| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Tue, 18 May 2021 12:58:31 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Shenming Lu <lushenming@...wei.com>
Cc: Cornelia Huck <cohuck@...hat.com>, Will Deacon <will@...nel.org>,
Robin Murphy <robin.murphy@....com>,
Joerg Roedel <joro@...tes.org>,
Jean-Philippe Brucker <jean-philippe@...aro.org>,
Eric Auger <eric.auger@...hat.com>, <kvm@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<iommu@...ts.linux-foundation.org>, <linux-api@...r.kernel.org>,
Kevin Tian <kevin.tian@...el.com>,
Lu Baolu <baolu.lu@...ux.intel.com>, <yi.l.liu@...el.com>,
Christoph Hellwig <hch@...radead.org>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Barry Song <song.bao.hua@...ilicon.com>,
<wanghaibin.wang@...wei.com>, <yuzenghui@...wei.com>
Subject: Re: [RFC PATCH v3 3/8] vfio/type1: Add an MMU notifier to avoid
pinning
On Fri, 9 Apr 2021 11:44:15 +0800
Shenming Lu <lushenming@...wei.com> wrote:
> To avoid pinning pages when they are mapped in IOMMU page tables, we
> add an MMU notifier to tell the addresses which are no longer valid
> and try to unmap them.
>
> Signed-off-by: Shenming Lu <lushenming@...wei.com>
> ---
> drivers/vfio/vfio_iommu_type1.c | 112 +++++++++++++++++++++++++++++++-
> 1 file changed, 109 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index ab0ff60ee207..1cb9d1f2717b 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -40,6 +40,7 @@
> #include <linux/notifier.h>
> #include <linux/dma-iommu.h>
> #include <linux/irqdomain.h>
> +#include <linux/mmu_notifier.h>
>
> #define DRIVER_VERSION "0.2"
> #define DRIVER_AUTHOR "Alex Williamson <alex.williamson@...hat.com>"
> @@ -69,6 +70,7 @@ struct vfio_iommu {
> struct mutex lock;
> struct rb_root dma_list;
> struct blocking_notifier_head notifier;
> + struct mmu_notifier mn;
> unsigned int dma_avail;
> unsigned int vaddr_invalid_count;
> uint64_t pgsize_bitmap;
> @@ -1204,6 +1206,72 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
> return unlocked;
> }
>
> +/* Unmap the IOPF mapped pages in the specified range. */
> +static void vfio_unmap_partial_iopf(struct vfio_iommu *iommu,
> + struct vfio_dma *dma,
> + dma_addr_t start, dma_addr_t end)
> +{
> + struct iommu_iotlb_gather *gathers;
> + struct vfio_domain *d;
> + int i, num_domains = 0;
> +
> + list_for_each_entry(d, &iommu->domain_list, next)
> + num_domains++;
> +
> + gathers = kzalloc(sizeof(*gathers) * num_domains, GFP_KERNEL);
> + if (gathers) {
> + for (i = 0; i < num_domains; i++)
> + iommu_iotlb_gather_init(&gathers[i]);
> + }
If we're always serialized on iommu->lock, would it make sense to have
gathers pre-allocated on the vfio_iommu object?
> +
> + while (start < end) {
> + unsigned long bit_offset;
> + size_t len;
> +
> + bit_offset = (start - dma->iova) >> PAGE_SHIFT;
> +
> + for (len = 0; start + len < end; len += PAGE_SIZE) {
> + if (!IOPF_MAPPED_BITMAP_GET(dma,
> + bit_offset + (len >> PAGE_SHIFT)))
> + break;
There are bitmap helpers for this, find_first_bit(),
find_next_zero_bit().
> + }
> +
> + if (len) {
> + i = 0;
> + list_for_each_entry(d, &iommu->domain_list, next) {
> + size_t unmapped;
> +
> + if (gathers)
> + unmapped = iommu_unmap_fast(d->domain,
> + start, len,
> + &gathers[i++]);
> + else
> + unmapped = iommu_unmap(d->domain,
> + start, len);
> +
> + if (WARN_ON(unmapped != len))
The IOMMU API does not guarantee arbitrary unmap sizes, this will
trigger and this exit path is wrong. If we've already unmapped the
IOMMU, shouldn't we proceed with @unmapped rather than @len so the
device can re-fault the extra mappings? Otherwise the IOMMU state
doesn't match the iopf bitmap state.
> + goto out;
> + }
> +
> + bitmap_clear(dma->iopf_mapped_bitmap,
> + bit_offset, len >> PAGE_SHIFT);
> +
> + cond_resched();
> + }
> +
> + start += (len + PAGE_SIZE);
> + }
> +
> +out:
> + if (gathers) {
> + i = 0;
> + list_for_each_entry(d, &iommu->domain_list, next)
> + iommu_iotlb_sync(d->domain, &gathers[i++]);
> +
> + kfree(gathers);
> + }
> +}
> +
> static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
> {
> WARN_ON(!RB_EMPTY_ROOT(&dma->pfn_list));
> @@ -3197,17 +3265,18 @@ static int vfio_iommu_type1_dma_map_iopf(struct iommu_fault *fault, void *data)
>
> vaddr = iova - dma->iova + dma->vaddr;
>
> - if (vfio_pin_page_external(dma, vaddr, &pfn, true))
> + if (vfio_pin_page_external(dma, vaddr, &pfn, false))
> goto out_invalid;
>
> if (vfio_iommu_map(iommu, iova, pfn, 1, dma->prot)) {
> - if (put_pfn(pfn, dma->prot))
> - vfio_lock_acct(dma, -1, true);
> + put_pfn(pfn, dma->prot);
> goto out_invalid;
> }
>
> bitmap_set(dma->iopf_mapped_bitmap, bit_offset, 1);
>
> + put_pfn(pfn, dma->prot);
> +
> out_success:
> status = IOMMU_PAGE_RESP_SUCCESS;
>
> @@ -3220,6 +3289,43 @@ static int vfio_iommu_type1_dma_map_iopf(struct iommu_fault *fault, void *data)
> return 0;
> }
>
> +static void mn_invalidate_range(struct mmu_notifier *mn, struct mm_struct *mm,
> + unsigned long start, unsigned long end)
> +{
> + struct vfio_iommu *iommu = container_of(mn, struct vfio_iommu, mn);
> + struct rb_node *n;
> + int ret;
> +
> + mutex_lock(&iommu->lock);
> +
> + ret = vfio_wait_all_valid(iommu);
> + if (WARN_ON(ret < 0))
> + return;
Is WARN_ON sufficient for this error condition? We've been told to
evacuate a range of mm, the device still has DMA access, we've removed
page pinning. This seems like a BUG_ON condition to me, we can't allow
the system to continue in any way with pages getting unmapped from
under the device.
> +
> + for (n = rb_first(&iommu->dma_list); n; n = rb_next(n)) {
> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> + unsigned long start_n, end_n;
> +
> + if (end <= dma->vaddr || start >= dma->vaddr + dma->size)
> + continue;
> +
> + start_n = ALIGN_DOWN(max_t(unsigned long, start, dma->vaddr),
> + PAGE_SIZE);
> + end_n = ALIGN(min_t(unsigned long, end, dma->vaddr + dma->size),
> + PAGE_SIZE);
> +
> + vfio_unmap_partial_iopf(iommu, dma,
> + start_n - dma->vaddr + dma->iova,
> + end_n - dma->vaddr + dma->iova);
> + }
> +
> + mutex_unlock(&iommu->lock);
> +}
> +
> +static const struct mmu_notifier_ops vfio_iommu_type1_mn_ops = {
> + .invalidate_range = mn_invalidate_range,
> +};
> +
> static long vfio_iommu_type1_ioctl(void *iommu_data,
> unsigned int cmd, unsigned long arg)
> {
Again, this patch series is difficult to follow because we're
introducing dead code until the mmu notifier actually has a path to be
registered. We shouldn't be taking any faults until iopf is enabled,
so it seems like we can add more of the core support alongside this
code.
Powered by blists - more mailing lists