[PATCH RFC] drm: add func to better detect wether swiotlb is needed
Koenig, Christian
Christian.Koenig at amd.com
Sat Feb 16 19:00:00 UTC 2019
Am 15.02.19 um 22:29 schrieb Michael D Labriola:
> This commit fixes DRM failures on Xen PV systems that were introduced in
> v4.17 by the following commits:
>
> 82626363 drm: add func to get max iomem address v2
> fd5fd480 drm/amdgpu: only enable swiotlb alloc when need v2
> 1bc3d3cc drm/radeon: only enable swiotlb path when need v2
>
> The introduction of ->need_swiotlb to the ttm_dma_populate() conditionals
> in the radeon and amdgpu device drivers causes Gnome to immediately crash
> on Xen PV systems, returning the user to the login screen. The following
> kernel errors get logged:
>
> [ 28.554259] radeon_dp_aux_transfer_native: 200 callbacks suppressed
> [ 31.219821] radeon 0000:01:00.0: swiotlb buffer is full (sz: 2097152 bytes)
> [ 31.220030] [drm:radeon_gem_object_create [radeon]] *ERROR* Failed to allocate GEM object (16384000, 2, 4096, -14)
> [ 31.226109] radeon 0000:01:00.0: swiotlb buffer is full (sz: 2097152 bytes)
> [ 31.226300] [drm:radeon_gem_object_create [radeon]] *ERROR* Failed to allocate GEM object (16384000, 2, 4096, -14)
> [ 31.300734] gnome-shell[1935]: segfault at 88 ip 00007f39151cd904 sp 00007ffc97611ad8 error 4 in libmutter-cogl.so[7f3915178000+aa000]
> [ 31.300745] Code: 5f c3 0f 1f 40 00 48 8b 47 78 48 8b 40 40 ff e0 66 0f 1f 44 00 00 48 8b 47 78 48 8b 40 48 ff e0 66 0f 1f 44 00 00 48 8b 47 78 <48> 8b 80 88 00 00 00 ff e0 0f 1f 00 48 8b 47 78 48 8b 40 68 ff e0
> [ 38.193302] radeon_dp_aux_transfer_native: 116 callbacks suppressed
> [ 40.009317] radeon 0000:01:00.0: swiotlb buffer is full (sz: 2097152 bytes)
> [ 40.009488] [drm:radeon_gem_object_create [radeon]] *ERROR* Failed to allocate GEM object (16384000, 2, 4096, -14)
> [ 40.015114] radeon 0000:01:00.0: swiotlb buffer is full (sz: 2097152 bytes)
> [ 40.015297] [drm:radeon_gem_object_create [radeon]] *ERROR* Failed to allocate GEM object (16384000, 2, 4096, -14)
> [ 40.028302] gnome-shell[2431]: segfault at 2dadf40 ip 0000000002dadf40 sp 00007ffcd24ea5f8 error 15
> [ 40.028306] Code: 20 6e 31 00 00 00 00 00 00 00 00 37 e3 3d 2d 7f 00 00 80 f4 e6 3d 2d 7f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <00> 00 00 00 00 00 00 00 c1 00 00 00 00 00 00 00 80 e1 d2 03 00 00
>
> This commit renames drm_get_max_iomem() to drm_need_swiotlb(), adds a
> xen_pv_domain() check to it, and moves the bit shifting comparison that
> always follows its usage into the function (simplifying the drm driver
> code).
You signed of by line is missing. Apart from that it looks like a good
fix to me.
But the question is why does Xen needs dma_alloc_coherent() ?
Using dma_alloc_coherent() is really just a fallback path and we need to
disable a bunch of userspace features when going down that route.
Regards,
Christian.
> ---
> drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c | 2 +-
> drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c | 2 +-
> drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c | 2 +-
> drivers/gpu/drm/drm_memory.c | 19 ++++++++++++++++---
> drivers/gpu/drm/radeon/radeon_device.c | 2 +-
> include/drm/drm_cache.h | 2 +-
> 6 files changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> index 910c4ce..6bc0266 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> @@ -1029,7 +1029,7 @@ static int gmc_v7_0_sw_init(void *handle)
> pci_set_consistent_dma_mask(adev->pdev, DMA_BIT_MASK(32));
> pr_warn("amdgpu: No coherent DMA available\n");
> }
> - adev->need_swiotlb = drm_get_max_iomem() > ((u64)1 << dma_bits);
> + adev->need_swiotlb = drm_need_swiotlb(dma_bits);
>
> r = gmc_v7_0_init_microcode(adev);
> if (r) {
> diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
> index 747c068..8638adf 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
> @@ -1155,7 +1155,7 @@ static int gmc_v8_0_sw_init(void *handle)
> pci_set_consistent_dma_mask(adev->pdev, DMA_BIT_MASK(32));
> pr_warn("amdgpu: No coherent DMA available\n");
> }
> - adev->need_swiotlb = drm_get_max_iomem() > ((u64)1 << dma_bits);
> + adev->need_swiotlb = drm_need_swiotlb(dma_bits);
>
> r = gmc_v8_0_init_microcode(adev);
> if (r) {
> diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
> index f35d7a5..4f67093 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
> @@ -989,7 +989,7 @@ static int gmc_v9_0_sw_init(void *handle)
> pci_set_consistent_dma_mask(adev->pdev, DMA_BIT_MASK(32));
> printk(KERN_WARNING "amdgpu: No coherent DMA available.\n");
> }
> - adev->need_swiotlb = drm_get_max_iomem() > ((u64)1 << dma_bits);
> + adev->need_swiotlb = drm_need_swiotlb(dma_bits);
>
> if (adev->asic_type == CHIP_VEGA20) {
> r = gfxhub_v1_1_get_xgmi_info(adev);
> diff --git a/drivers/gpu/drm/drm_memory.c b/drivers/gpu/drm/drm_memory.c
> index d69e4fc..6af59a6 100644
> --- a/drivers/gpu/drm/drm_memory.c
> +++ b/drivers/gpu/drm/drm_memory.c
> @@ -35,6 +35,7 @@
>
> #include <linux/highmem.h>
> #include <linux/export.h>
> +#include <xen/xen.h>
> #include <drm/drmP.h>
> #include "drm_legacy.h"
>
> @@ -150,15 +151,27 @@ void drm_legacy_ioremapfree(struct drm_local_map *map, struct drm_device *dev)
> }
> EXPORT_SYMBOL(drm_legacy_ioremapfree);
>
> -u64 drm_get_max_iomem(void)
> +bool drm_need_swiotlb(int dma_bits)
> {
> struct resource *tmp;
> resource_size_t max_iomem = 0;
>
> + /*
> + * Xen paravirtual hosts require swiotlb regardless of requested dma
> + * transfer size.
> + *
> + * NOTE: Really, what it requires is use of the dma_alloc_coherent
> + * allocator used in ttm_dma_populate() instead of
> + * ttm_populate_and_map_pages(), which bounce buffers so much in
> + * Xen it leads to swiotlb buffer exhaustion.
> + */
> + if (xen_pv_domain())
> + return true;
> +
> for (tmp = iomem_resource.child; tmp; tmp = tmp->sibling) {
> max_iomem = max(max_iomem, tmp->end);
> }
>
> - return max_iomem;
> + return max_iomem > ((u64)1 << dma_bits);
> }
> -EXPORT_SYMBOL(drm_get_max_iomem);
> +EXPORT_SYMBOL(drm_need_swiotlb);
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
> index 59c8a66..a1d3c62 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1387,7 +1387,7 @@ int radeon_device_init(struct radeon_device *rdev,
> pci_set_consistent_dma_mask(rdev->pdev, DMA_BIT_MASK(32));
> pr_warn("radeon: No coherent DMA available\n");
> }
> - rdev->need_swiotlb = drm_get_max_iomem() > ((u64)1 << dma_bits);
> + rdev->need_swiotlb = drm_need_swiotlb(dma_bits);
>
> /* Registers mapping */
> /* TODO: block userspace mapping of io register */
> diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h
> index bfe1639..633eaaf 100644
> --- a/include/drm/drm_cache.h
> +++ b/include/drm/drm_cache.h
> @@ -38,7 +38,7 @@
> void drm_clflush_pages(struct page *pages[], unsigned long num_pages);
> void drm_clflush_sg(struct sg_table *st);
> void drm_clflush_virt_range(void *addr, unsigned long length);
> -u64 drm_get_max_iomem(void);
> +bool drm_need_swiotlb(int dma_bits);
>
>
> static inline bool drm_arch_can_wc_memory(void)
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