On Fri, 29 Jun 2018 14:12:41 +1000 David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Jun 26, 2018 at 03:59:26PM +1000, Alexey Kardashevskiy wrote: > > We already have a check in drivers/vfio/vfio_iommu_spapr_tce.c that > > an IOMMU page is contained in the physical page so the PCI hardware won't > > get access to unassigned host memory. > > > > However we do not have this check in KVM fastpath (H_PUT_TCE accelerated > > code) so the user space can pin memory backed with 64k pages and create > > a hardware TCE table with a bigger page size. We were lucky so far and > > did not hit this yet as the very first time the mapping happens > > we do not have tbl::it_userspace allocated yet and fall back to > > the userspace which in turn calls VFIO IOMMU driver and that fails > > because of the check in vfio_iommu_spapr_tce.c which is really > > sustainable solution. > > > > This stores the smallest preregistered page size in the preregistered > > region descriptor and changes the mm_iommu_xxx API to check this against > > the IOMMU page size. > > > > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx> > > --- > > Changes: > > v2: > > * explicitly check for compound pages before calling compound_order() > > > > --- > > The bug is: run QEMU _without_ hugepages (no -mempath) and tell it to > > advertise 16MB pages to the guest; a typical pseries guest will use 16MB > > for IOMMU pages without checking the mmu pagesize and this will fail > > at https://git.qemu.org/?p=qemu.git;a=blob;f=hw/vfio/common.c;h=fb396cf00ac40eb35967a04c9cc798ca896eed57;hb=refs/heads/master#l256 > > > > With the change, mapping will fail in KVM and the guest will print: > > > > mlx5_core 0000:00:00.0: ibm,create-pe-dma-window(2027) 0 8000000 20000000 18 1f returned 0 (liobn = 0x80000001 starting addr = 8000000 0) > > mlx5_core 0000:00:00.0: created tce table LIOBN 0x80000001 for /pci@800000020000000/ethernet@0 > > mlx5_core 0000:00:00.0: failed to map direct window for > > /pci@800000020000000/ethernet@0: -1 > > [snip] > > @@ -124,7 +125,7 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries, > > struct mm_iommu_table_group_mem_t **pmem) > > { > > struct mm_iommu_table_group_mem_t *mem; > > - long i, j, ret = 0, locked_entries = 0; > > + long i, j, ret = 0, locked_entries = 0, pageshift; > > struct page *page = NULL; > > > > mutex_lock(&mem_list_mutex); > > @@ -166,6 +167,8 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries, > > goto unlock_exit; > > } > > > > + mem->pageshift = 30; /* start from 1G pages - the biggest we have */ > > What about 16G pages on an HPT system? Below in the loop mem->pageshift will reduce to the biggest actual size which will be 16mb/64k/4k. Or remain 1GB if no memory is actually pinned, no loss there. > > > for (i = 0; i < entries; ++i) { > > if (1 != get_user_pages_fast(ua + (i << PAGE_SHIFT), > > 1/* pages */, 1/* iswrite */, &page)) { > > @@ -199,6 +202,11 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries, > > } > > } > > populate: > > + pageshift = PAGE_SHIFT; > > + if (PageCompound(page)) > > + pageshift += compound_order(compound_head(page)); > > + mem->pageshift = min_t(unsigned int, mem->pageshift, pageshift); > > Why not make mem->pageshift and pageshift local the same type to avoid > the min_t() ? I was under impression min() is deprecated (misinterpret checkpatch.pl may be) and therefore did not pay attention to it. I can fix this and repost if there is no other question. > > > + > > mem->hpas[i] = page_to_pfn(page) << PAGE_SHIFT; > > } > > > > @@ -349,7 +357,7 @@ struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm, > > EXPORT_SYMBOL_GPL(mm_iommu_find); > > > > long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem, > > - unsigned long ua, unsigned long *hpa) > > + unsigned long ua, unsigned int pageshift, unsigned long *hpa) > > { > > const long entry = (ua - mem->ua) >> PAGE_SHIFT; > > u64 *va = &mem->hpas[entry]; > > @@ -357,6 +365,9 @@ long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem, > > if (entry >= mem->entries) > > return -EFAULT; > > > > + if (pageshift > mem->pageshift) > > + return -EFAULT; > > + > > *hpa = *va | (ua & ~PAGE_MASK); > > > > return 0; > > @@ -364,7 +375,7 @@ long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem, > > EXPORT_SYMBOL_GPL(mm_iommu_ua_to_hpa); > > > > long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_group_mem_t *mem, > > - unsigned long ua, unsigned long *hpa) > > + unsigned long ua, unsigned int pageshift, unsigned long *hpa) > > { > > const long entry = (ua - mem->ua) >> PAGE_SHIFT; > > void *va = &mem->hpas[entry]; > > @@ -373,6 +384,9 @@ long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_group_mem_t *mem, > > if (entry >= mem->entries) > > return -EFAULT; > > > > + if (pageshift > mem->pageshift) > > + return -EFAULT; > > + > > pa = (void *) vmalloc_to_phys(va); > > if (!pa) > > return -EFAULT; > > diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c > > index 2da5f05..7cd63b0 100644 > > --- a/drivers/vfio/vfio_iommu_spapr_tce.c > > +++ b/drivers/vfio/vfio_iommu_spapr_tce.c > > @@ -467,7 +467,7 @@ static int tce_iommu_prereg_ua_to_hpa(struct tce_container *container, > > if (!mem) > > return -EINVAL; > > > > - ret = mm_iommu_ua_to_hpa(mem, tce, phpa); > > + ret = mm_iommu_ua_to_hpa(mem, tce, shift, phpa); > > if (ret) > > return -EINVAL; > > -- Alexey
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