Re: [PATCH v2 0/8] Add enlightenments for vGPU

Daniel Vetter
2014-10-21T16:16:25Z

On Fri, Oct 17, 2014 at 01:37:11PM +0800, Yu Zhang wrote:
> Intel GVT-g (previously known as XenGT), is a complete GPU
> virtualization solution with mediated pass-through for 4th
> generation Intel Core processors - Haswell platform. This
> technology presents a virtual full-fledged GPU to each Virtual
> Machine (VM). VMs can directly access performance-critical
> resources, without intervention from the hypervisor in most
> cases, while privileged operations from VMs are trap-and-emulated
> at minimal cost. For detail, please refer to
> https://01.org/xen/blogs/wangbo85/2014/intel-gvt-gxengt-pubic-release
>
> This patch set includes necessary code changes when i915 driver
> runs inside a VM. Though ideally we can run an unmodified i915
> driver in VM, adding such enlightenments can greatly reduce the
> virtualization complexity in orders of magnitude. Code changes
> for the host side, which includes the actual Intel GVT-g
> implementation, were sent out in another patchset.
>
> The primary change introduced here is to implement so-called
> "address space ballooning" technique. XenGT partitions global
> graphics memory among multiple VMs, so each VM can directly
> access a portion of the memory w/o hypervisor's intervention,
> e.g. filling textures and queuing commands. However w/ the
> partitioning an unmodified i915 driver would assume a smaller
> graphics memory starting from address ZERO, so requires XenGT
> core module (vgt) to translate the graphics address between
> 'guest view' and 'host view', for all registers and command
> opcodes which contain a graphics memory address. To reduce the
> complexity, XenGT introduces "address space ballooning", by
> telling the exact partitioning knowledge to each guest i915
> driver, which then reserves and prevents non-allocated portions
> from allocation. Then vgt module only needs to scan and validate
> graphics addresses w/o complexity of translation.
>
> Note: The partitioning of global graphics memory may break some
> applications, with large objects in the aperture, because current
> userspace assumes half of the aperture usable. That would need
> separate fix either in user space (e.g. remove assumption in mesa)
> or in kernel (w/ some faulting mechanism).
>
> The partitioning knowledge is conveyed through a reserved MMIO
> range, called PVINFO, which will be architecturally reserved in
> future hardware generations. Another information carried through
> PVINFO is about the number of fence registers. As a global resource
> XenGT also partitions them among VMs.
>
> Other changes are trivial as optimizations, to either reduce the
> trap overhead or disable power management features which don't
> make sense in a virtualized environment.
>
> Yu Zhang (8):
> drm/i915: Introduce a PV INFO page structure for Intel GVT-g.
> drm/i915: Adds graphic address space ballooning logic
> drm/i915: Partition the fence registers for vgpu in i915 driver
> drm/i915: Disable framebuffer compression for i915 driver in VM
> drm/i915: Add the display switch logic for vgpu in i915 driver
> drm/i915: Disable power management for i915 driver in VM
> drm/i915: Create vgpu specific write MMIO to reduce traps
> drm/i915: Support alias ppgtt in VM if ppgtt is enabled
>
> drivers/gpu/drm/i915/i915_dma.c | 11 +++
> drivers/gpu/drm/i915/i915_drv.h | 12 +++
> drivers/gpu/drm/i915/i915_gem.c | 5 +
> drivers/gpu/drm/i915/i915_gem_gtt.c | 186 +++++++++++++++++++++++++++++++++++-
> drivers/gpu/drm/i915/i915_vgt_if.h | 93 ++++++++++++++++++
> drivers/gpu/drm/i915/intel_pm.c | 8 ++
> drivers/gpu/drm/i915/intel_uncore.c | 22 +++++
> 7 files changed, 334 insertions(+), 3 deletions(-)
> create mode 100644 drivers/gpu/drm/i915/i915_vgt_if.h

I seem to have two v2 versions of this patch series. Anything changed or
why the resend? I didn't see any comment on the older version ...
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch