[PATCH] drm/amdkfd: Relocate TBA/TMA to opposite side of VM hole (v2)
Arunpravin Paneer Selvam
arunpravin.paneerselvam at amd.com
Mon Jan 29 16:50:09 UTC 2024
Hi Felix,
On 1/29/2024 8:24 PM, Felix Kuehling wrote:
> On 2024-01-29 3:45, Yu, Lang wrote:
>> [AMD Official Use Only - General]
>>
>>> -----Original Message-----
>>> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
>>> Felix
>>> Kuehling
>>> Sent: Friday, January 26, 2024 6:28 AM
>>> To: amd-gfx at lists.freedesktop.org
>>> Cc: Cornwall, Jay <Jay.Cornwall at amd.com>; Koenig, Christian
>>> <Christian.Koenig at amd.com>; Paneer Selvam, Arunpravin
>>> <Arunpravin.PaneerSelvam at amd.com>
>>> Subject: [PATCH] drm/amdkfd: Relocate TBA/TMA to opposite side of VM
>>> hole (v2)
>>>
>>> The TBA and TMA, along with an unused IB allocation, reside at low
>>> addresses in
>>> the VM address space. A stray VM fault which hits these pages must
>>> be serviced
>>> by making their page table entries invalid.
>>> The scheduler depends upon these pages being resident and fails,
>>> preventing a
>>> debugger from inspecting the failure state.
>>>
>>> By relocating these pages above 47 bits in the VM address space they
>>> can only be
>>> reached when bits [63:48] are set to 1. This makes it much less
>>> likely for a
>>> misbehaving program to generate accesses to them.
>>> The current placement at VA (PAGE_SIZE*2) is readily hit by a NULL
>>> access with a
>>> small offset.
>>>
>>> v2:
>>> - Move it to the reserved space to avoid concflicts with Mesa
>>> - Add macros to make reserved space management easier
>>>
>>> Cc: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam at amd.com>
>>> Cc: Christian Koenig <christian.koenig at amd.com>
>>> Signed-off-by: Jay Cornwall <jay.cornwall at amd.com>
>>> Signed-off-by: Felix Kuehling <felix.kuehling at amd.com>
>>> ---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c | 4 +--
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_seq64.c | 7 ++---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 12 ++++++--
>>> drivers/gpu/drm/amd/amdkfd/kfd_flat_memory.c | 30 +++++++++++---------
>>> 4 files changed, 30 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
>>> index 823d31f4a2a3..53d0a458d78e 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
>>> @@ -28,9 +28,9 @@
>>>
>>> uint64_t amdgpu_csa_vaddr(struct amdgpu_device *adev) {
>>> - uint64_t addr = adev->vm_manager.max_pfn <<
>>> AMDGPU_GPU_PAGE_SHIFT;
>>> + uint64_t addr = AMDGPU_VA_RESERVED_CSA_START(
>>> + adev->vm_manager.max_pfn << AMDGPU_GPU_PAGE_SHIFT);
>>>
>>> - addr -= AMDGPU_VA_RESERVED_CSA_SIZE;
>>> addr = amdgpu_gmc_sign_extend(addr);
>>>
>>> return addr;
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_seq64.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_seq64.c
>>> index 3d0d56087d41..9e769ef50f2e 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_seq64.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_seq64.c
>>> @@ -45,11 +45,8 @@
>>> */
>>> static inline u64 amdgpu_seq64_get_va_base(struct amdgpu_device
>>> *adev) {
>>> - u64 addr = adev->vm_manager.max_pfn << AMDGPU_GPU_PAGE_SHIFT;
>>> -
>>> - addr -= AMDGPU_VA_RESERVED_TOP;
>>> -
>>> - return addr;
>>> + return AMDGPU_VA_RESERVED_SEQ64_START(
>>> + adev->vm_manager.max_pfn << AMDGPU_GPU_PAGE_SHIFT);
>>> }
>>>
>>> /**
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
>>> index 666698a57192..f23b6153d310 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
>>> @@ -135,11 +135,19 @@ struct amdgpu_mem_stats; #define
>>> AMDGPU_IS_MMHUB0(x) ((x) >= AMDGPU_MMHUB0_START && (x) <
>>> AMDGPU_MMHUB1_START) #define AMDGPU_IS_MMHUB1(x) ((x) >=
>>> AMDGPU_MMHUB1_START && (x) < AMDGPU_MAX_VMHUBS)
>>>
>>> -/* Reserve 2MB at top/bottom of address space for kernel use */
>>> +/* Reserve space at top/bottom of address space for kernel use */
>>> #define AMDGPU_VA_RESERVED_CSA_SIZE (2ULL << 20)
>>> +#define AMDGPU_VA_RESERVED_CSA_START(top) ((top) \
>>> + -
>>> AMDGPU_VA_RESERVED_CSA_SIZE)
>>> #define AMDGPU_VA_RESERVED_SEQ64_SIZE (2ULL << 20)
>>> +#define AMDGPU_VA_RESERVED_SEQ64_START(top)
>>> (AMDGPU_VA_RESERVED_CSA_START(top) \
>>> + -
>>> AMDGPU_VA_RESERVED_SEQ64_SIZE)
>>> +#define AMDGPU_VA_RESERVED_TRAP_SIZE (2ULL << 12)
>>> +#define AMDGPU_VA_RESERVED_TRAP_START(top)
>>> (AMDGPU_VA_RESERVED_SEQ64_START(top) \
>>> + -
>>> AMDGPU_VA_RESERVED_TRAP_SIZE)
>>> #define AMDGPU_VA_RESERVED_BOTTOM (2ULL << 20)
>>> -#define AMDGPU_VA_RESERVED_TOP
>>> (AMDGPU_VA_RESERVED_SEQ64_SIZE + \
>>> +#define AMDGPU_VA_RESERVED_TOP
>>> (AMDGPU_VA_RESERVED_TRAP_SIZE + \
>>> +
>>> AMDGPU_VA_RESERVED_SEQ64_SIZE + \
>>>
>>> AMDGPU_VA_RESERVED_CSA_SIZE)
>>>
>>> /* See vm_update_mode */
>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_flat_memory.c
>>> b/drivers/gpu/drm/amd/amdkfd/kfd_flat_memory.c
>>> index 6604a3f99c5e..f899cce25b2a 100644
>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_flat_memory.c
>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_flat_memory.c
>>> @@ -36,6 +36,7 @@
>>> #include <linux/mm.h>
>>> #include <linux/mman.h>
>>> #include <linux/processor.h>
>>> +#include "amdgpu_vm.h"
>>>
>>> /*
>>> * The primary memory I/O features being added for revisions of
>>> gfxip @@ -
>>> 326,10 +327,16 @@ static void kfd_init_apertures_vi(struct
>>> kfd_process_device
>>> *pdd, uint8_t id)
>>> * with small reserved space for kernel.
>>> * Set them to CANONICAL addresses.
>>> */
>>> - pdd->gpuvm_base = SVM_USER_BASE;
>>> + pdd->gpuvm_base = max(SVM_USER_BASE,
>>> AMDGPU_VA_RESERVED_BOTTOM);
>>> pdd->gpuvm_limit =
>>> pdd->dev->kfd->shared_resources.gpuvm_size - 1;
>>>
>>> + /* dGPUs: the reserved space for kernel
>>> + * before SVM
>>> + */
>>> + pdd->qpd.cwsr_base = SVM_CWSR_BASE;
>>> + pdd->qpd.ib_base = SVM_IB_BASE;
>>> +
>>> pdd->scratch_base = MAKE_SCRATCH_APP_BASE_VI();
>>> pdd->scratch_limit = MAKE_SCRATCH_APP_LIMIT(pdd->scratch_base);
>>> }
>>> @@ -339,18 +346,19 @@ static void kfd_init_apertures_v9(struct
>>> kfd_process_device *pdd, uint8_t id)
>>> pdd->lds_base = MAKE_LDS_APP_BASE_V9();
>>> pdd->lds_limit = MAKE_LDS_APP_LIMIT(pdd->lds_base);
>>>
>>> - /* Raven needs SVM to support graphic handle, etc. Leave
>>> the small
>>> - * reserved space before SVM on Raven as well, even though
>>> we don't
>>> - * have to.
>>> - * Set gpuvm_base and gpuvm_limit to CANONICAL addresses so
>>> that they
>>> - * are used in Thunk to reserve SVM.
>>> - */
>>> - pdd->gpuvm_base = SVM_USER_BASE;
>>> + pdd->gpuvm_base = AMDGPU_VA_RESERVED_BOTTOM;
>> Hi Felix,
>>
>> pdd->gpuvm_base changes from 16KB to 2MB after this patch.
>>
>> The default mmap_min_addr(/proc/sys/vm/mmap_min_addr) is 64KB.
>>
>> That means user could get a CPU VA < 2MB while the corresponding GPU
>> VA has been reserved. Will this break SVM?
>
> It could break SVM if a process tries to map or access something below
> 2MB. I'm not sure what AMDGPU_VA_RESERVED_BOTTOM is used for in the
> GPU page tables. But if it's causing problems for real applications
> with SVM, we should look into lowering that reservation.
>
We have decided to keep AMDGPU_VA_RESERVED_BOTTOM free for catching NULL
pointer dereferences.
Regards,
Arun.
> Regards,
> Felix
>
>
>>
>> Regards,
>> Lang
>>
>>> pdd->gpuvm_limit =
>>> pdd->dev->kfd->shared_resources.gpuvm_size - 1;
>>>
>>> pdd->scratch_base = MAKE_SCRATCH_APP_BASE_V9();
>>> pdd->scratch_limit = MAKE_SCRATCH_APP_LIMIT(pdd->scratch_base);
>>> +
>>> + /*
>>> + * Place TBA/TMA on opposite side of VM hole to prevent
>>> + * stray faults from triggering SVM on these pages.
>>> + */
>>> + pdd->qpd.cwsr_base = AMDGPU_VA_RESERVED_TRAP_START(
>>> + pdd->dev->adev->vm_manager.max_pfn <<
>>> AMDGPU_GPU_PAGE_SHIFT);
>>> }
>>>
>>> int kfd_init_apertures(struct kfd_process *process) @@ -407,12
>>> +415,6 @@ int
>>> kfd_init_apertures(struct kfd_process *process)
>>> return -EINVAL;
>>> }
>>> }
>>> -
>>> - /* dGPUs: the reserved space for kernel
>>> - * before SVM
>>> - */
>>> - pdd->qpd.cwsr_base = SVM_CWSR_BASE;
>>> - pdd->qpd.ib_base = SVM_IB_BASE;
>>> }
>>>
>>> dev_dbg(kfd_device, "node id %u\n", id);
>>> --
>>> 2.34.1
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