gvt: refine function emulate_mmio_read/write
Zhang, Pei
pei.zhang at intel.com
Fri Dec 8 03:06:25 UTC 2017
> -----Original Message-----
> From: Zhenyu Wang [mailto:zhenyuw at linux.intel.com]
> Sent: Friday, December 8, 2017 10:52 AM
> To: Zhang, Pei <pei.zhang at intel.com>
> Cc: intel-gvt-dev at lists.freedesktop.org
> Subject: Re: gvt: refine function emulate_mmio_read/write
>
> On 2017.12.06 15:50:34 +0800, Pei Zhang wrote:
> > These 2 functions are coded by multiple person in multiple patches.
> > The 'return' and 'goto err' are mix-used in same place, which cause
> > the function looks disorder. Unify to use only 'goto' so that the gvt
> > lock is acquired in one place and released in one place.
> >
> > Signed-off-by: Pei Zhang <pei.zhang at intel.com>
> > ---
> > drivers/gpu/drm/i915/gvt/mmio.c | 32 ++++++++++++++------------------
> > 1 file changed, 14 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gvt/mmio.c
> > b/drivers/gpu/drm/i915/gvt/mmio.c index 980ec89..24f9c2f 100644
> > --- a/drivers/gpu/drm/i915/gvt/mmio.c
> > +++ b/drivers/gpu/drm/i915/gvt/mmio.c
> > @@ -126,13 +126,12 @@ int intel_vgpu_emulate_mmio_read(struct
> intel_vgpu *vgpu, uint64_t pa,
> > unsigned int offset = 0;
> > int ret = -EINVAL;
> >
> > -
> > if (vgpu->failsafe) {
> > failsafe_emulate_mmio_rw(vgpu, pa, p_data, bytes, true);
> > return 0;
> > }
> > - mutex_lock(&gvt->lock);
> >
> > + mutex_lock(&gvt->lock);
> > if (atomic_read(&vgpu->gtt.n_write_protected_guest_page)) {
> > struct intel_vgpu_guest_page *gp;
> >
> > @@ -146,8 +145,7 @@ int intel_vgpu_emulate_mmio_read(struct intel_vgpu
> *vgpu, uint64_t pa,
> > ret, gp->gfn, pa, *(u32 *)p_data,
> > bytes);
> > }
> > - mutex_unlock(&gvt->lock);
> > - return ret;
> > + goto out;
> > }
> > }
> >
> > @@ -168,14 +166,12 @@ int intel_vgpu_emulate_mmio_read(struct
> intel_vgpu *vgpu, uint64_t pa,
> > p_data, bytes);
> > if (ret)
> > goto err;
> > - mutex_unlock(&gvt->lock);
> > - return ret;
> > + goto out;
> > }
> >
> > if (WARN_ON_ONCE(!reg_is_mmio(gvt, offset))) {
> > ret = intel_gvt_hypervisor_read_gpa(vgpu, pa, p_data, bytes);
> > - mutex_unlock(&gvt->lock);
> > - return ret;
> > + goto out;
> > }
> >
> > if (WARN_ON(!reg_is_mmio(gvt, offset + bytes - 1))) @@ -191,11
> > +187,13 @@ int intel_vgpu_emulate_mmio_read(struct intel_vgpu *vgpu,
> uint64_t pa,
> > goto err;
> >
> > intel_gvt_mmio_set_accessed(gvt, offset);
> > - mutex_unlock(&gvt->lock);
> > - return 0;
> > + ret = 0;
> > + goto out;
> > +
> > err:
> > gvt_vgpu_err("fail to emulate MMIO read %08x len %d\n",
> > offset, bytes);
> > +out:
> > mutex_unlock(&gvt->lock);
> > return ret;
> > }
>
> Please fix patch title as "drm/i915/gvt: xxx" and I think it's better we
> set error reason for each fail instead of using -EINVAL everywhere if
> someday we really need to check return fail reason, e.g
[Pei] sure, will change the title.
For the error reason, I agree that you are correct. But in this function, EINVAL is the default value of local parameter 'ret', it would get different values in different sub-function calls before calling 'goto'. For success case, the return value will be 0.
>
> diff --git a/drivers/gpu/drm/i915/gvt/mmio.c
> b/drivers/gpu/drm/i915/gvt/mmio.c index 4ea0feb5f04d..9759c247a65d
> 100644
> --- a/drivers/gpu/drm/i915/gvt/mmio.c
> +++ b/drivers/gpu/drm/i915/gvt/mmio.c
> @@ -155,19 +155,18 @@ int intel_vgpu_emulate_mmio_read(struct intel_vgpu
> *vgpu, uint64_t pa, {
> struct intel_gvt *gvt = vgpu->gvt;
> unsigned int offset = 0;
> - int ret = -EINVAL;
> -
> + int ret = 0;
>
> if (vgpu->failsafe) {
> failsafe_emulate_mmio_rw(vgpu, pa, p_data, bytes, true);
> return 0;
> }
> +
> mutex_lock(&gvt->lock);
>
> if (vgpu_gpa_is_aperture(vgpu, pa)) {
> ret = vgpu_aperture_rw(vgpu, pa, p_data, bytes, true);
> - mutex_unlock(&gvt->lock);
> - return ret;
> + goto out;
> }
>
> if (atomic_read(&vgpu->gtt.n_tracked_guest_page)) { @@ -183,56
> +182,56 @@ int intel_vgpu_emulate_mmio_read(struct intel_vgpu *vgpu,
> uint64_t pa,
> ret, t->gfn, pa, *(u32 *)p_data,
> bytes);
> }
> - mutex_unlock(&gvt->lock);
> - return ret;
> + goto out;
> }
> }
>
> offset = intel_vgpu_gpa_to_mmio_offset(vgpu, pa);
>
> - if (WARN_ON(bytes > 8))
> - goto err;
> + if (WARN_ON(bytes > 8)) {
> + ret = -EINVAL;
> + goto out;
> + }
>
> if (reg_is_gtt(gvt, offset)) {
> + ret = -EINVAL;
> if (WARN_ON(!IS_ALIGNED(offset, 4) && !IS_ALIGNED(offset, 8)))
> - goto err;
> + goto out;
> if (WARN_ON(bytes != 4 && bytes != 8))
> - goto err;
> + goto out;
> if (WARN_ON(!reg_is_gtt(gvt, offset + bytes - 1)))
> - goto err;
> + goto out;
>
> ret = intel_vgpu_emulate_gtt_mmio_read(vgpu, offset,
> p_data, bytes);
> - if (ret)
> - goto err;
> - mutex_unlock(&gvt->lock);
> - return ret;
> + goto out;
> }
>
> if (WARN_ON_ONCE(!reg_is_mmio(gvt, offset))) {
> ret = intel_gvt_hypervisor_read_gpa(vgpu, pa, p_data, bytes);
> - mutex_unlock(&gvt->lock);
> - return ret;
> + goto out;
> }
>
> - if (WARN_ON(!reg_is_mmio(gvt, offset + bytes - 1)))
> - goto err;
> + if (WARN_ON(!reg_is_mmio(gvt, offset + bytes - 1))) {
> + ret = -EFAULT;
> + goto out;
> + }
>
> if (!intel_gvt_mmio_is_unalign(gvt, offset)) {
> - if (WARN_ON(!IS_ALIGNED(offset, bytes)))
> - goto err;
> + if (WARN_ON(!IS_ALIGNED(offset, bytes))) {
> + ret = -EINVAL;
> + goto out;
> }
>
> ret = intel_vgpu_mmio_reg_rw(vgpu, offset, p_data, bytes, true);
> if (ret < 0)
> - goto err;
> + goto out;
>
> intel_gvt_mmio_set_accessed(gvt, offset);
> - mutex_unlock(&gvt->lock);
> - return 0;
> -err:
> - gvt_vgpu_err("fail to emulate MMIO read %08x len %d\n",
> - offset, bytes);
> +out:
> + if (ret)
> + gvt_vgpu_err("fail to emulate MMIO read %08x len %d\n",
> + offset, bytes);
> mutex_unlock(&gvt->lock);
> return ret;
> }
>
>
> --
> Open Source Technology Center, Intel ltd.
>
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