| Message ID | 20210601074654.3103-8-thomas.hellstrom@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Move LMEM (VRAM) management over to TTM | expand |
On Tue, 01 Jun 2021, Thomas Hellström <thomas.hellstrom@linux.intel.com> wrote: > Reading out of write-combining mapped memory is typically very slow > since the CPU doesn't prefetch. However some archs have special > instructions to do this. > > So add a best-effort memcpy_from_wc taking dma-buf-map pointer > arguments that attempts to use a fast prefetching memcpy and > otherwise falls back to ordinary memcopies, taking the iomem tagging > into account. > > The code is largely copied from i915_memcpy_from_wc. > > Cc: Daniel Vetter <daniel@ffwll.ch> > Cc: Christian König <christian.koenig@amd.com> > Suggested-by: Daniel Vetter <daniel@ffwll.ch> > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> > Acked-by: Christian König <christian.koenig@amd.com> > Acked-by: Daniel Vetter <daniel@ffwll.ch> > --- > v7: > - Perform a memcpy even if warning with in_interrupt(). Suggested by > Christian König. > - Fix compilation failure on !X86 (Reported by kernel test robot > lkp@intel.com) > v8: > - Skip kerneldoc for drm_memcpy_init_early() > - Export drm_memcpy_from_wc() also for non-x86. > --- > Documentation/gpu/drm-mm.rst | 2 +- > drivers/gpu/drm/drm_cache.c | 148 +++++++++++++++++++++++++++++++++++ > drivers/gpu/drm/drm_drv.c | 2 + > include/drm/drm_cache.h | 7 ++ > 4 files changed, 158 insertions(+), 1 deletion(-) > > diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst > index 21be6deadc12..c66058c5bce7 100644 > --- a/Documentation/gpu/drm-mm.rst > +++ b/Documentation/gpu/drm-mm.rst > @@ -469,7 +469,7 @@ DRM MM Range Allocator Function References > .. kernel-doc:: drivers/gpu/drm/drm_mm.c > :export: > > -DRM Cache Handling > +DRM Cache Handling and Fast WC memcpy() > ================== The title underline needs to be as long as the title. BR, Jani. > > .. kernel-doc:: drivers/gpu/drm/drm_cache.c > diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c > index 79a50ef1250f..546599f19a93 100644 > --- a/drivers/gpu/drm/drm_cache.c > +++ b/drivers/gpu/drm/drm_cache.c > @@ -28,6 +28,7 @@ > * Authors: Thomas Hellström <thomas-at-tungstengraphics-dot-com> > */ > > +#include <linux/dma-buf-map.h> > #include <linux/export.h> > #include <linux/highmem.h> > #include <linux/mem_encrypt.h> > @@ -35,6 +36,9 @@ > > #include <drm/drm_cache.h> > > +/* A small bounce buffer that fits on the stack. */ > +#define MEMCPY_BOUNCE_SIZE 128 > + > #if defined(CONFIG_X86) > #include <asm/smp.h> > > @@ -209,3 +213,147 @@ bool drm_need_swiotlb(int dma_bits) > return max_iomem > ((u64)1 << dma_bits); > } > EXPORT_SYMBOL(drm_need_swiotlb); > + > +static void memcpy_fallback(struct dma_buf_map *dst, > + const struct dma_buf_map *src, > + unsigned long len) > +{ > + if (!dst->is_iomem && !src->is_iomem) { > + memcpy(dst->vaddr, src->vaddr, len); > + } else if (!src->is_iomem) { > + dma_buf_map_memcpy_to(dst, src->vaddr, len); > + } else if (!dst->is_iomem) { > + memcpy_fromio(dst->vaddr, src->vaddr_iomem, len); > + } else { > + /* > + * Bounce size is not performance tuned, but using a > + * bounce buffer like this is significantly faster than > + * resorting to ioreadxx() + iowritexx(). > + */ > + char bounce[MEMCPY_BOUNCE_SIZE]; > + void __iomem *_src = src->vaddr_iomem; > + void __iomem *_dst = dst->vaddr_iomem; > + > + while (len >= MEMCPY_BOUNCE_SIZE) { > + memcpy_fromio(bounce, _src, MEMCPY_BOUNCE_SIZE); > + memcpy_toio(_dst, bounce, MEMCPY_BOUNCE_SIZE); > + _src += MEMCPY_BOUNCE_SIZE; > + _dst += MEMCPY_BOUNCE_SIZE; > + len -= MEMCPY_BOUNCE_SIZE; > + } > + if (len) { > + memcpy_fromio(bounce, _src, MEMCPY_BOUNCE_SIZE); > + memcpy_toio(_dst, bounce, MEMCPY_BOUNCE_SIZE); > + } > + } > +} > + > +#ifdef CONFIG_X86 > + > +static DEFINE_STATIC_KEY_FALSE(has_movntdqa); > + > +static void __memcpy_ntdqa(void *dst, const void *src, unsigned long len) > +{ > + kernel_fpu_begin(); > + > + while (len >= 4) { > + asm("movntdqa (%0), %%xmm0\n" > + "movntdqa 16(%0), %%xmm1\n" > + "movntdqa 32(%0), %%xmm2\n" > + "movntdqa 48(%0), %%xmm3\n" > + "movaps %%xmm0, (%1)\n" > + "movaps %%xmm1, 16(%1)\n" > + "movaps %%xmm2, 32(%1)\n" > + "movaps %%xmm3, 48(%1)\n" > + :: "r" (src), "r" (dst) : "memory"); > + src += 64; > + dst += 64; > + len -= 4; > + } > + while (len--) { > + asm("movntdqa (%0), %%xmm0\n" > + "movaps %%xmm0, (%1)\n" > + :: "r" (src), "r" (dst) : "memory"); > + src += 16; > + dst += 16; > + } > + > + kernel_fpu_end(); > +} > + > +/* > + * __drm_memcpy_from_wc copies @len bytes from @src to @dst using > + * non-temporal instructions where available. Note that all arguments > + * (@src, @dst) must be aligned to 16 bytes and @len must be a multiple > + * of 16. > + */ > +static void __drm_memcpy_from_wc(void *dst, const void *src, unsigned long len) > +{ > + if (unlikely(((unsigned long)dst | (unsigned long)src | len) & 15)) > + memcpy(dst, src, len); > + else if (likely(len)) > + __memcpy_ntdqa(dst, src, len >> 4); > +} > + > +/** > + * drm_memcpy_from_wc - Perform the fastest available memcpy from a source > + * that may be WC. > + * @dst: The destination pointer > + * @src: The source pointer > + * @len: The size of the area o transfer in bytes > + * > + * Tries an arch optimized memcpy for prefetching reading out of a WC region, > + * and if no such beast is available, falls back to a normal memcpy. > + */ > +void drm_memcpy_from_wc(struct dma_buf_map *dst, > + const struct dma_buf_map *src, > + unsigned long len) > +{ > + if (WARN_ON(in_interrupt())) { > + memcpy_fallback(dst, src, len); > + return; > + } > + > + if (static_branch_likely(&has_movntdqa)) { > + __drm_memcpy_from_wc(dst->is_iomem ? > + (void __force *)dst->vaddr_iomem : > + dst->vaddr, > + src->is_iomem ? > + (void const __force *)src->vaddr_iomem : > + src->vaddr, > + len); > + return; > + } > + > + memcpy_fallback(dst, src, len); > +} > +EXPORT_SYMBOL(drm_memcpy_from_wc); > + > +/* > + * drm_memcpy_init_early - One time initialization of the WC memcpy code > + */ > +void drm_memcpy_init_early(void) > +{ > + /* > + * Some hypervisors (e.g. KVM) don't support VEX-prefix instructions > + * emulation. So don't enable movntdqa in hypervisor guest. > + */ > + if (static_cpu_has(X86_FEATURE_XMM4_1) && > + !boot_cpu_has(X86_FEATURE_HYPERVISOR)) > + static_branch_enable(&has_movntdqa); > +} > +#else > +void drm_memcpy_from_wc(struct dma_buf_map *dst, > + const struct dma_buf_map *src, > + unsigned long len) > +{ > + WARN_ON(in_interrupt()); > + > + memcpy_fallback(dst, src, len); > +} > +EXPORT_SYMBOL(drm_memcpy_from_wc); > + > +void drm_memcpy_init_early(void) > +{ > +} > +#endif /* CONFIG_X86 */ > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c > index 3d8d68a98b95..8804ec7d3215 100644 > --- a/drivers/gpu/drm/drm_drv.c > +++ b/drivers/gpu/drm/drm_drv.c > @@ -35,6 +35,7 @@ > #include <linux/slab.h> > #include <linux/srcu.h> > > +#include <drm/drm_cache.h> > #include <drm/drm_client.h> > #include <drm/drm_color_mgmt.h> > #include <drm/drm_drv.h> > @@ -1041,6 +1042,7 @@ static int __init drm_core_init(void) > > drm_connector_ida_init(); > idr_init(&drm_minors_idr); > + drm_memcpy_init_early(); > > ret = drm_sysfs_init(); > if (ret < 0) { > diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h > index e9ad4863d915..cc9de1632dd3 100644 > --- a/include/drm/drm_cache.h > +++ b/include/drm/drm_cache.h > @@ -35,6 +35,8 @@ > > #include <linux/scatterlist.h> > > +struct dma_buf_map; > + > 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); > @@ -70,4 +72,9 @@ static inline bool drm_arch_can_wc_memory(void) > #endif > } > > +void drm_memcpy_init_early(void); > + > +void drm_memcpy_from_wc(struct dma_buf_map *dst, > + const struct dma_buf_map *src, > + unsigned long len); > #endif
On 6/1/21 2:27 PM, Jani Nikula wrote: > On Tue, 01 Jun 2021, Thomas Hellström <thomas.hellstrom@linux.intel.com> wrote: >> Reading out of write-combining mapped memory is typically very slow >> since the CPU doesn't prefetch. However some archs have special >> instructions to do this. >> >> So add a best-effort memcpy_from_wc taking dma-buf-map pointer >> arguments that attempts to use a fast prefetching memcpy and >> otherwise falls back to ordinary memcopies, taking the iomem tagging >> into account. >> >> The code is largely copied from i915_memcpy_from_wc. >> >> Cc: Daniel Vetter <daniel@ffwll.ch> >> Cc: Christian König <christian.koenig@amd.com> >> Suggested-by: Daniel Vetter <daniel@ffwll.ch> >> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> >> Acked-by: Christian König <christian.koenig@amd.com> >> Acked-by: Daniel Vetter <daniel@ffwll.ch> >> --- >> v7: >> - Perform a memcpy even if warning with in_interrupt(). Suggested by >> Christian König. >> - Fix compilation failure on !X86 (Reported by kernel test robot >> lkp@intel.com) >> v8: >> - Skip kerneldoc for drm_memcpy_init_early() >> - Export drm_memcpy_from_wc() also for non-x86. >> --- >> Documentation/gpu/drm-mm.rst | 2 +- >> drivers/gpu/drm/drm_cache.c | 148 +++++++++++++++++++++++++++++++++++ >> drivers/gpu/drm/drm_drv.c | 2 + >> include/drm/drm_cache.h | 7 ++ >> 4 files changed, 158 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst >> index 21be6deadc12..c66058c5bce7 100644 >> --- a/Documentation/gpu/drm-mm.rst >> +++ b/Documentation/gpu/drm-mm.rst >> @@ -469,7 +469,7 @@ DRM MM Range Allocator Function References >> .. kernel-doc:: drivers/gpu/drm/drm_mm.c >> :export: >> >> -DRM Cache Handling >> +DRM Cache Handling and Fast WC memcpy() >> ================== > The title underline needs to be as long as the title. > > BR, > Jani. Thanks, Jani. I think Daniel was trying to point this out to me as well with limited success. It's fixed now. /Thomas
diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst index 21be6deadc12..c66058c5bce7 100644 --- a/Documentation/gpu/drm-mm.rst +++ b/Documentation/gpu/drm-mm.rst @@ -469,7 +469,7 @@ DRM MM Range Allocator Function References .. kernel-doc:: drivers/gpu/drm/drm_mm.c :export: -DRM Cache Handling +DRM Cache Handling and Fast WC memcpy() ================== .. kernel-doc:: drivers/gpu/drm/drm_cache.c diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c index 79a50ef1250f..546599f19a93 100644 --- a/drivers/gpu/drm/drm_cache.c +++ b/drivers/gpu/drm/drm_cache.c @@ -28,6 +28,7 @@ * Authors: Thomas Hellström <thomas-at-tungstengraphics-dot-com> */ +#include <linux/dma-buf-map.h> #include <linux/export.h> #include <linux/highmem.h> #include <linux/mem_encrypt.h> @@ -35,6 +36,9 @@ #include <drm/drm_cache.h> +/* A small bounce buffer that fits on the stack. */ +#define MEMCPY_BOUNCE_SIZE 128 + #if defined(CONFIG_X86) #include <asm/smp.h> @@ -209,3 +213,147 @@ bool drm_need_swiotlb(int dma_bits) return max_iomem > ((u64)1 << dma_bits); } EXPORT_SYMBOL(drm_need_swiotlb); + +static void memcpy_fallback(struct dma_buf_map *dst, + const struct dma_buf_map *src, + unsigned long len) +{ + if (!dst->is_iomem && !src->is_iomem) { + memcpy(dst->vaddr, src->vaddr, len); + } else if (!src->is_iomem) { + dma_buf_map_memcpy_to(dst, src->vaddr, len); + } else if (!dst->is_iomem) { + memcpy_fromio(dst->vaddr, src->vaddr_iomem, len); + } else { + /* + * Bounce size is not performance tuned, but using a + * bounce buffer like this is significantly faster than + * resorting to ioreadxx() + iowritexx(). + */ + char bounce[MEMCPY_BOUNCE_SIZE]; + void __iomem *_src = src->vaddr_iomem; + void __iomem *_dst = dst->vaddr_iomem; + + while (len >= MEMCPY_BOUNCE_SIZE) { + memcpy_fromio(bounce, _src, MEMCPY_BOUNCE_SIZE); + memcpy_toio(_dst, bounce, MEMCPY_BOUNCE_SIZE); + _src += MEMCPY_BOUNCE_SIZE; + _dst += MEMCPY_BOUNCE_SIZE; + len -= MEMCPY_BOUNCE_SIZE; + } + if (len) { + memcpy_fromio(bounce, _src, MEMCPY_BOUNCE_SIZE); + memcpy_toio(_dst, bounce, MEMCPY_BOUNCE_SIZE); + } + } +} + +#ifdef CONFIG_X86 + +static DEFINE_STATIC_KEY_FALSE(has_movntdqa); + +static void __memcpy_ntdqa(void *dst, const void *src, unsigned long len) +{ + kernel_fpu_begin(); + + while (len >= 4) { + asm("movntdqa (%0), %%xmm0\n" + "movntdqa 16(%0), %%xmm1\n" + "movntdqa 32(%0), %%xmm2\n" + "movntdqa 48(%0), %%xmm3\n" + "movaps %%xmm0, (%1)\n" + "movaps %%xmm1, 16(%1)\n" + "movaps %%xmm2, 32(%1)\n" + "movaps %%xmm3, 48(%1)\n" + :: "r" (src), "r" (dst) : "memory"); + src += 64; + dst += 64; + len -= 4; + } + while (len--) { + asm("movntdqa (%0), %%xmm0\n" + "movaps %%xmm0, (%1)\n" + :: "r" (src), "r" (dst) : "memory"); + src += 16; + dst += 16; + } + + kernel_fpu_end(); +} + +/* + * __drm_memcpy_from_wc copies @len bytes from @src to @dst using + * non-temporal instructions where available. Note that all arguments + * (@src, @dst) must be aligned to 16 bytes and @len must be a multiple + * of 16. + */ +static void __drm_memcpy_from_wc(void *dst, const void *src, unsigned long len) +{ + if (unlikely(((unsigned long)dst | (unsigned long)src | len) & 15)) + memcpy(dst, src, len); + else if (likely(len)) + __memcpy_ntdqa(dst, src, len >> 4); +} + +/** + * drm_memcpy_from_wc - Perform the fastest available memcpy from a source + * that may be WC. + * @dst: The destination pointer + * @src: The source pointer + * @len: The size of the area o transfer in bytes + * + * Tries an arch optimized memcpy for prefetching reading out of a WC region, + * and if no such beast is available, falls back to a normal memcpy. + */ +void drm_memcpy_from_wc(struct dma_buf_map *dst, + const struct dma_buf_map *src, + unsigned long len) +{ + if (WARN_ON(in_interrupt())) { + memcpy_fallback(dst, src, len); + return; + } + + if (static_branch_likely(&has_movntdqa)) { + __drm_memcpy_from_wc(dst->is_iomem ? + (void __force *)dst->vaddr_iomem : + dst->vaddr, + src->is_iomem ? + (void const __force *)src->vaddr_iomem : + src->vaddr, + len); + return; + } + + memcpy_fallback(dst, src, len); +} +EXPORT_SYMBOL(drm_memcpy_from_wc); + +/* + * drm_memcpy_init_early - One time initialization of the WC memcpy code + */ +void drm_memcpy_init_early(void) +{ + /* + * Some hypervisors (e.g. KVM) don't support VEX-prefix instructions + * emulation. So don't enable movntdqa in hypervisor guest. + */ + if (static_cpu_has(X86_FEATURE_XMM4_1) && + !boot_cpu_has(X86_FEATURE_HYPERVISOR)) + static_branch_enable(&has_movntdqa); +} +#else +void drm_memcpy_from_wc(struct dma_buf_map *dst, + const struct dma_buf_map *src, + unsigned long len) +{ + WARN_ON(in_interrupt()); + + memcpy_fallback(dst, src, len); +} +EXPORT_SYMBOL(drm_memcpy_from_wc); + +void drm_memcpy_init_early(void) +{ +} +#endif /* CONFIG_X86 */ diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 3d8d68a98b95..8804ec7d3215 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -35,6 +35,7 @@ #include <linux/slab.h> #include <linux/srcu.h> +#include <drm/drm_cache.h> #include <drm/drm_client.h> #include <drm/drm_color_mgmt.h> #include <drm/drm_drv.h> @@ -1041,6 +1042,7 @@ static int __init drm_core_init(void) drm_connector_ida_init(); idr_init(&drm_minors_idr); + drm_memcpy_init_early(); ret = drm_sysfs_init(); if (ret < 0) { diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h index e9ad4863d915..cc9de1632dd3 100644 --- a/include/drm/drm_cache.h +++ b/include/drm/drm_cache.h @@ -35,6 +35,8 @@ #include <linux/scatterlist.h> +struct dma_buf_map; + 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); @@ -70,4 +72,9 @@ static inline bool drm_arch_can_wc_memory(void) #endif } +void drm_memcpy_init_early(void); + +void drm_memcpy_from_wc(struct dma_buf_map *dst, + const struct dma_buf_map *src, + unsigned long len); #endif