On 6/29/26 02:50, James Zhu wrote: > After moving TBA/TMA from GTT to VRAM for GFX9.4.2+ in commit > 5088a1ba6d6d, direct pointer dereferences to CWSR buffers became > unsafe because VRAM is accessed via MMIO (PCI BAR mappings). > > Direct writes like 'tma[2] = enabled' and memcpy() can fail or > produce incorrect results on non-x86 architectures because: > - MMIO requires specific accessor functions (writeq/readq) > - Compiler optimizations may generate invalid instruction sequences > - No guarantee of proper memory barriers or atomic access > > This patch converts CWSR buffer access to use struct iosys_map, > which automatically handles both system memory (GTT) and MMIO > (VRAM) correctly by: > - Using writeq/writel/memcpy_toio for MMIO regions > - Using WRITE_ONCE/memcpy for system memory > - Providing proper memory barriers and access guarantees > > Changes: > - Replace void *cwsr_kaddr with struct iosys_map cwsr_map > - Detect MMIO vs system memory using TTM_BO_MAP_IOMEM_MASK > - Use iosys_map_wr() for writing trap handler addresses and flags > - Use iosys_map_memcpy_to() for copying CWSR ISA code > > This ensures correct operation on all architectures while maintaining > backward compatibility with older GPUs and APUs that use GTT. > > Co-Authored-By: Claude Opus 4.6 <[email protected]> > Co-Authored-By: Yifan Zhang <[email protected]> > Signed-off-by: James Zhu <[email protected]>
Looks valid of hand, but I have no time for an in deep review. Somebody who knows the code should take another look as well. But feel free to add Acked-by: Christian König <[email protected]>. Regards, Christian. > --- > drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 3 +- > drivers/gpu/drm/amd/amdkfd/kfd_process.c | 63 +++++++++++++++++------- > 2 files changed, 47 insertions(+), 19 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h > b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h > index ad4897f094a2..6e559aab4009 100644 > --- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h > @@ -32,6 +32,7 @@ > #include <linux/atomic.h> > #include <linux/workqueue.h> > #include <linux/spinlock.h> > +#include <linux/iosys-map.h> > #include <uapi/linux/kfd_ioctl.h> > #include <linux/idr.h> > #include <linux/kfifo.h> > @@ -710,7 +711,7 @@ struct qcm_process_device { > > /* CWSR memory */ > struct kgd_mem *cwsr_mem; > - void *cwsr_kaddr; > + struct iosys_map cwsr_map; > uint64_t cwsr_base; > uint64_t tba_addr; > uint64_t tma_addr; > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c > b/drivers/gpu/drm/amd/amdkfd/kfd_process.c > index 8e701dcda8ec..7fd65c31afa2 100644 > --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c > @@ -33,6 +33,7 @@ > #include <linux/mman.h> > #include <linux/file.h> > #include <linux/pm_runtime.h> > +#include <drm/ttm/ttm_bo.h> > #include "amdgpu_amdkfd.h" > #include "amdgpu.h" > #include "amdgpu_reset.h" > @@ -745,6 +746,21 @@ static void kfd_process_free_gpuvm(struct kgd_mem *mem, > NULL); > } > > +static void kfd_process_free_gpuvm_map(struct kgd_mem *mem, > + struct kfd_process_device *pdd, struct iosys_map *map) > +{ > + struct kfd_node *dev = pdd->dev; > + > + if (map && !iosys_map_is_null(map)) { > + amdgpu_amdkfd_gpuvm_unmap_bo_from_kernel(mem); > + iosys_map_clear(map); > + } > + > + amdgpu_amdkfd_gpuvm_unmap_memory_from_gpu(dev->adev, mem, > pdd->drm_priv); > + amdgpu_amdkfd_gpuvm_free_memory_of_gpu(dev->adev, mem, pdd->drm_priv, > + NULL); > +} > + > /* kfd_process_alloc_gpuvm - Allocate GPU VM for the KFD process > * This function should be only called right after the process > * is created and when kfd_processes_mutex is still being held > @@ -1192,8 +1208,8 @@ static void kfd_process_destroy_pdds(struct kfd_process > *p) > if (pdd->drm_file) > fput(pdd->drm_file); > > - if (pdd->qpd.cwsr_kaddr && !pdd->qpd.cwsr_base) > - free_pages((unsigned long)pdd->qpd.cwsr_kaddr, > + if (!iosys_map_is_null(&pdd->qpd.cwsr_map) && > !pdd->qpd.cwsr_base) > + free_pages((unsigned long)pdd->qpd.cwsr_map.vaddr, > get_order(KFD_CWSR_TBA_TMA_SIZE)); > > idr_destroy(&pdd->alloc_idr); > @@ -1501,7 +1517,7 @@ static int kfd_process_device_init_cwsr_dgpu(struct > kfd_process_device *pdd) > void *kaddr; > int ret; > > - if (!dev->kfd->cwsr_enabled || qpd->cwsr_kaddr || !qpd->cwsr_base) > + if (!dev->kfd->cwsr_enabled || !iosys_map_is_null(&qpd->cwsr_map) || > !qpd->cwsr_base) > return 0; > > if (KFD_GC_VERSION(dev) >= IP_VERSION(9, 4, 2) && > !dev->adev->apu_prefer_gtt) > @@ -1516,17 +1532,28 @@ static int kfd_process_device_init_cwsr_dgpu(struct > kfd_process_device *pdd) > return ret; > > qpd->cwsr_mem = mem; > - qpd->cwsr_kaddr = kaddr; > + > + /* Set up iosys_map based on whether memory is MMIO or system memory */ > + if (mem->bo->kmap.bo_kmap_type & TTM_BO_MAP_IOMEM_MASK) > + iosys_map_set_vaddr_iomem(&qpd->cwsr_map, kaddr); > + else > + iosys_map_set_vaddr(&qpd->cwsr_map, kaddr); > + > qpd->tba_addr = qpd->cwsr_base; > > - memcpy(qpd->cwsr_kaddr, dev->kfd->cwsr_isa, dev->kfd->cwsr_isa_size); > + /* Copy CWSR ISA to buffer using appropriate accessor */ > + iosys_map_memcpy_to(&qpd->cwsr_map, 0, dev->kfd->cwsr_isa, > + dev->kfd->cwsr_isa_size); > > kfd_process_set_trap_debug_flag(&pdd->qpd, > pdd->process->debug_trap_enabled); > > qpd->tma_addr = qpd->tba_addr + KFD_CWSR_TMA_OFFSET; > - pr_debug("set tba :0x%llx, tma:0x%llx, cwsr_kaddr:%p for pqm.\n", > - qpd->tba_addr, qpd->tma_addr, qpd->cwsr_kaddr); > + pr_debug("set tba :0x%llx, tma:0x%llx, cwsr_map:%s at %p for pqm.\n", > + qpd->tba_addr, qpd->tma_addr, > + qpd->cwsr_map.is_iomem ? "iomem" : "system", > + qpd->cwsr_map.is_iomem ? (void *)qpd->cwsr_map.vaddr_iomem : > + qpd->cwsr_map.vaddr); > > return 0; > } > @@ -1536,24 +1563,24 @@ static void > kfd_process_device_destroy_cwsr_dgpu(struct kfd_process_device *pdd) > struct kfd_node *dev = pdd->dev; > struct qcm_process_device *qpd = &pdd->qpd; > > - if (!dev->kfd->cwsr_enabled || !qpd->cwsr_kaddr || !qpd->cwsr_base) > + if (!dev->kfd->cwsr_enabled || iosys_map_is_null(&qpd->cwsr_map) || > !qpd->cwsr_base) > return; > > - kfd_process_free_gpuvm(qpd->cwsr_mem, pdd, &qpd->cwsr_kaddr); > + kfd_process_free_gpuvm_map(qpd->cwsr_mem, pdd, &qpd->cwsr_map); > } > > void kfd_process_set_trap_handler(struct qcm_process_device *qpd, > uint64_t tba_addr, > uint64_t tma_addr) > { > - if (qpd->cwsr_kaddr) { > + if (!iosys_map_is_null(&qpd->cwsr_map)) { > /* KFD trap handler is bound, record as second-level TBA/TMA > * in first-level TMA. First-level trap will jump to second. > */ > - uint64_t *tma = > - (uint64_t *)(qpd->cwsr_kaddr + KFD_CWSR_TMA_OFFSET); > - tma[0] = tba_addr; > - tma[1] = tma_addr; > + iosys_map_wr(&qpd->cwsr_map, KFD_CWSR_TMA_OFFSET, > + uint64_t, tba_addr); > + iosys_map_wr(&qpd->cwsr_map, KFD_CWSR_TMA_OFFSET + > sizeof(uint64_t), > + uint64_t, tma_addr); > } else { > /* No trap handler bound, bind as first-level TBA/TMA. */ > qpd->tba_addr = tba_addr; > @@ -1619,10 +1646,10 @@ bool kfd_process_xnack_mode(struct kfd_process *p, > bool supported) > void kfd_process_set_trap_debug_flag(struct qcm_process_device *qpd, > bool enabled) > { > - if (qpd->cwsr_kaddr) { > - uint64_t *tma = > - (uint64_t *)(qpd->cwsr_kaddr + KFD_CWSR_TMA_OFFSET); > - tma[2] = enabled; > + if (!iosys_map_is_null(&qpd->cwsr_map)) { > + iosys_map_wr(&qpd->cwsr_map, > + KFD_CWSR_TMA_OFFSET + 2 * sizeof(uint64_t), > + uint64_t, enabled); > } > } >
