Caterina Shablia
2025-Jul-07 17:04 UTC
[PATCH v4 6/7] drm/gpuvm: Add DRM_GPUVA_REPEAT flag and logic
From: Asahi Lina <lina+kernel at asahilina.net>
To be able to support "fake sparse" mappings without relying on GPU
page
fault handling, drivers may need to create large (e.g. 4GiB) mappings of
the same page repeatedly (or same range of pages). Doing this through
individual mappings would be very wasteful. This can be handled better
by using a flag on map creation, but to do it safely, drm_gpuvm needs to
be aware of this special case.
Add a flag that signals that a given mapping is a page mapping, which is
repeated all over the entire requested VA range. This tweaks the
sm_map() logic to treat the GEM offsets differently when mappings are
a repeated ones so they are not incremented as they would be with regular
mappings.
The size of the GEM portion to repeat is passed through
drm_gpuva::gem::range. Most of the time it will be a page size, but
it can be bigger as long as it's less that drm_gpuva::va::range, and
drm_gpuva::gem::range is a multiple of drm_gpuva::va::range.
Signed-off-by: Asahi Lina <lina at asahilina.net>
Signed-off-by: Caterina Shablia <caterina.shablia at collabora.com>
---
drivers/gpu/drm/drm_gpuvm.c | 72 +++++++++++++++++++++++++++++++++----
include/drm/drm_gpuvm.h | 43 +++++++++++++++++++++-
2 files changed, 108 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c
index dd949a8853b0..817393596149 100644
--- a/drivers/gpu/drm/drm_gpuvm.c
+++ b/drivers/gpu/drm/drm_gpuvm.c
@@ -2063,6 +2063,7 @@ op_map_cb(const struct drm_gpuvm_ops *fn, void *priv,
op.map.va.range = req->va.range;
op.map.gem.obj = req->gem.obj;
op.map.gem.offset = req->gem.offset;
+ op.map.gem.range = req->gem.range;
op.map.flags = req->flags;
return fn->sm_step_map(&op, priv);
@@ -2122,12 +2123,53 @@ static bool can_merge(struct drm_gpuvm *gpuvm, const
struct drm_gpuva *a,
if (drm_WARN_ON(gpuvm->drm, b->va.addr > a->va.addr +
a->va.range))
return false;
+ if (a->flags & DRM_GPUVA_REPEAT) {
+ u64 va_diff = b->va.addr - a->va.addr;
+
+ /* If this is a repeated mapping, both the GEM range
+ * and offset must match.
+ */
+ if (a->gem.range != b->gem.range ||
+ a->gem.offset != b->gem.offset)
+ return false;
+
+ /* The difference between the VA addresses must be a
+ * multiple of the repeated range, otherwise there's
+ * a shift.
+ */
+ if (do_div(va_diff, a->gem.range))
+ return false;
+
+ return true;
+ }
+
/* We intentionally ignore u64 underflows because all we care about
* here is whether the VA diff matches the GEM offset diff.
*/
return b->va.addr - a->va.addr == b->gem.offset - a->gem.offset;
}
+static int check_map_req(struct drm_gpuvm *gpuvm,
+ const struct drm_gpuvm_map_req *req)
+{
+ if (unlikely(!drm_gpuvm_range_valid(gpuvm, req->va.addr,
req->va.range)))
+ return -EINVAL;
+
+ if (req->flags & DRM_GPUVA_REPEAT) {
+ u64 va_range = req->va.range;
+
+ /* For a repeated mapping, GEM range must be > 0
+ * and a multiple of the VA range.
+ */
+ if (unlikely(!req->gem.range ||
+ va_range < req->gem.range ||
+ do_div(va_range, req->gem.range)))
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int
__drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
const struct drm_gpuvm_ops *ops, void *priv,
@@ -2137,6 +2179,7 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
struct drm_gpuva reqva = {
.va.addr = req->va.addr,
.va.range = req->va.range,
+ .gem.range = req->gem.range,
.gem.offset = req->gem.offset,
.gem.obj = req->gem.obj,
.flags = req->flags,
@@ -2144,7 +2187,8 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
u64 req_end = req->va.addr + req->va.range;
int ret;
- if (unlikely(!drm_gpuvm_range_valid(gpuvm, req->va.addr,
req->va.range)))
+ ret = check_map_req(gpuvm, req);
+ if (unlikely(ret))
return -EINVAL;
drm_gpuvm_for_each_va_range_safe(va, next, gpuvm, req->va.addr, req_end) {
@@ -2175,7 +2219,8 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
.va.addr = req_end,
.va.range = range - req->va.range,
.gem.obj = obj,
- .gem.offset = offset + req->va.range,
+ .gem.range = va->gem.range,
+ .gem.offset = offset,
.flags = va->flags,
};
struct drm_gpuva_op_unmap u = {
@@ -2183,6 +2228,9 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
.keep = merge,
};
+ if (!(va->flags & DRM_GPUVA_REPEAT))
+ n.gem.offset += req->va.range;
+
ret = op_remap_cb(ops, priv, NULL, &n, &u);
if (ret)
return ret;
@@ -2194,6 +2242,7 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
.va.addr = addr,
.va.range = ls_range,
.gem.obj = obj,
+ .gem.range = va->gem.range,
.gem.offset = offset,
.flags = va->flags,
};
@@ -2220,11 +2269,14 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
.va.addr = req_end,
.va.range = end - req_end,
.gem.obj = obj,
- .gem.offset = offset + ls_range +
- req->va.range,
+ .gem.range = va->gem.range,
+ .gem.offset = offset,
.flags = va->flags,
};
+ if (!(va->flags & DRM_GPUVA_REPEAT))
+ n.gem.offset += ls_range + req->va.range;
+
ret = op_remap_cb(ops, priv, &p, &n, &u);
if (ret)
return ret;
@@ -2250,7 +2302,8 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
.va.addr = req_end,
.va.range = end - req_end,
.gem.obj = obj,
- .gem.offset = offset + req_end - addr,
+ .gem.range = va->gem.range,
+ .gem.offset = offset,
.flags = va->flags,
};
struct drm_gpuva_op_unmap u = {
@@ -2258,6 +2311,9 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
.keep = merge,
};
+ if (!(va->flags & DRM_GPUVA_REPEAT))
+ n.gem.offset += req_end - addr;
+
ret = op_remap_cb(ops, priv, NULL, &n, &u);
if (ret)
return ret;
@@ -2294,6 +2350,7 @@ __drm_gpuvm_sm_unmap(struct drm_gpuvm *gpuvm,
prev.va.addr = addr;
prev.va.range = req_addr - addr;
prev.gem.obj = obj;
+ prev.gem.range = va->gem.range;
prev.gem.offset = offset;
prev.flags = va->flags;
@@ -2304,7 +2361,10 @@ __drm_gpuvm_sm_unmap(struct drm_gpuvm *gpuvm,
next.va.addr = req_end;
next.va.range = end - req_end;
next.gem.obj = obj;
- next.gem.offset = offset + (req_end - addr);
+ prev.gem.range = va->gem.range;
+ next.gem.offset = offset;
+ if (!(va->flags & DRM_GPUVA_REPEAT))
+ next.gem.offset += req_end - addr;
next.flags = va->flags;
next_split = true;
diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
index f77a89e791f1..629e8508f99f 100644
--- a/include/drm/drm_gpuvm.h
+++ b/include/drm/drm_gpuvm.h
@@ -56,10 +56,19 @@ enum drm_gpuva_flags {
*/
DRM_GPUVA_SPARSE = (1 << 1),
+ /**
+ * @DRM_GPUVA_REPEAT:
+ *
+ * Flag indicating that the &drm_gpuva is a mapping of a GEM
+ * portion repeated multiple times to fill the virtual address
+ * range.
+ */
+ DRM_GPUVA_REPEAT = (1 << 2),
+
/**
* @DRM_GPUVA_USERBITS: user defined bits
*/
- DRM_GPUVA_USERBITS = (1 << 2),
+ DRM_GPUVA_USERBITS = (1 << 3),
};
/**
@@ -111,6 +120,18 @@ struct drm_gpuva {
*/
u64 offset;
+ /*
+ * @gem.range: the range of the GEM that is mapped
+ *
+ * When dealing with normal mappings, this must be zero.
+ * When flags has DRM_GPUVA_REPEAT set, this field must be
+ * smaller than va.range and va.range must be a multiple of
+ * gem.range.
+ * This is a u32 not a u64 because we expect repeated mappings
+ * to be pointing to relatively small portions of a GEM object.
+ */
+ u32 range;
+
/**
* @gem.obj: the mapped &drm_gem_object
*/
@@ -842,6 +863,17 @@ struct drm_gpuva_op_map {
*/
u64 offset;
+ /*
+ * @gem.range: the range of the GEM that is mapped
+ *
+ * When dealing with normal mappings, this must be zero.
+ * When flags has DRM_GPUVA_REPEAT set, it must be smaller
+ * and be a multiple of va.range. This is a u32 not a u64
+ * because we expect repeated mappings to be pointing to
+ * a relatively small portion of a GEM object.
+ */
+ u32 range;
+
/**
* @gem.obj: the &drm_gem_object to map
*/
@@ -1078,6 +1110,15 @@ struct drm_gpuvm_map_req {
/** @offset: offset in the GEM */
u64 offset;
+
+ /**
+ * @range: size of the range of the GEM object to map
+ *
+ * Must be zero unless flags has DRM_GPUVA_REPEAT set.
+ * If DRM_GPUVA_REPEAT is set, this field must be less than va.range,
+ * and va.range must be a multiple of gem.range.
+ */
+ u32 range;
} gem;
/** @flags: combination of DRM_GPUVA_ flags describing the mapping properties.
*/
--
2.47.2
Danilo Krummrich
2025-Jul-07 19:33 UTC
[PATCH v4 6/7] drm/gpuvm: Add DRM_GPUVA_REPEAT flag and logic
On Mon Jul 7, 2025 at 7:04 PM CEST, Caterina Shablia wrote:> From: Asahi Lina <lina+kernel at asahilina.net> > > To be able to support "fake sparse" mappings without relying on GPU page > fault handling, drivers may need to create large (e.g. 4GiB) mappings of > the same page repeatedly (or same range of pages). Doing this through > individual mappings would be very wasteful. This can be handled better > by using a flag on map creation, but to do it safely, drm_gpuvm needs to > be aware of this special case. > > Add a flag that signals that a given mapping is a page mapping, which is > repeated all over the entire requested VA range. This tweaks the > sm_map() logic to treat the GEM offsets differently when mappings are > a repeated ones so they are not incremented as they would be with regular > mappings. > > The size of the GEM portion to repeat is passed through > drm_gpuva::gem::range. Most of the time it will be a page size, but > it can be bigger as long as it's less that drm_gpuva::va::range, and > drm_gpuva::gem::range is a multiple of drm_gpuva::va::range.Should be "as long as it's less that drm_gpuva::va::range, and drm_gpuva::va::range is a multiple of drm_gpuva::gem::range". I also think this feature deserves its own section in the global GPUVM documentation -- please add a corresponding paragraph.> +static int check_map_req(struct drm_gpuvm *gpuvm,Let's call this validate_map_request().> + const struct drm_gpuvm_map_req *req) > +{ > + if (unlikely(!drm_gpuvm_range_valid(gpuvm, req->va.addr, req->va.range))) > + return -EINVAL; > + > + if (req->flags & DRM_GPUVA_REPEAT) { > + u64 va_range = req->va.range; > + > + /* For a repeated mapping, GEM range must be > 0 > + * and a multiple of the VA range. > + */ > + if (unlikely(!req->gem.range || > + va_range < req->gem.range || > + do_div(va_range, req->gem.range))) > + return -EINVAL; > + } > + > + return 0; > +} > + > static int > __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > const struct drm_gpuvm_ops *ops, void *priv, > @@ -2137,6 +2179,7 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > struct drm_gpuva reqva = { > .va.addr = req->va.addr, > .va.range = req->va.range, > + .gem.range = req->gem.range, > .gem.offset = req->gem.offset, > .gem.obj = req->gem.obj, > .flags = req->flags, > @@ -2144,7 +2187,8 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > u64 req_end = req->va.addr + req->va.range; > int ret; > > - if (unlikely(!drm_gpuvm_range_valid(gpuvm, req->va.addr, req->va.range))) > + ret = check_map_req(gpuvm, req); > + if (unlikely(ret)) > return -EINVAL; > > drm_gpuvm_for_each_va_range_safe(va, next, gpuvm, req->va.addr, req_end) { > @@ -2175,7 +2219,8 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > .va.addr = req_end, > .va.range = range - req->va.range, > .gem.obj = obj, > - .gem.offset = offset + req->va.range, > + .gem.range = va->gem.range, > + .gem.offset = offset,Why change this from offset + req->va.range to just offset? Same for similar other changes below. Also it seems that we need to update the documentation which shows all potential cases when calling __drm_gpuvm_sm_map() [1]. [1] https://docs.kernel.org/gpu/drm-mm.html#split-and-merge> .flags = va->flags, > }; > struct drm_gpuva_op_unmap u = { > @@ -2183,6 +2228,9 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > .keep = merge, > }; > > + if (!(va->flags & DRM_GPUVA_REPEAT)) > + n.gem.offset += req->va.range; > + > ret = op_remap_cb(ops, priv, NULL, &n, &u); > if (ret) > return ret; > @@ -2194,6 +2242,7 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > .va.addr = addr, > .va.range = ls_range, > .gem.obj = obj, > + .gem.range = va->gem.range, > .gem.offset = offset, > .flags = va->flags, > }; > @@ -2220,11 +2269,14 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > .va.addr = req_end, > .va.range = end - req_end, > .gem.obj = obj, > - .gem.offset = offset + ls_range + > - req->va.range, > + .gem.range = va->gem.range, > + .gem.offset = offset, > .flags = va->flags, > }; > > + if (!(va->flags & DRM_GPUVA_REPEAT)) > + n.gem.offset += ls_range + req->va.range; > + > ret = op_remap_cb(ops, priv, &p, &n, &u); > if (ret) > return ret; > @@ -2250,7 +2302,8 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > .va.addr = req_end, > .va.range = end - req_end, > .gem.obj = obj, > - .gem.offset = offset + req_end - addr, > + .gem.range = va->gem.range, > + .gem.offset = offset, > .flags = va->flags, > }; > struct drm_gpuva_op_unmap u = { > @@ -2258,6 +2311,9 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, > .keep = merge, > }; > > + if (!(va->flags & DRM_GPUVA_REPEAT)) > + n.gem.offset += req_end - addr; > + > ret = op_remap_cb(ops, priv, NULL, &n, &u); > if (ret) > return ret; > @@ -2294,6 +2350,7 @@ __drm_gpuvm_sm_unmap(struct drm_gpuvm *gpuvm, > prev.va.addr = addr; > prev.va.range = req_addr - addr; > prev.gem.obj = obj; > + prev.gem.range = va->gem.range; > prev.gem.offset = offset; > prev.flags = va->flags; > > @@ -2304,7 +2361,10 @@ __drm_gpuvm_sm_unmap(struct drm_gpuvm *gpuvm, > next.va.addr = req_end; > next.va.range = end - req_end; > next.gem.obj = obj; > - next.gem.offset = offset + (req_end - addr); > + prev.gem.range = va->gem.range; > + next.gem.offset = offset; > + if (!(va->flags & DRM_GPUVA_REPEAT)) > + next.gem.offset += req_end - addr; > next.flags = va->flags; > > next_split = true; > diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h > index f77a89e791f1..629e8508f99f 100644 > --- a/include/drm/drm_gpuvm.h > +++ b/include/drm/drm_gpuvm.h > @@ -56,10 +56,19 @@ enum drm_gpuva_flags { > */ > DRM_GPUVA_SPARSE = (1 << 1), > > + /** > + * @DRM_GPUVA_REPEAT: > + * > + * Flag indicating that the &drm_gpuva is a mapping of a GEM > + * portion repeated multiple times to fill the virtual address"of a GEM object with a certain range that is repeated multiple times to ..."