On 09/19/2014 03:25 PM, Chris Wilson wrote:
Now, given that these are simply trapped memory access, wouldn't it be
simply to have:
struct i915_virtual_gpu {
struct vgt_if *if;
} vgu;
static inline bool intel_vgpu_active(struct drm_i915_private *i915) { return
i915->vgpu.if; }
then you have constructs like
void i915_check_vgpu(struct drm_i915_private *i915)
{
struct vgt_if *if;
if = i915->regs + VGT_PVINFO_PAGE;
if (if->magic != VGT_MAGIC)
return;
if (INTEL_VGT_IF_VERSION !=
INTEL_VGT_IF_VERSION_ENCODE(if->version_major,
if->version_minor))
return;
i915->vgpu.if = if;
}
And later, for example:
if (intel_vgpu_active(dev_priv))
dev_priv->num_fence_regs = dev_priv->vgpu.if->fence_num;
Hi Chris, sorry that I didn't understand you correctly. After discussion
with Yu today, I realized that unfortunately, the vgt_if can't be
dereferenced directly.
There are several reasons:
- dereferencing a MMIO address will be complained by sparse(1)
- for Guest VM, such accesses will be trapped by hypervisor, and
hence emulated correctly; However this doesn't work for Host(e.g.
Domain 0 of Xen, the Linux host KVM resides in). For host, we used
a proactive mechanism to redirect i915 MMIO accesses to vgt,
the GPU device-model, for the sake of central management & sharing
among VMs, including host.
Given that, though technically your code works for Guest, but after the
integration of host support of iGVT, we still need to use I915_READ/I915_WRITE
then. The host patches is soon to posted for your review :)
I should have realized that earlier, sorry!
-Chris
--
Thanks,
Jike
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