| Message ID | 20230123093102.12392-1-m.szyprowski@samsung.com |
|---|---|
| State | New |
| Headers | show |
| Series | iommu/exynos: add missing set_platform_dma_ops callback | expand |
Hi, I'm sorry for a delay in replying, but I was busy with other stuff. On 23.01.2023 22:00, Jason Gunthorpe wrote: > On Mon, Jan 23, 2023 at 10:31:01AM +0100, Marek Szyprowski wrote: >> Add set_platform_dma_ops() required for proper driver operation on ARM >> 32bit arch after recent changes in the IOMMU framework (detach ops >> removal). > Thanks for looking into this! > > Can you explain more about how this actually solves the problem in the > commit message? I don't get it. Exynos DRM driver calls arm_iommu_detach_device(), then arm_iommu_attach_device() with a difrent 'mapping', see drivers/gpu/drm/exynos/exynos_drm_dma.c Lack of set_platform_dma_ops leads to a warning in iommu_group_do_set_platform_dma(). The other case of calling arm_iommu_detach_device() is after unsuccessful probe of the platform device. >> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c >> index 6fc58e89712f..c4955d045855 100644 >> --- a/drivers/iommu/exynos-iommu.c >> +++ b/drivers/iommu/exynos-iommu.c >> @@ -1346,8 +1346,10 @@ static void exynos_iommu_release_device(struct device *dev) >> struct iommu_group *group = iommu_group_get(dev); >> >> if (group) { >> +#ifndef CONFIG_ARM >> WARN_ON(owner->domain != >> iommu_group_default_domain(group)); >> +#endif >> exynos_iommu_detach_device(owner->domain, dev); >> iommu_group_put(group); >> } >> @@ -1398,6 +1400,9 @@ static int exynos_iommu_of_xlate(struct device *dev, >> static const struct iommu_ops exynos_iommu_ops = { >> .domain_alloc = exynos_iommu_domain_alloc, >> .device_group = generic_device_group, >> +#ifdef CONFIG_ARM >> + .set_platform_dma_ops = exynos_iommu_release_device, >> +#endif > This is ugly, if you need a set_platform_dma_ops it should not be > called release... Release is supposed to be about putting the HW back > to some idle state because we are unplugging the struct device. Indeed this patch was a bit ugly, I've did it in a bit of hurry. That time I've simply checked how it is implemented in other drivers and found that it very similar to the release operation, so I did it in exynos-iommu that way. I've checked again and indeed there are some differences, so I will send a fix in a few minutes. Best regards
On Fri, Feb 17, 2023 at 12:08:42PM +0100, Marek Szyprowski wrote: > Hi, > > I'm sorry for a delay in replying, but I was busy with other stuff. > > On 23.01.2023 22:00, Jason Gunthorpe wrote: > > On Mon, Jan 23, 2023 at 10:31:01AM +0100, Marek Szyprowski wrote: > >> Add set_platform_dma_ops() required for proper driver operation on ARM > >> 32bit arch after recent changes in the IOMMU framework (detach ops > >> removal). > > Thanks for looking into this! > > > > Can you explain more about how this actually solves the problem in the > > commit message? I don't get it. > > Exynos DRM driver calls arm_iommu_detach_device(), then > arm_iommu_attach_device() with a difrent 'mapping', see > drivers/gpu/drm/exynos/exynos_drm_dma.c Lack of set_platform_dma_ops > leads to a warning in iommu_group_do_set_platform_dma(). The other case > of calling arm_iommu_detach_device() is after unsuccessful probe of the > platform device. Why can't this just use the normal iommu path in all cases? It looks like it is trying to copy the DMA API domain from a parent device to a sub device. Even when using arm_iommu an iommu_domain is still present, so the copy code should work? Though I'm still not really sure how this arm_iommu stuff works.. eg if a driver does iommu_device_claim_dma_owner() how does the iommu_domain get set back to the arm_iommu's mapping's iommu_domain? According to the API that is what set_platform is supposed to do (eg it is what s390 does), but I don't see any code like that in any of the ARM32 drivers.. Jason
On 2023-02-17 12:35, Jason Gunthorpe wrote: > On Fri, Feb 17, 2023 at 12:08:42PM +0100, Marek Szyprowski wrote: >> Hi, >> >> I'm sorry for a delay in replying, but I was busy with other stuff. >> >> On 23.01.2023 22:00, Jason Gunthorpe wrote: >>> On Mon, Jan 23, 2023 at 10:31:01AM +0100, Marek Szyprowski wrote: >>>> Add set_platform_dma_ops() required for proper driver operation on ARM >>>> 32bit arch after recent changes in the IOMMU framework (detach ops >>>> removal). >>> Thanks for looking into this! >>> >>> Can you explain more about how this actually solves the problem in the >>> commit message? I don't get it. >> >> Exynos DRM driver calls arm_iommu_detach_device(), then >> arm_iommu_attach_device() with a difrent 'mapping', see >> drivers/gpu/drm/exynos/exynos_drm_dma.c Lack of set_platform_dma_ops >> leads to a warning in iommu_group_do_set_platform_dma(). The other case >> of calling arm_iommu_detach_device() is after unsuccessful probe of the >> platform device. > > Why can't this just use the normal iommu path in all cases? > > It looks like it is trying to copy the DMA API domain from a parent > device to a sub device. > > Even when using arm_iommu an iommu_domain is still present, so the > copy code should work? The ARM DMA domain is a regular unmanaged domain owned by the ARM DMA code - in order to use any *other* domain, a user has to detach from that first (wrapped up in arm_iommu_detach_device() which also swizzles the DMA ops at the same time). Without set_platform_dma, that detach is now impossible (because no IOMMU API default domain exists either). > Though I'm still not really sure how this arm_iommu stuff works.. > > eg if a driver does iommu_device_claim_dma_owner() how does the > iommu_domain get set back to the arm_iommu's mapping's iommu_domain? It doesn't. Fact is that VFIO has only ever worked on Arm with arm-smmu and its old deprecated DT bindings which don't interact with any of the DMA ops stuff. And ownership has always been inherently enforced here since the DMA ops are just another external user from the IOMMU API's PoV. > According to the API that is what set_platform is supposed to do (eg > it is what s390 does), but I don't see any code like that in any of > the ARM32 drivers.. As above, it's in the relevant users, not the drivers. For what you're thinking of, the "platform" state is only ever transient. (for the purposes of this discussion, ignore the MTK and Renesas drivers bodging around to implement pseudo-default-domain support on *top* of the user-centric arm_iommu_* APIs; that's a whole other mess to unravel) Thanks, Robin.
On Mon, Feb 20, 2023 at 01:58:40PM +0000, Robin Murphy wrote: > On 2023-02-17 12:35, Jason Gunthorpe wrote: > > On Fri, Feb 17, 2023 at 12:08:42PM +0100, Marek Szyprowski wrote: > > > Hi, > > > > > > I'm sorry for a delay in replying, but I was busy with other stuff. > > > > > > On 23.01.2023 22:00, Jason Gunthorpe wrote: > > > > On Mon, Jan 23, 2023 at 10:31:01AM +0100, Marek Szyprowski wrote: > > > > > Add set_platform_dma_ops() required for proper driver operation on ARM > > > > > 32bit arch after recent changes in the IOMMU framework (detach ops > > > > > removal). > > > > Thanks for looking into this! > > > > > > > > Can you explain more about how this actually solves the problem in the > > > > commit message? I don't get it. > > > > > > Exynos DRM driver calls arm_iommu_detach_device(), then > > > arm_iommu_attach_device() with a difrent 'mapping', see > > > drivers/gpu/drm/exynos/exynos_drm_dma.c Lack of set_platform_dma_ops > > > leads to a warning in iommu_group_do_set_platform_dma(). The other case > > > of calling arm_iommu_detach_device() is after unsuccessful probe of the > > > platform device. > > > > Why can't this just use the normal iommu path in all cases? > > > > It looks like it is trying to copy the DMA API domain from a parent > > device to a sub device. > > > > Even when using arm_iommu an iommu_domain is still present, so the > > copy code should work? > > The ARM DMA domain is a regular unmanaged domain owned by the ARM DMA code - > in order to use any *other* domain, a user has to detach from that first > (wrapped up in arm_iommu_detach_device() which also swizzles the DMA ops at > the same time). Without set_platform_dma, that detach is now impossible > (because no IOMMU API default domain exists either). I was looking at this again, and for completeness, the reason it doesn't have a default_domain is a bit subtle. The driver does support IOMMU_DOMAIN_DMA, and it will go through all the iommu_group_alloc_default_domain() stuff with that.. But... __iommu_domain_alloc() calls iommu_get_dma_cookie() which will be wired to fail on ARM32, so the core code nixes the IOMMU_DOMAIN_DMA after the driver successfully created it. I wonder if that is actually what we want? As it seems like it would be OK for ARM32 to have, effectively, a permanently empty unmanaged domain as the default_domain? If instead of failing due to iommu_get_dma_cookie() we set the type to UNMANAGED and make that the default domain it could fix all of this, even for all the other ARM32 drivers that haven't reported this yet? Alternatively since we taught these drivers to support IDENTITY, we should be able to remove the set_platform_dma_ops and instead implement for ARM32 def_domain_type fixed to return IDENTITY? Jason
On 07.04.2023 01:37, Jason Gunthorpe wrote: > On Mon, Feb 20, 2023 at 01:58:40PM +0000, Robin Murphy wrote: >> On 2023-02-17 12:35, Jason Gunthorpe wrote: >>> On Fri, Feb 17, 2023 at 12:08:42PM +0100, Marek Szyprowski wrote: >>>> I'm sorry for a delay in replying, but I was busy with other stuff. >>>> >>>> On 23.01.2023 22:00, Jason Gunthorpe wrote: >>>>> On Mon, Jan 23, 2023 at 10:31:01AM +0100, Marek Szyprowski wrote: >>>>>> Add set_platform_dma_ops() required for proper driver operation on ARM >>>>>> 32bit arch after recent changes in the IOMMU framework (detach ops >>>>>> removal). >>>>> Thanks for looking into this! >>>>> >>>>> Can you explain more about how this actually solves the problem in the >>>>> commit message? I don't get it. >>>> Exynos DRM driver calls arm_iommu_detach_device(), then >>>> arm_iommu_attach_device() with a difrent 'mapping', see >>>> drivers/gpu/drm/exynos/exynos_drm_dma.c Lack of set_platform_dma_ops >>>> leads to a warning in iommu_group_do_set_platform_dma(). The other case >>>> of calling arm_iommu_detach_device() is after unsuccessful probe of the >>>> platform device. >>> Why can't this just use the normal iommu path in all cases? >>> >>> It looks like it is trying to copy the DMA API domain from a parent >>> device to a sub device. >>> >>> Even when using arm_iommu an iommu_domain is still present, so the >>> copy code should work? >> The ARM DMA domain is a regular unmanaged domain owned by the ARM DMA code - >> in order to use any *other* domain, a user has to detach from that first >> (wrapped up in arm_iommu_detach_device() which also swizzles the DMA ops at >> the same time). Without set_platform_dma, that detach is now impossible >> (because no IOMMU API default domain exists either). > I was looking at this again, and for completeness, the reason it > doesn't have a default_domain is a bit subtle. > > The driver does support IOMMU_DOMAIN_DMA, and it will go through all > the iommu_group_alloc_default_domain() stuff with that.. > > But... __iommu_domain_alloc() calls iommu_get_dma_cookie() which will > be wired to fail on ARM32, so the core code nixes the IOMMU_DOMAIN_DMA > after the driver successfully created it. > > I wonder if that is actually what we want? As it seems like it would > be OK for ARM32 to have, effectively, a permanently empty unmanaged > domain as the default_domain? > > If instead of failing due to iommu_get_dma_cookie() we set the type to > UNMANAGED and make that the default domain it could fix all of this, > even for all the other ARM32 drivers that haven't reported this yet? > > Alternatively since we taught these drivers to support IDENTITY, we > should be able to remove the set_platform_dma_ops and instead > implement for ARM32 def_domain_type fixed to return IDENTITY? Maybe it would be easier to simply switch ARM32 to generic IOMMU-DMA layer? Best regards
On Thu, Apr 13, 2023 at 12:03:55AM +0200, Marek Szyprowski wrote: > On 07.04.2023 01:37, Jason Gunthorpe wrote: > > On Mon, Feb 20, 2023 at 01:58:40PM +0000, Robin Murphy wrote: > >> On 2023-02-17 12:35, Jason Gunthorpe wrote: > >>> On Fri, Feb 17, 2023 at 12:08:42PM +0100, Marek Szyprowski wrote: > >>>> I'm sorry for a delay in replying, but I was busy with other stuff. > >>>> > >>>> On 23.01.2023 22:00, Jason Gunthorpe wrote: > >>>>> On Mon, Jan 23, 2023 at 10:31:01AM +0100, Marek Szyprowski wrote: > >>>>>> Add set_platform_dma_ops() required for proper driver operation on ARM > >>>>>> 32bit arch after recent changes in the IOMMU framework (detach ops > >>>>>> removal). > >>>>> Thanks for looking into this! > >>>>> > >>>>> Can you explain more about how this actually solves the problem in the > >>>>> commit message? I don't get it. > >>>> Exynos DRM driver calls arm_iommu_detach_device(), then > >>>> arm_iommu_attach_device() with a difrent 'mapping', see > >>>> drivers/gpu/drm/exynos/exynos_drm_dma.c Lack of set_platform_dma_ops > >>>> leads to a warning in iommu_group_do_set_platform_dma(). The other case > >>>> of calling arm_iommu_detach_device() is after unsuccessful probe of the > >>>> platform device. > >>> Why can't this just use the normal iommu path in all cases? > >>> > >>> It looks like it is trying to copy the DMA API domain from a parent > >>> device to a sub device. > >>> > >>> Even when using arm_iommu an iommu_domain is still present, so the > >>> copy code should work? > >> The ARM DMA domain is a regular unmanaged domain owned by the ARM DMA code - > >> in order to use any *other* domain, a user has to detach from that first > >> (wrapped up in arm_iommu_detach_device() which also swizzles the DMA ops at > >> the same time). Without set_platform_dma, that detach is now impossible > >> (because no IOMMU API default domain exists either). > > I was looking at this again, and for completeness, the reason it > > doesn't have a default_domain is a bit subtle. > > > > The driver does support IOMMU_DOMAIN_DMA, and it will go through all > > the iommu_group_alloc_default_domain() stuff with that.. > > > > But... __iommu_domain_alloc() calls iommu_get_dma_cookie() which will > > be wired to fail on ARM32, so the core code nixes the IOMMU_DOMAIN_DMA > > after the driver successfully created it. > > > > I wonder if that is actually what we want? As it seems like it would > > be OK for ARM32 to have, effectively, a permanently empty unmanaged > > domain as the default_domain? > > > > If instead of failing due to iommu_get_dma_cookie() we set the type to > > UNMANAGED and make that the default domain it could fix all of this, > > even for all the other ARM32 drivers that haven't reported this yet? > > > > Alternatively since we taught these drivers to support IDENTITY, we > > should be able to remove the set_platform_dma_ops and instead > > implement for ARM32 def_domain_type fixed to return IDENTITY? > > Maybe it would be easier to simply switch ARM32 to generic IOMMU-DMA layer? It is the long term goal, yes In the short term it would be nice if we could at least keep the hacks out of the drivers Jason
diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c index 6fc58e89712f..c4955d045855 100644 --- a/drivers/iommu/exynos-iommu.c +++ b/drivers/iommu/exynos-iommu.c @@ -1346,8 +1346,10 @@ static void exynos_iommu_release_device(struct device *dev) struct iommu_group *group = iommu_group_get(dev); if (group) { +#ifndef CONFIG_ARM WARN_ON(owner->domain != iommu_group_default_domain(group)); +#endif exynos_iommu_detach_device(owner->domain, dev); iommu_group_put(group); } @@ -1398,6 +1400,9 @@ static int exynos_iommu_of_xlate(struct device *dev, static const struct iommu_ops exynos_iommu_ops = { .domain_alloc = exynos_iommu_domain_alloc, .device_group = generic_device_group, +#ifdef CONFIG_ARM + .set_platform_dma_ops = exynos_iommu_release_device, +#endif .probe_device = exynos_iommu_probe_device, .release_device = exynos_iommu_release_device, .pgsize_bitmap = SECT_SIZE | LPAGE_SIZE | SPAGE_SIZE,
Add set_platform_dma_ops() required for proper driver operation on ARM 32bit arch after recent changes in the IOMMU framework (detach ops removal). Fixes: c1fe9119ee70 ("iommu: Add set_platform_dma_ops callbacks") Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- drivers/iommu/exynos-iommu.c | 5 +++++ 1 file changed, 5 insertions(+)