpf_attrs_1 = {
> + .attr = {.name = "l3_parity_slice_1", .mode = (S_IRUSR | S_IWUSR)},
> + .size = GEN7_L3LOG_SIZE,
> + .read = i915_l3_read,
> + .write = i915_l3_write,
> + .mmap = NULL,
> + .private = (void *)1
> };
>
> static ssize_t gt_cur_freq_mhz_show(struct device *kdev,
> @@ -525,6 +537,13 @@ void i915_setup_sysfs(struct drm_device *dev)
> ret = device_create_bin_file(&dev->primary->kdev, &dpf_attrs);
> if (ret)
> DRM_ERROR("l3 parity sysfs setup failed\n");
> +
> + if (NUM_L3_SLICES(dev) > 1) {
> + ret = device_create_bin_file(&dev->primary->kdev,
> + &dpf_attrs_1);
> + if (ret)
> + DRM_ERROR("l3 parity slice 1 setup failed\n");
> + }
> }
>
> ret = 0;
> @@ -548,6 +567,7 @@ void i915_teardown_sysfs(struct drm_device *dev)
> sysfs_remove_files(&dev->primary->kdev.kobj, vlv_attrs);
> else
> sysfs_remove_files(&dev->primary->kdev.kobj, gen6_attrs);
> + device_remove_bin_file(&dev->primary->kdev, &dpf_attrs_1);
> device_remove_bin_file(&dev->primary->kdev, &dpf_attrs);
> #ifdef CONFIG_PM
> sysfs_unmerge_group(&dev->primary->kdev.kobj, &rc6_attr_group);
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 686e5b2..958b7d8 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -570,7 +570,7 @@ static int init_render_ring(struct intel_ring_buffer *ring)
> I915_WRITE(INSTPM, _MASKED_BIT_ENABLE(INSTPM_FORCE_ORDERING));
>
> if (HAS_L3_GPU_CACHE(dev))
> - I915_WRITE_IMR(ring, ~GT_RENDER_L3_PARITY_ERROR_INTERRUPT);
> + I915_WRITE_IMR(ring, ~GT_PARITY_ERROR(dev));
>
> return ret;
> }
> @@ -1000,7 +1000,7 @@ gen6_ring_get_irq(struct intel_ring_buffer *ring)
> if (HAS_L3_GPU_CACHE(dev) && ring->id == RCS)
> I915_WRITE_IMR(ring,
> ~(ring->irq_enable_mask |
> - GT_RENDER_L3_PARITY_ERROR_INTERRUPT));
> + GT_PARITY_ERROR(dev)));
> else
> I915_WRITE_IMR(ring, ~ring->irq_enable_mask);
> ilk_enable_gt_irq(dev_priv, ring->irq_enable_mask);
> @@ -1020,8 +1020,7 @@ gen6_ring_put_irq(struct intel_ring_buffer *ring)
> spin_lock_irqsave(&dev_priv->irq_lock, flags);
> if (--ring->irq_refcount == 0) {
> if (HAS_L3_GPU_CACHE(dev) && ring->id == RCS)
> - I915_WRITE_IMR(ring,
> - ~GT_RENDER_L3_PARITY_ERROR_INTERRUPT);
> + I915_WRITE_IMR(ring, ~GT_PARITY_ERROR(dev));
> else
> I915_WRITE_IMR(ring, ~0);
> ilk_disable_gt_irq(dev_priv, ring->irq_enable_mask);
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 55bb572..3a4e97b 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -38,10 +38,10 @@
> *
> * I915_L3_PARITY_UEVENT - Generated when the driver receives a parity mismatch
> * event from the gpu l3 cache. Additional information supplied is ROW,
> - * BANK, SUBBANK of the affected cacheline. Userspace should keep track of
> - * these events and if a specific cache-line seems to have a persistent
> - * error remap it with the l3 remapping tool supplied in intel-gpu-tools.
> - * The value supplied with the event is always 1.
> + * BANK, SUBBANK, SLICE of the affected cacheline. Userspace should keep
> + * track of these events and if a specific cache-line seems to have a
> + * persistent error remap it with the l3 remapping tool supplied in
> + * intel-gpu-tools. The value supplied with the event is always 1.
> *
> * I915_ERROR_UEVENT - Generated upon error detection, currently only via
> * hangcheck. The error detection event is a good indicator of when things
> --
> 1.8.4

--
Ville Syrjälä
Intel OTC