[PATCH] drm/i915/gvt: Support BAR0 qword access

[Zhenyu Wang]

On 2017.12.15 09:03:50 +0000, Zhang, Tina wrote:
> > Your patch will get qword pci config r/w which isn't allowed in our code.
> It won't touch pci configuration space, only BAR0.
> And the reason why we need this patch is that it can make dma-buf display stable during guest booting up.

Could you elaborate on the problem?

This makes me recall https://lists.freedesktop.org/archives/intel-gvt-dev/2017-August/001578.html,
and how about the concern from that thread?

> > > -----Original Message-----
> > > From: intel-gvt-dev
> > > [mailto:intel-gvt-dev-bounces at lists.freedesktop.org] On Behalf Of Tina
> > > Zhang
> > > Sent: Friday, December 15, 2017 4:44 PM
> > > Cc: Yuan, Hang <hang.yuan at intel.com>;
> > > intel-gvt-dev at lists.freedesktop.org;
> > > Wang, Zhi A <zhi.a.wang at intel.com>; Zhenyu Wang
> > > <zhenyuw at linux.intel.com>; Zhang, Tina <tina.zhang at intel.com>
> > > Subject: [PATCH] drm/i915/gvt: Support BAR0 qword access
> > >
> > > GGTT is in BAR0 with qword aligned. With a qemu patch (commit:
> > > 38d49e8c1523d97d2191190d3f7b4ce7a0ab5aa3), VFIO can use 8-byte
> > reads/
> > > writes to access it.
> > >
> > > This patch is to enable BAR0 to support the qword accessing.
> > >
> > > This patch can also remove some error log about "vfio_pin_pages failed"
> > > which cased by partial updating GGTT entry.
> > >
> > > Signed-off-by: Tina Zhang <tina.zhang at intel.com>
> > > Cc: Zhenyu Wang <zhenyuw at linux.intel.com>
> > > Cc: Zhi Wang <zhi.a.wang at intel.com>
> > > Cc: Hang Yuan <hang.yuan at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/gvt/kvmgt.c | 32
> > > ++++++++++++++++++++++++++++++--
> > >  1 file changed, 30 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c
> > > b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > > index b8a85e0..4f7c0d7 100644
> > > --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> > > +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > > @@ -705,12 +705,26 @@ static ssize_t intel_vgpu_read(struct
> > > mdev_device *mdev, char __user *buf,
> > >  			size_t count, loff_t *ppos)
> > >  {
> > >  	unsigned int done = 0;
> > > +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> > >  	int ret;
> > >
> > >  	while (count) {
> > >  		size_t filled;
> > >
> > > -		if (count >= 4 && !(*ppos % 4)) {
> > > +		if (count >= 8 && !(*ppos % 8) &&
> > > +		    (index == VFIO_PCI_BAR0_REGION_INDEX)) {
> > > +			u64 val;
> > > +
> > > +			ret = intel_vgpu_rw(mdev, (char *)&val, sizeof(val),
> > > +					ppos, false);
> > > +			if (ret <= 0)
> > > +				goto read_err;
> > > +
> > > +			if (copy_to_user(buf, &val, sizeof(val)))
> > > +				goto read_err;
> > > +
> > > +			filled = 8;
> > > +		} else if (count >= 4 && !(*ppos % 4)) {
> > >  			u32 val;
> > >
> > >  			ret = intel_vgpu_rw(mdev, (char *)&val, sizeof(val),
> > @@
> > > -765,12 +779,26 @@ static ssize_t intel_vgpu_write(struct mdev_device
> > > *mdev,
> > >  				size_t count, loff_t *ppos)
> > >  {
> > >  	unsigned int done = 0;
> > > +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> > >  	int ret;
> > >
> > >  	while (count) {
> > >  		size_t filled;
> > >
> > > -		if (count >= 4 && !(*ppos % 4)) {
> > > +		if (count >= 8 && !(*ppos % 8) &&
> > > +		    (index == VFIO_PCI_BAR0_REGION_INDEX)) {
> > > +			u64 val;
> > > +
> > > +			if (copy_from_user(&val, buf, sizeof(val)))
> > > +				goto write_err;
> > > +
> > > +			ret = intel_vgpu_rw(mdev, (char *)&val, sizeof(val),
> > > +					ppos, true);
> > > +			if (ret <= 0)
> > > +				goto write_err;
> > > +
> > > +			filled = 8;
> > > +		} else if (count >= 4 && !(*ppos % 4)) {
> > >  			u32 val;
> > >
> > >  			if (copy_from_user(&val, buf, sizeof(val)))
> > > --
> > > 2.7.4
> > >
> > > _______________________________________________
> > > intel-gvt-dev mailing list
> > > intel-gvt-dev at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev
> _______________________________________________
> intel-gvt-dev mailing list
> intel-gvt-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

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