|
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: Question about xen and Rasp 4B
On Sat, 30 Jan 2021, Julien Grall wrote: > > > On 27/01/2021 11:47, Jukka Kaartinen wrote: > > > > > > > > > > > > On Tue, Jan 26, 2021 at 10:22 PM Stefano Stabellini > > > > <sstabellini@xxxxxxxxxx <mailto:sstabellini@xxxxxxxxxx>> wrote: > > > > > > > > On Tue, 26 Jan 2021, Jukka Kaartinen wrote: > > > > > On Tue, Jan 26, 2021 at 2:54 AM Stefano Stabellini > > > > <sstabellini@xxxxxxxxxx <mailto:sstabellini@xxxxxxxxxx>> wrote: > > > > > On Sat, 23 Jan 2021, Jukka Kaartinen wrote: > > > > > > Thanks for the response! > > > > > > > > > > > > On Sat, Jan 23, 2021 at 2:27 AM Stefano Stabellini > > > > <sstabellini@xxxxxxxxxx <mailto:sstabellini@xxxxxxxxxx>> wrote: > > > > > > + xen-devel, Roman, > > > > > > > > > > > > > > > > > > On Fri, 22 Jan 2021, Jukka Kaartinen wrote: > > > > > > > Hi Stefano, > > > > > > > I'm Jukka Kaartinen a SW developer working on > > > > enabling hypervisors on mobile platforms. One of our HW that we use > > > > on > > > > > > development is > > > > > > > Raspberry Pi 4B. I wonder if you could help me a > > > > bit :). > > > > > > > > > > > > > > I'm trying to enable the GPU with Xen + Raspberry > > > > Pi for > > > > > > dom0. > > > > https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=232323#p1797605 > > > > <https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=232323#p1797605> > > > > > > > > > > > > > > > > > > I got so far that GPU drivers are loaded (v3d & > > > > vc4) without errors. But now Xen returns error when X is starting: > > > > > > > (XEN) traps.c:1986:d0v1 HSR=0x93880045 > > > > pc=0x00007f97b14e70 gva=0x7f7f817000 gpa=0x0000401315d000 > > > > > > > I tried to debug what causes this and looks > > > > like find_mmio_handler cannot find handler. > > > > > > > (See more here: > > > > https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=232323&start=25#p1801691 > > > > > > > > <https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=232323&start=25#p1801691> > > > > > > > > ) > > > > > > > > > > > > > > Any ideas why the handler is not found? > > > > > > > > > > > > > > > > > > Hi Jukka, > > > > > > > > > > > > I am glad to hear that you are interested in Xen on > > > > RaspberryPi :-) I > > > > > > haven't tried the GPU yet, I have been using the > > > > serial only. > > > > > > Roman, did you ever get the GPU working? > > > > > > > > > > > > > > > > > > The error is a data abort error: Linux is trying to > > > > access an address > > > > > > which is not mapped to dom0. The address seems to > > > > be 0x401315d000. It is > > > > > > a pretty high address; I looked in device tree but > > > > couldn't spot it. > > > > > > > > > > > > >From the HSR (the syndrom register) it looks like > > > > it is a translation > > > > > > fault at EL1 on stage1. As if the Linux address > > > > mapping was wrong. > > > > > > Anyone has any ideas how this could happen? Maybe a > > > > reserved-memory > > > > > > misconfiguration? > > > > > > > > > > > > I had issues with loading the driver in the first place. > > > > Apparently swiotlb is used, maybe it can cause this. I also tried to > > > > > enable CMA. > > > > > > config.txt: > > > > > > dtoverlay=vc4-fkms-v3d,cma=320M@0x0-0x40000000 > > > > > > gpu_mem=128 > > > > > > > > > > Also looking at your other reply and the implementation of > > > > > vc4_bo_create, it looks like this is a CMA problem. > > > > > > > > > > It would be good to run a test with the swiotlb-xen > > > > disabled: > > > > > > > > > > diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c > > > > > index 467fa225c3d0..2bdd12785d14 100644 > > > > > --- a/arch/arm/xen/mm.c > > > > > +++ b/arch/arm/xen/mm.c > > > > > @@ -138,8 +138,7 @@ void > > > > xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int > > > > order) > > > > > static int __init xen_mm_init(void) > > > > > { > > > > > struct gnttab_cache_flush cflush; > > > > > - if (!xen_initial_domain()) > > > > > - return 0; > > > > > + return 0; > > > > > xen_swiotlb_init(1, false); > > > > > > > > > > cflush.op = 0; > > > > > > > > > > With this change the kernel is not booting up. (btw. I'm using > > > > USB SSD for my OS.) > > > > > [ 0.071081] bcm2835-dma fe007000.dma: Unable to set DMA mask > > > > > [ 0.076277] bcm2835-dma fe007b00.dma: Unable to set DMA mask > > > > > (XEN) physdev.c:16:d0v0 PHYSDEVOP cmd=25: not implemented > > > > > (XEN) physdev.c:16:d0v0 PHYSDEVOP cmd=15: not implemented > > > > > [ 0.592695] pci 0000:00:00.0: Failed to add - passthrough or > > > > MSI/MSI-X might fail! > > > > > (XEN) physdev.c:16:d0v0 PHYSDEVOP cmd=15: not implemented > > > > > [ 0.606819] pci 0000:01:00.0: Failed to add - passthrough or > > > > MSI/MSI-X might fail! > > > > > [ 1.212820] usb 1-1: device descriptor read/64, error 18 > > > > > [ 1.452815] usb 1-1: device descriptor read/64, error 18 > > > > > [ 1.820813] usb 1-1: device descriptor read/64, error 18 > > > > > [ 2.060815] usb 1-1: device descriptor read/64, error 18 > > > > > [ 2.845548] usb 1-1: device descriptor read/8, error -61 > > > > > [ 2.977603] usb 1-1: device descriptor read/8, error -61 > > > > > [ 3.237530] usb 1-1: device descriptor read/8, error -61 > > > > > [ 3.369585] usb 1-1: device descriptor read/8, error -61 > > > > > [ 3.480765] usb usb1-port1: unable to enumerate USB device > > > > > > > > > > Traces stop here. I could try with a memory card. Maybe it makes > > > > a difference. > > > > > > > > This is very surprising. Disabling swiotlb-xen should make things > > > > better > > > > not worse. The only reason I can think of why it could make things > > > > worse > > > > is if Linux runs out of low memory. Julien's patch > > > > 437b0aa06a014ce174e24c0d3530b3e9ab19b18b for Xen should have > > > > addressed > > > > that issue though. Julien, any ideas? > > > > > > I think, Stefano's small patch is not enough to disable the swiotlb as we > > > will still override the DMA ops. You also likely want: > > > > > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > > > index 8a8949174b1c..aa43e249ecdd 100644 > > > --- a/arch/arm/mm/dma-mapping.c > > > +++ b/arch/arm/mm/dma-mapping.c > > > @@ -2279,7 +2279,7 @@ void arch_setup_dma_ops(struct device *dev, u64 > > > dma_base, u64 size, > > > set_dma_ops(dev, dma_ops); > > > > > > #ifdef CONFIG_XEN > > > - if (xen_initial_domain()) > > > + if (0 || xen_initial_domain()) > > > dev->dma_ops = &xen_swiotlb_dma_ops; > > > #endif > > > dev->archdata.dma_ops_setup = true; > > > > > > Otherwise, you would still use the swiotlb DMA ops that would not be > > > functional as we disabled the swiotlb. > > > > > > This would explain the following error because it will check whether the > > > mask is valid using the callback dma_supported(): > > > > > > [ 0.071081] bcm2835-dma fe007000.dma: Unable to set DMA mask > > > > > Good catch. > > GPU works now and I can start X! Thanks! I was also able to create domU that > > runs Raspian OS. > > Glad to hear it works! IIRC, the swiotlb may become necessary when running > guest if the guest memory ends up to be used for DMA transaction. It is necessary if you are using PV network or PV disk: memory shared by another domU could end up being used in a DMA transaction. For that, you need swiotlb-xen. > > Now that swiotlb is disabled what does it mean? > > I can see two reasons: > 1) You have limited memory below the 30 bits mark. So Swiotlb and CMA may > try to fight for the low memory. > 2) We found a few conversion bugs in the swiotlb on RPI4 last year (IIRC the > DMA and physical address may be different). I looked at the Linux branch you > are using and they seem to all be there. So there might be another bug. > > I am not sure how to figure out where is the problem. Stefano, do you have a > suggestion where to start? Both 1) and 2) are possible. It is also possible that another driver, probably something related to CMA or DRM, has some special dma_ops handling that doesn't work well together with swiotlb-xen. Given that the original error seemed to be related to vc4_bo_create, which calls dma_alloc_wc, I would add a couple of printks to xen_swiotlb_alloc_coherent to help us figure it out: diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index 2b385c1b4a99..cac8b09af603 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -295,6 +295,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size, /* Convert the size to actually allocated. */ size = 1UL << (order + XEN_PAGE_SHIFT); + printk("DEBUG %s %d size=%lu flags=%lx attr=%lx\n",__func__,__LINE__,size,flags,attrs); /* On ARM this function returns an ioremap'ped virtual address for * which virt_to_phys doesn't return the corresponding physical * address. In fact on ARM virt_to_phys only works for kernel direct @@ -315,16 +316,20 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size, phys = dma_to_phys(hwdev, *dma_handle); dev_addr = xen_phys_to_dma(hwdev, phys); if (((dev_addr + size - 1 <= dma_mask)) && - !range_straddles_page_boundary(phys, size)) + !range_straddles_page_boundary(phys, size)) { *dma_handle = dev_addr; - else { + printk("DEBUG %s %d phys=%lx dma=%lx\n",__func__,__LINE__,phys,dev_addr); + } else { if (xen_create_contiguous_region(phys, order, fls64(dma_mask), dma_handle) != 0) { + printk("DEBUG %s %d\n",__func__,__LINE__); xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs); return NULL; } *dma_handle = phys_to_dma(hwdev, *dma_handle); SetPageXenRemapped(virt_to_page(ret)); + printk("DEBUG %s %d dma_mask=%d page_boundary=%d phys=%lx dma=%lx\n",__func__,__LINE__, + ((dev_addr + size - 1 <= dma_mask)),range_straddles_page_boundary(phys, size),phys,*dma_handle); } memset(ret, 0, size); return ret; > > And also can I pass the GPU to domU? Raspberry Pi 4 is limited HW and > > doesn't have IOMMU. I'm trying to create similar OS like QubesOS where GPU, > > Network, keyboard/mouse, ... are isolated to their own VMs. > > Without an IOMMU or any other HW mechamisns (e.g. MPU), it would not be safe > to assign a DMA-capable device to a non-trusted VM. > > If you trust the VM where you assigned a device, then a possible approach > would be to have the VM direct mapped (e.g. guest physical address == host > physical address). Although, I can foreese some issues if you have multiple > VMs requires memory below 30 bits (there seem to be limited amount)> > > If you don't trust the VM where you assigned a device, then your best option > will be to expose a PV interface of the device and have your backend > sanitizing the request and issuing it on behalf of the guest. FYI you could do that with the existing PVFB drivers that only support 2D graphics.
|
 |
Lists.xenproject.org is hosted with RackSpace, monitoring our |