Re: [PATCH v2 7/8] drm/i915: Create vgpu specific write MMIO to reduce traps

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On 10/22/2014 11:33 PM, Daniel Vetter wrote:
On Wed, Oct 22, 2014 at 08:27:50PM +0800, Yu, Zhang wrote:


On 10/22/2014 12:40 AM, Daniel Vetter wrote:
On Thu, Oct 16, 2014 at 02:24:27PM +0800, Yu Zhang wrote:
In the virtualized environment, forcewake operations are not
necessory for the driver, because mmio accesses will be trapped
and emulated by the host side, and real forcewake operations are
also done in the host. New mmio write handlers are added to directly
call the __raw_i915_write, therefore will reduce many traps and
increase the overall performance for drivers runing in the VM
with Intel GVT-g enhancement.

Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Jike Song <jike.song@xxxxxxxxx>
Signed-off-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
  drivers/gpu/drm/i915/intel_uncore.c | 20 ++++++++++++++++++++
  1 file changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index d5f39f3..ec6d5ce 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -719,6 +719,14 @@ hsw_write##x(struct drm_i915_private *dev_priv, off_t reg, u##x val, bool trace)
  	REG_WRITE_FOOTER; \
  }

+#define __vgpu_write(x) \
+static void \
+vgpu_write##x(struct drm_i915_private *dev_priv, off_t reg, u##x val, bool trace) { \
+	REG_WRITE_HEADER; \
+	__raw_i915_write##x(dev_priv, reg, val); \
+	REG_WRITE_FOOTER; \
+}
+
  static const u32 gen8_shadowed_regs[] = {
  	FORCEWAKE_MT,
  	GEN6_RPNSWREQ,
@@ -813,6 +821,10 @@ __gen4_write(8)
  __gen4_write(16)
  __gen4_write(32)
  __gen4_write(64)
+__vgpu_write(8)
+__vgpu_write(16)
+__vgpu_write(32)
+__vgpu_write(64)

  #undef __chv_write
  #undef __gen8_write
@@ -820,6 +832,7 @@ __gen4_write(64)
  #undef __gen6_write
  #undef __gen5_write
  #undef __gen4_write
+#undef __vgpu_write
  #undef REG_WRITE_FOOTER
  #undef REG_WRITE_HEADER

@@ -950,6 +963,13 @@ void intel_uncore_init(struct drm_device *dev)
  		dev_priv->uncore.funcs.mmio_readq  = gen4_read64;
  		break;
  	}
+
+	if (intel_vgpu_active(dev)) {
+		dev_priv->uncore.funcs.mmio_writeb = vgpu_write8;
+		dev_priv->uncore.funcs.mmio_writew = vgpu_write16;
+		dev_priv->uncore.funcs.mmio_writel = vgpu_write32;
+		dev_priv->uncore.funcs.mmio_writeq = vgpu_write64;

Someone should write a cool macro which uses prepocessor string
concatenation so that we can compress this all to

	ASSIGN_WRITE_MMIO_VFUNCS(vgpu)

Then throw in an ASSIGN_READ_MMIO_VFUNC which looks similarly and this
might actually be pretty. Just an idea for some follow-up cleanup.
-Daniel

Thanks Daniel.
Do you mean something like this:
#define ASSIGN_WRITE_MMIO_VFUNCS(x) \
do {	\
	dev_priv->uncore.funcs.mmio_writeb  = x##_write8;	\
	dev_priv->uncore.funcs.mmio_writew  = x##_write16;	\
	dev_priv->uncore.funcs.mmio_writel  = x##_write32;	\
	dev_priv->uncore.funcs.mmio_writeq  = x##_write64;	\
} while (0)

and then we can use ASSIGN_WRITE_MMIO_VFUNCS(hsw) for hsw and
ASSIGN_WRITE_MMIO_VFUNCS(vgpu) for vgpu, etc?

Yup. Plus the version for assigning READ vfuncs (on many platforms they
don't match up). Probably best if you do this conversion as a prep patch
before the vgt series so that I can merge it right away.
-Daniel
Sure, thanks.
I 'll send this patch later, before our v3 vgpu patch series. :)

Yu

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