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drm/xe/mmio_gem: cache the dummy page per object

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Currently, when the fault handler provides a dummy page, it
allocates a new one on every invocation and ties its lifetime to
the drm_device via drmm_add_action_or_reset(). Concurrent faults
after hot-unplug therefore accumulate pages that persist until
device teardown.

Cache a single dummy page in the xe_mmio_gem object and use dma_resv
lock to protect its allocation. Free it with the object.

v2: use dma_resv lock to protect the allocation (Matt Auld)

Assisted-by: GitHub-Copilot:claude-opus-4.6
Signed-off-by: Ilia Levi <ilia.levi@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patch.msgid.link/20260908165046.1393557-15-matthew.auld@intel.com
(cherry picked from commit 8bf6213f9831e46313af4722a1ee6db1b7596378)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
This commit is contained in:
Ilia Levi 2026-09-08 17:50:52 +01:00 committed by Rodrigo Vivi
parent 37fcbd7b2f
commit de40d31275
No known key found for this signature in database
GPG Key ID: FA625F640EEB13CA
1 changed files with 16 additions and 11 deletions
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27
drivers/gpu/drm/xe/xe_mmio_gem.c
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@ -5,9 +5,9 @@
#include "xe_mmio_gem.h"
#include <linux/dma-resv.h>
#include <drm/drm_drv.h>
#include <drm/drm_gem.h>
#include <drm/drm_managed.h>
#include "xe_device_types.h"
@ -37,6 +37,7 @@ static vm_fault_t xe_mmio_gem_vm_fault(struct vm_fault *);
struct xe_mmio_gem {
struct drm_gem_object base;
phys_addr_t phys_addr;
struct page *dummy_page; /* protected by the GEM's dma_resv */
};
static int xe_mmio_gem_vm_may_split(struct vm_area_struct *area, unsigned long addr)
@ -131,6 +132,8 @@ static void xe_mmio_gem_free(struct drm_gem_object *base)
{
struct xe_mmio_gem *obj = to_xe_mmio_gem(base);
if (obj->dummy_page)
__free_page(obj->dummy_page);
drm_gem_object_release(base);
kfree(obj);
}
@ -169,27 +172,29 @@ static int xe_mmio_gem_mmap(struct drm_gem_object *base, struct vm_area_struct *
return 0;
}
static void xe_mmio_gem_release_dummy_page(struct drm_device *dev, void *res)
static int alloc_dummy_page_if_needed(struct drm_gem_object *base)
{
__free_page((struct page *)res);
struct xe_mmio_gem *obj = to_xe_mmio_gem(base);
dma_resv_lock(base->resv, NULL);
if (!obj->dummy_page)
obj->dummy_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
dma_resv_unlock(base->resv);
return obj->dummy_page ? 0 : -ENOMEM;
}
static vm_fault_t xe_mmio_gem_vm_fault_dummy_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct drm_gem_object *base = vma->vm_private_data;
struct drm_device *dev = base->dev;
struct page *page;
struct xe_mmio_gem *obj = to_xe_mmio_gem(base);
unsigned long pfn;
page = alloc_page(GFP_KERNEL | __GFP_ZERO);
if (!page)
if (alloc_dummy_page_if_needed(base))
return VM_FAULT_OOM;
if (drmm_add_action_or_reset(dev, xe_mmio_gem_release_dummy_page, page))
return VM_FAULT_OOM;
pfn = page_to_pfn(page);
pfn = page_to_pfn(obj->dummy_page);
return vmf_insert_pfn_prot(vma, vmf->address, pfn,
vm_get_page_prot(vma->vm_flags));