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Message-ID: <CA+ddPcOw5tP+rz7f6ty3HXyRUg1ReC_BwyhVpzuVVViZSwx_zg@mail.gmail.com>
Date: Mon, 5 Feb 2024 12:21:38 -0800
From: Jeffrey Kardatzke <jkardatzke@...gle.com>
To: "Jason-JH.Lin" <jason-jh.lin@...iatek.com>, Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
Chun-Kuang Hu <chunkuang.hu@...nel.org>, Jeffrey Kardatzke <jkardatzke@...gle.com>,
devicetree@...r.kernel.org, Project_Global_Chrome_Upstream_Group@...iatek.com,
Singo Chang <singo.chang@...iatek.com>, linux-kernel@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
Jason-ch Chen <jason-ch.chen@...iatek.com>, Nancy Lin <nancy.lin@...iatek.com>,
linux-mediatek@...ts.infradead.org, Shawn Sung <shawn.sung@...iatek.com>,
Johnson Wang <johnson.wang@...iatek.com>, linux-arm-kernel@...ts.infradead.org,
linux-media@...r.kernel.org
Subject: Re: [PATCH v3 03/11] drm/mediatek: Add secure buffer control flow to mtk_drm_gem
On Fri, Jan 12, 2024 at 5:13 AM Daniel Vetter <daniel@...ll.ch> wrote:
>
> On Sun, Dec 24, 2023 at 02:29:24AM +0800, Jason-JH.Lin wrote:
> > Add secure buffer control flow to mtk_drm_gem.
> >
> > When user space takes DRM_MTK_GEM_CREATE_ENCRYPTED flag and size
> > to create a mtk_drm_gem object, mtk_drm_gem will find a matched size
> > dma buffer from secure dma-heap and bind it to mtk_drm_gem object.
> >
> > Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
>
> Apologies for jumping rather late, but last year was a mess here.
>
> There's the fundamental issue that this is new uapi, and it needs open
> userspace, and I haven't seen that.
The open userspace for it is currently in minigbm for ChromeOS here:
https://chromium.googlesource.com/chromiumos/platform/minigbm/+/main/mediatek.c#322
Does that satisfy that particular requirement?
>
> What's more, this is a pure kms api so there's no precedent at all for
> adding special ioctl to those - all the existing support for
> protected/restricted content buffers in upstream has used render nodes and
> EGL_EXT_protected_content in mesa3d to enable this feature on the drm/kms
> side. So I'm not exactly sure what your plan here is, but you need one,
> and it needs to be more than a testcase/demo.
I'm probably not understanding something here, but for the Intel
protected content allocation there was a specific structure
(drm_i915_gem_create_ext_protected_content) added to the
DRM_IOCTL_I915_GEM_CREATE_EXT ioctl in order to enable allocation of
protected buffers. So wouldn't that be precedent for using an ioctl
like this to allocate a GEM object?
>
> The other issue, and the reason I've looked into the mtk code, is that the
> dma-buf implementation breaks the dma-buf api. So that needs to be
> changed.
Yeah, agreed here...I do see now that attaching dma_bufs for content
that is completely inaccessible by the kernel will be a no-go.
>
> Finally I think the primary way to display a protected content buffer on a
> pure kms driver should be by using prime fd2handle buffer importing.
> Because you're adding a dma-buf heap it's already possible for userspace
> to use this path (or at least try), and so we have to make this path work
> anyway.
Is what you're getting at here having MTK implement their own
gem_prime_import in order to work around having to do the dma_buf
attach operation? (from looking at the code, this appears to be the
only place in non-vendor specific code that dma_buf_attach is called)
>
> Once we have the prime import path working correctly for protected content
> buffers (which should shake out all the dma-api issues I've explained in
> the dma-buf heaps thread), it should be possible to implement the direct
> allocation function in a generic helper:
>
> struct drm_gem_object * drm_gem_create_object_from_heap(struct drm_device *dev,
> struct drm_file *file,
> struct drm_buf_heap *heap);
>
> Which does roughly:
>
> - allocate a dma-buf from the desired heap
> - import that dma-buf into the device using prime for the drm_file
> - using the already implemented driver import code for special cases like
> protected content buffers
>
> There should be no need to hand-roll all this code here, and especially
> not have any special-casing for the heap string name or things like that.
> That all must be handled in the dma-buf prime import code.
>
> Cheers, Sima
>
> > ---
> > drivers/gpu/drm/mediatek/mtk_drm_gem.c | 85 +++++++++++++++++++++++++-
> > drivers/gpu/drm/mediatek/mtk_drm_gem.h | 4 ++
> > 2 files changed, 88 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_gem.c b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> > index 30e347adcbe9..858f34a735f8 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> > @@ -4,6 +4,8 @@
> > */
> >
> > #include <linux/dma-buf.h>
> > +#include <linux/dma-heap.h>
> > +#include <uapi/linux/dma-heap.h>
> > #include <drm/mediatek_drm.h>
> >
> > #include <drm/drm.h>
> > @@ -55,6 +57,81 @@ static struct mtk_drm_gem_obj *mtk_drm_gem_init(struct drm_device *dev,
> > return mtk_gem_obj;
> > }
> >
> > +struct mtk_drm_gem_obj *mtk_drm_gem_create_from_heap(struct drm_device *dev,
> > + const char *heap, size_t size)
> > +{
> > + struct mtk_drm_private *priv = dev->dev_private;
> > + struct mtk_drm_gem_obj *mtk_gem;
> > + struct drm_gem_object *obj;
> > + struct dma_heap *dma_heap;
> > + struct dma_buf *dma_buf;
> > + struct dma_buf_attachment *attach;
> > + struct sg_table *sgt;
> > + struct iosys_map map = {};
> > + int ret;
> > +
> > + mtk_gem = mtk_drm_gem_init(dev, size);
> > + if (IS_ERR(mtk_gem))
> > + return ERR_CAST(mtk_gem);
> > +
> > + obj = &mtk_gem->base;
> > +
> > + dma_heap = dma_heap_find(heap);
> > + if (!dma_heap) {
> > + DRM_ERROR("heap find fail\n");
> > + goto err_gem_free;
> > + }
> > + dma_buf = dma_heap_buffer_alloc(dma_heap, size,
> > + O_RDWR | O_CLOEXEC, DMA_HEAP_VALID_HEAP_FLAGS);
> > + if (IS_ERR(dma_buf)) {
> > + DRM_ERROR("buffer alloc fail\n");
> > + dma_heap_put(dma_heap);
> > + goto err_gem_free;
> > + }
> > + dma_heap_put(dma_heap);
> > +
> > + attach = dma_buf_attach(dma_buf, priv->dma_dev);
> > + if (IS_ERR(attach)) {
> > + DRM_ERROR("attach fail, return\n");
> > + dma_buf_put(dma_buf);
> > + goto err_gem_free;
> > + }
> > +
> > + sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> > + if (IS_ERR(sgt)) {
> > + DRM_ERROR("map failed, detach and return\n");
> > + dma_buf_detach(dma_buf, attach);
> > + dma_buf_put(dma_buf);
> > + goto err_gem_free;
> > + }
> > + obj->import_attach = attach;
> > + mtk_gem->dma_addr = sg_dma_address(sgt->sgl);
> > + mtk_gem->sg = sgt;
> > + mtk_gem->size = dma_buf->size;
> > +
> > + if (!strcmp(heap, "mtk_svp") || !strcmp(heap, "mtk_svp_cma")) {
> > + /* secure buffer can not be mapped */
> > + mtk_gem->secure = true;
> > + } else {
> > + ret = dma_buf_vmap(dma_buf, &map);
> > + mtk_gem->kvaddr = map.vaddr;
> > + if (ret) {
> > + DRM_ERROR("map failed, ret=%d\n", ret);
> > + dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
> > + dma_buf_detach(dma_buf, attach);
> > + dma_buf_put(dma_buf);
> > + mtk_gem->kvaddr = NULL;
> > + }
> > + }
> > +
> > + return mtk_gem;
> > +
> > +err_gem_free:
> > + drm_gem_object_release(obj);
> > + kfree(mtk_gem);
> > + return ERR_PTR(-ENOMEM);
> > +}
> > +
> > struct mtk_drm_gem_obj *mtk_drm_gem_create(struct drm_device *dev,
> > size_t size, bool alloc_kmap)
> > {
> > @@ -225,7 +302,9 @@ struct drm_gem_object *mtk_gem_prime_import_sg_table(struct drm_device *dev,
> > if (IS_ERR(mtk_gem))
> > return ERR_CAST(mtk_gem);
> >
> > + mtk_gem->secure = !sg_page(sg->sgl);
> > mtk_gem->dma_addr = sg_dma_address(sg->sgl);
> > + mtk_gem->size = attach->dmabuf->size;
> > mtk_gem->sg = sg;
> >
> > return &mtk_gem->base;
> > @@ -301,7 +380,11 @@ int mtk_gem_create_ioctl(struct drm_device *dev, void *data,
> > struct drm_mtk_gem_create *args = data;
> > int ret;
> >
> > - mtk_gem = mtk_drm_gem_create(dev, args->size, false);
> > + if (args->flags & DRM_MTK_GEM_CREATE_ENCRYPTED)
> > + mtk_gem = mtk_drm_gem_create_from_heap(dev, "mtk_svp_cma", args->size);
> > + else
> > + mtk_gem = mtk_drm_gem_create(dev, args->size, false);
> > +
> > if (IS_ERR(mtk_gem))
> > return PTR_ERR(mtk_gem);
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_gem.h b/drivers/gpu/drm/mediatek/mtk_drm_gem.h
> > index 90f3d2916ec5..8fd5ce827d4f 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_drm_gem.h
> > +++ b/drivers/gpu/drm/mediatek/mtk_drm_gem.h
> > @@ -27,9 +27,11 @@ struct mtk_drm_gem_obj {
> > void *cookie;
> > void *kvaddr;
> > dma_addr_t dma_addr;
> > + size_t size;
> > unsigned long dma_attrs;
> > struct sg_table *sg;
> > struct page **pages;
> > + bool secure;
> > };
> >
> > #define to_mtk_gem_obj(x) container_of(x, struct mtk_drm_gem_obj, base)
> > @@ -37,6 +39,8 @@ struct mtk_drm_gem_obj {
> > void mtk_drm_gem_free_object(struct drm_gem_object *gem);
> > struct mtk_drm_gem_obj *mtk_drm_gem_create(struct drm_device *dev, size_t size,
> > bool alloc_kmap);
> > +struct mtk_drm_gem_obj *mtk_drm_gem_create_from_heap(struct drm_device *dev,
> > + const char *heap, size_t size);
> > int mtk_drm_gem_dumb_create(struct drm_file *file_priv, struct drm_device *dev,
> > struct drm_mode_create_dumb *args);
> > struct sg_table *mtk_gem_prime_get_sg_table(struct drm_gem_object *obj);
> > --
> > 2.18.0
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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