Hi Alex, On 8/25/25 6:15 PM, Alex Williamson wrote: > On Mon, 25 Aug 2025 13:48:59 +0000 > Pranjal Shrivastava <praan@xxxxxxxxxx> wrote: > >> On Wed, Aug 20, 2025 at 08:25:47PM +0000, Mostafa Saleh wrote: >>> Hi Eric, >>> >>> On Wed, Aug 20, 2025 at 06:29:27PM +0200, Eric Auger wrote: >>>> Hi Mostafa, >>>> >>>> On 8/20/25 5:20 PM, Mostafa Saleh wrote: >>>>> Hi Eric, >>>>> >>>>> On Tue, Aug 19, 2025 at 11:58:32AM +0200, Eric Auger wrote: >>>>>> Hi Mostafa, >>>>>> >>>>>> On 8/18/25 7:33 PM, Mostafa Saleh wrote: >>>>>>> On Mon, Aug 18, 2025 at 10:52:42AM -0600, Alex Williamson wrote: >>>>>>>> On Fri, 15 Aug 2025 16:59:37 +0000 >>>>>>>> Mostafa Saleh <smostafa@xxxxxxxxxx> wrote: >>>>>>>> >>>>>>>>> Hi Alex, >>>>>>>>> >>>>>>>>> On Wed, Aug 06, 2025 at 11:03:12AM -0600, Alex Williamson wrote: >>>>>>>>>> vfio-platform hasn't had a meaningful contribution in years. In-tree >>>>>>>>>> hardware support is predominantly only for devices which are long since >>>>>>>>>> e-waste. QEMU support for platform devices is slated for removal in >>>>>>>>>> QEMU-10.2. Eric Auger presented on the future of the vfio-platform >>>>>>>>>> driver and difficulties supporting new devices at KVM Forum 2024, >>>>>>>>>> gaining some support for removal, some disagreement, but garnering no >>>>>>>>>> new hardware support, leaving the driver in a state where it cannot >>>>>>>>>> be tested. >>>>>>>>>> >>>>>>>>>> Mark as obsolete and subject to removal. >>>>>>>>> Recently(this year) in Android, we enabled VFIO-platform for protected KVM, >>>>>>>>> and it’s supported in our VMM (CrosVM) [1]. >>>>>>>>> CrosVM support is different from Qemu, as it doesn't require any device >>>>>>>>> specific logic in the VMM, however, it relies on loading a device tree >>>>>>>>> template in runtime (with “compatiable” string...) and it will just >>>>>>>>> override regs, irqs.. So it doesn’t need device knowledge (at least for now) >>>>>>>>> Similarly, the kernel doesn’t need reset drivers as the hypervisor handles that. >>>>>>>> I think what we attempt to achieve in vfio is repeatability and data >>>>>>>> integrity independent of the hypervisor. IOW, if we 'kill -9' the >>>>>>>> hypervisor process, the kernel can bring the device back to a default >>>>>>>> state where the device isn't wedged or leaking information through the >>>>>>>> device to the next use case. If the hypervisor wants to support >>>>>>>> enhanced resets on top of that, that's great, but I think it becomes >>>>>>>> difficult to argue that vfio-platform itself holds up its end of the >>>>>>>> bargain if we're really trusting the hypervisor to handle these aspects. >>>>>>> Sorry I was not clear, we only use that in Android for ARM64 and pKVM, >>>>>>> where the hypervisor in this context means the code running in EL2 which >>>>>>> is more privileged than the kernel, so it should be trusted. >>>>>>> However, as I mentioned that code is not upstream yet, so it's a valid >>>>>>> concern that the kernel still needs a reset driver. >>>>>>> >>>>>>>>> Unfortunately, there is no upstream support at the moment, we are making >>>>>>>>> some -slow- progress on that [2][3] >>>>>>>>> >>>>>>>>> If it helps, I have access to HW that can run that and I can review/test >>>>>>>>> changes, until upstream support lands; if you are open to keeping VFIO-platform. >>>>>>>>> Or I can look into adding support for existing upstream HW(with platforms I am >>>>>>>>> familiar with as Pixel-6) >>>>>>>> Ultimately I'll lean on Eric to make the call. I know he's concerned >>>>>>>> about testing, but he raised that and various other concerns whether >>>>>>>> platform device really have a future with vfio nearly a year ago and >>>>>>>> nothing has changed. Currently it requires a module option opt-in to >>>>>>>> enable devices that the kernel doesn't know how to reset. Is that >>>>>>>> sufficient or should use of such a device taint the kernel? If any >>>>>>>> device beyond the few e-waste devices that we know how to reset taint >>>>>>>> the kernel, should this support really even be in the kernel? Thanks, >>>>>>> I think with the way it’s supported at the moment we need the kernel >>>>>>> to ensure that reset happens. >>>>>> Effectively my main concern is I cannot test vfio-platform anymore. We >>>>>> had some CVEs also impacting the vfio platform code base and it is a >>>>>> major issue not being able to test. That's why I was obliged, last year, >>>>>> to resume the integration of a new device (the tegra234 mgbe), nobody >>>>>> seemed to be really interested in and this work could not be upstreamed >>>>>> due to lack of traction and its hacky nature. >>>>>> >>>>>> You did not really comment on which kind of devices were currently >>>>>> integrated. Are they within the original scope of vfio (with DMA >>>>>> capabilities and protected by an IOMMU)? Last discussion we had in >>>>>> https://lore.kernel.org/all/ZvvLpLUZnj-Z_tEs@xxxxxxxxxx/ led to the >>>>>> conclusion that maybe VFIO was not the best suited framework. >>>>> At the moment, Android device assignement only supports DMA capable >>>>> devices which are behind an IOMMU, and we use VFIO-platform for that, >>>>> most of our use cases are accelerators. >>>>> >>>>> In that thread, I was looking into adding support for simpler devices >>>>> (such as sensors) but as discussed that won’t be done through >>>>> VFIO-platform. >>>>> >>>>> Ignoring Android, as I mentioned, I can work on adding support for >>>>> existing upstream platforms (preferably ARM64, that I can get access to) >>>>> such as Pixel-6, which should make it easier to test. >>>>> >>>>> Also, we have some interest on adding new features such as run-time >>>>> power management. >>>> OK fair enough. If Alex agrees then we can wait for those efforts. Also >>>> I think it would make sense to formalize the way you reset the devices >>>> (I understand the hyp does that under the hood). >>> I think currently - with some help from the platform bus- we can rely on >>> the existing shutdown method, instead of specific hooks. >>> As the hypervisor logic will only be for ARM64 (at least for now), I can >>> look more into this. >>> >>> But I think the top priority would be to establish a decent platform to >>> test with, I will start looking into Pixel-6 (although that would need >>> to land IOMMU support for it upstream first). I also have a morello >>> board with SMMUv3, but I think it's all PCI. >>> >>>>> >>>>>> In case we keep the driver in, I think we need to get a garantee that >>>>>> you or someone else at Google commits to review and test potential >>>>>> changes with a perspective to take over its maintenance. >>>>> I can’t make guarantees on behalf of Google, but I can contribute in >>>>> reviewing/testing/maintenance of the driver as far as I am able to. >>>>> If you want, you can add me as reviewer to the driver. >>>> I understand. I think the usual way then is for you to send a patch to >>>> update the Maintainers file. >>> I see, I will send one shortly. >>> >> I could contribute time to help with the maintenance effort here, if >> needed. Please let me know if you'd like that. > You can join Mostafa and post a patch to be added as a designated > reviewer. > > If we're not going to deprecate vfio-platform overall for now, what > about vfio-amba and all the reset drivers? It seems that even if > Google cares about vfio-platform, these still fall outside of what's > being used or tested. Should we drive something like below to see what > comes out of the woodwork?: As far as I know vfio-amba has never been used. With regards to the reset driver I think this is reasonable to deprecate them as the HW has ewasted Thanks Eric > > diff --git a/drivers/vfio/platform/Kconfig b/drivers/vfio/platform/Kconfig > index 88fcde51f024..c6be29b2c24b 100644 > --- a/drivers/vfio/platform/Kconfig > +++ b/drivers/vfio/platform/Kconfig > @@ -17,10 +17,13 @@ config VFIO_PLATFORM > If you don't know what to do here, say N. > > config VFIO_AMBA > - tristate "VFIO support for AMBA devices" > + tristate "VFIO support for AMBA devices (DEPRECATED)" > depends on ARM_AMBA || COMPILE_TEST > select VFIO_PLATFORM_BASE > help > + The vfio-amba driver is deprecated and will be removed in a > + future kernel release. > + > Support for ARM AMBA devices with VFIO. This is required to make > use of ARM AMBA devices present on the system using the VFIO > framework. > diff --git a/drivers/vfio/platform/reset/Kconfig b/drivers/vfio/platform/reset/Kconfig > index dcc08dc145a5..70af0dbe293b 100644 > --- a/drivers/vfio/platform/reset/Kconfig > +++ b/drivers/vfio/platform/reset/Kconfig > @@ -1,21 +1,21 @@ > # SPDX-License-Identifier: GPL-2.0-only > if VFIO_PLATFORM > config VFIO_PLATFORM_CALXEDAXGMAC_RESET > - tristate "VFIO support for calxeda xgmac reset" > + tristate "VFIO support for calxeda xgmac reset (DEPRECATED)" > help > Enables the VFIO platform driver to handle reset for Calxeda xgmac > > If you don't know what to do here, say N. > > config VFIO_PLATFORM_AMDXGBE_RESET > - tristate "VFIO support for AMD XGBE reset" > + tristate "VFIO support for AMD XGBE reset (DEPRECATED)" > help > Enables the VFIO platform driver to handle reset for AMD XGBE > > If you don't know what to do here, say N. > > config VFIO_PLATFORM_BCMFLEXRM_RESET > - tristate "VFIO support for Broadcom FlexRM reset" > + tristate "VFIO support for Broadcom FlexRM reset (DEPRECATED)" > depends on ARCH_BCM_IPROC || COMPILE_TEST > default ARCH_BCM_IPROC > help > diff --git a/drivers/vfio/platform/reset/vfio_platform_amdxgbe.c b/drivers/vfio/platform/reset/vfio_platform_amdxgbe.c > index abdca900802d..45f386a042a9 100644 > --- a/drivers/vfio/platform/reset/vfio_platform_amdxgbe.c > +++ b/drivers/vfio/platform/reset/vfio_platform_amdxgbe.c > @@ -52,6 +52,8 @@ static int vfio_platform_amdxgbe_reset(struct vfio_platform_device *vdev) > u32 dma_mr_value, pcs_value, value; > unsigned int count; > > + dev_err_once(vdev->device, "DEPRECATION: VFIO AMD XGBE platform reset is deprecated and will be removed in a future kernel release\n"); > + > if (!xgmac_regs->ioaddr) { > xgmac_regs->ioaddr = > ioremap(xgmac_regs->addr, xgmac_regs->size); > diff --git a/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c b/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c > index 1131ebe4837d..51c9d156f307 100644 > --- a/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c > +++ b/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c > @@ -72,6 +72,8 @@ static int vfio_platform_bcmflexrm_reset(struct vfio_platform_device *vdev) > int rc = 0, ret = 0, ring_num = 0; > struct vfio_platform_region *reg = &vdev->regions[0]; > > + dev_err_once(vdev->device, "DEPRECATION: VFIO Broadcom FlexRM platform reset is deprecated and will be removed in a future kernel release\n"); > + > /* Map FlexRM ring registers if not mapped */ > if (!reg->ioaddr) { > reg->ioaddr = ioremap(reg->addr, reg->size); > diff --git a/drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c b/drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c > index 63cc7f0b2e4a..a298045a8e19 100644 > --- a/drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c > +++ b/drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c > @@ -50,6 +50,8 @@ static int vfio_platform_calxedaxgmac_reset(struct vfio_platform_device *vdev) > { > struct vfio_platform_region *reg = &vdev->regions[0]; > > + dev_err_once(vdev->device, "DEPRECATION: VFIO Calxeda xgmac platform reset is deprecated and will be removed in a future kernel release\n"); > + > if (!reg->ioaddr) { > reg->ioaddr = > ioremap(reg->addr, reg->size); > diff --git a/drivers/vfio/platform/vfio_amba.c b/drivers/vfio/platform/vfio_amba.c > index ff8ff8480968..9f5c527baa8a 100644 > --- a/drivers/vfio/platform/vfio_amba.c > +++ b/drivers/vfio/platform/vfio_amba.c > @@ -70,6 +70,8 @@ static int vfio_amba_probe(struct amba_device *adev, const struct amba_id *id) > struct vfio_platform_device *vdev; > int ret; > > + dev_err_once(&adev->dev, "DEPRECATION: vfio-amba is deprecated and will be removed in a future kernel release\n"); > + > vdev = vfio_alloc_device(vfio_platform_device, vdev, &adev->dev, > &vfio_amba_ops); > if (IS_ERR(vdev)) >
