On Fri, Oct 28, 2022 at 5:11 AM Alex Williamson
<[email protected]> wrote:
>
> On Thu, 27 Oct 2022 15:40:31 +0800
> Cindy Lu <[email protected]> wrote:
>
> > Move the function vfio_get_xlat_addr to softmmu/memory.c, and
> > change the name to memory_get_xlat_addr().So we can use this
> > function in other devices,such as vDPA device.
> >
> > Signed-off-by: Cindy Lu <[email protected]>
> > ---
> > hw/vfio/common.c | 92 ++-----------------------------------------
> > include/exec/memory.h | 4 ++
> > softmmu/memory.c | 84 +++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 92 insertions(+), 88 deletions(-)
> >
> > diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> > index ace9562a9b..2b5a9f3d8d 100644
> > --- a/hw/vfio/common.c
> > +++ b/hw/vfio/common.c
> > @@ -574,92 +574,6 @@ static bool
> > vfio_listener_skipped_section(MemoryRegionSection *section)
> > section->offset_within_address_space & (1ULL << 63);
> > }
> >
> > -/* Called with rcu_read_lock held. */
> > -static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> > - ram_addr_t *ram_addr, bool *read_only)
> > -{
> > - MemoryRegion *mr;
> > - hwaddr xlat;
> > - hwaddr len = iotlb->addr_mask + 1;
> > - bool writable = iotlb->perm & IOMMU_WO;
> > -
> > - /*
> > - * The IOMMU TLB entry we have just covers translation through
> > - * this IOMMU to its immediate target. We need to translate
> > - * it the rest of the way through to memory.
> > - */
> > - mr = address_space_translate(&address_space_memory,
> > - iotlb->translated_addr,
> > - &xlat, &len, writable,
> > - MEMTXATTRS_UNSPECIFIED);
> > - if (!memory_region_is_ram(mr)) {
> > - error_report("iommu map to non memory area %"HWADDR_PRIx"",
> > - xlat);
> > - return false;
> > - } else if (memory_region_has_ram_discard_manager(mr)) {
> > - RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
> > - MemoryRegionSection tmp = {
> > - .mr = mr,
> > - .offset_within_region = xlat,
> > - .size = int128_make64(len),
> > - };
> > -
> > - /*
> > - * Malicious VMs can map memory into the IOMMU, which is expected
> > - * to remain discarded. vfio will pin all pages, populating memory.
> > - * Disallow that. vmstate priorities make sure any
> > RamDiscardManager
> > - * were already restored before IOMMUs are restored.
> > - */
> > - if (!ram_discard_manager_is_populated(rdm, &tmp)) {
> > - error_report("iommu map to discarded memory (e.g., unplugged
> > via"
> > - " virtio-mem): %"HWADDR_PRIx"",
> > - iotlb->translated_addr);
> > - return false;
> > - }
> > -
> > - /*
> > - * Malicious VMs might trigger discarding of IOMMU-mapped memory.
> > The
> > - * pages will remain pinned inside vfio until unmapped, resulting
> > in a
> > - * higher memory consumption than expected. If memory would get
> > - * populated again later, there would be an inconsistency between
> > pages
> > - * pinned by vfio and pages seen by QEMU. This is the case until
> > - * unmapped from the IOMMU (e.g., during device reset).
> > - *
> > - * With malicious guests, we really only care about pinning more
> > memory
> > - * than expected. RLIMIT_MEMLOCK set for the user/process can
> > never be
> > - * exceeded and can be used to mitigate this problem.
> > - */
> > - warn_report_once("Using vfio with vIOMMUs and coordinated
> > discarding of"
> > - " RAM (e.g., virtio-mem) works, however,
> > malicious"
> > - " guests can trigger pinning of more memory than"
> > - " intended via an IOMMU. It's possible to
> > mitigate "
> > - " by setting/adjusting RLIMIT_MEMLOCK.");
> > - }
> > -
> > - /*
> > - * Translation truncates length to the IOMMU page size,
> > - * check that it did not truncate too much.
> > - */
> > - if (len & iotlb->addr_mask) {
> > - error_report("iommu has granularity incompatible with target AS");
> > - return false;
> > - }
> > -
> > - if (vaddr) {
> > - *vaddr = memory_region_get_ram_ptr(mr) + xlat;
> > - }
> > -
> > - if (ram_addr) {
> > - *ram_addr = memory_region_get_ram_addr(mr) + xlat;
> > - }
> > -
> > - if (read_only) {
> > - *read_only = !writable || mr->readonly;
> > - }
> > -
> > - return true;
> > -}
> > -
> > static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> > {
> > VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n);
> > @@ -682,7 +596,8 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n,
> > IOMMUTLBEntry *iotlb)
> > if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) {
> > bool read_only;
> >
> > - if (!vfio_get_xlat_addr(iotlb, &vaddr, NULL, &read_only)) {
> > + if (!memory_get_xlat_addr(iotlb, &vaddr, NULL, &read_only,
> > + &address_space_memory)) {
> > goto out;
> > }
> > /*
> > @@ -1359,7 +1274,8 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier
> > *n, IOMMUTLBEntry *iotlb)
> > }
> >
> > rcu_read_lock();
> > - if (vfio_get_xlat_addr(iotlb, NULL, &translated_addr, NULL)) {
> > + if (memory_get_xlat_addr(iotlb, NULL, &translated_addr, NULL,
> > + &address_space_memory)) {
> > int ret;
> >
> > ret = vfio_get_dirty_bitmap(container, iova, iotlb->addr_mask + 1,
> > diff --git a/include/exec/memory.h b/include/exec/memory.h
> > index bfb1de8eea..282de1d5ad 100644
> > --- a/include/exec/memory.h
> > +++ b/include/exec/memory.h
> > @@ -713,6 +713,10 @@ void
> > ram_discard_manager_register_listener(RamDiscardManager *rdm,
> > void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
> > RamDiscardListener *rdl);
> >
> > +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> > + ram_addr_t *ram_addr, bool *read_only,
> > + AddressSpace *as);
> > +
> > typedef struct CoalescedMemoryRange CoalescedMemoryRange;
> > typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd;
> >
> > diff --git a/softmmu/memory.c b/softmmu/memory.c
> > index 7ba2048836..8586863ffa 100644
> > --- a/softmmu/memory.c
> > +++ b/softmmu/memory.c
> > @@ -2121,6 +2121,90 @@ void
> > ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
> > rdmc->unregister_listener(rdm, rdl);
> > }
> >
> > +/* Called with rcu_read_lock held. */
> > +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> > + ram_addr_t *ram_addr, bool *read_only,
> > + AddressSpace *as)
> > +{
> > + MemoryRegion *mr;
> > + hwaddr xlat;
> > + hwaddr len = iotlb->addr_mask + 1;
> > + bool writable = iotlb->perm & IOMMU_WO;
> > +
> > + /*
> > + * The IOMMU TLB entry we have just covers translation through
> > + * this IOMMU to its immediate target. We need to translate
> > + * it the rest of the way through to memory.
> > + */
> > + mr = address_space_translate(as, iotlb->translated_addr, &xlat, &len,
> > + writable, MEMTXATTRS_UNSPECIFIED);
> > + if (!memory_region_is_ram(mr)) {
> > + error_report("iommu map to non memory area %" HWADDR_PRIx "",
> > xlat);
> > + return false;
> > + } else if (memory_region_has_ram_discard_manager(mr)) {
> > + RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
> > + MemoryRegionSection tmp = {
> > + .mr = mr,
> > + .offset_within_region = xlat,
> > + .size = int128_make64(len),
> > + };
> > +
> > + /*
> > + * Malicious VMs can map memory into the IOMMU, which is expected
> > + * to remain discarded. device will pin all pages, populating
> > memory.
> > + * Disallow that. vmstate priorities make sure any
> > RamDiscardManager
> > + * were already restored before IOMMUs are restored.
> > + */
> > + if (!ram_discard_manager_is_populated(rdm, &tmp)) {
> > + error_report("iommu map to discarded memory (e.g., unplugged
> > via"
> > + " virtio-mem): %" HWADDR_PRIx "",
> > + iotlb->translated_addr);
> > + return false;
> > + }
> > +
> > + /*
> > + * Malicious VMs might trigger discarding of IOMMU-mapped memory.
> > The
> > + * pages will remain pinned inside device until unmapped,
> > resulting in a
> > + * higher memory consumption than expected. If memory would get
> > + * populated again later, there would be an inconsistency between
> > pages
> > + * pinned by device and pages seen by QEMU. This is the case until
> > + * unmapped from the IOMMU (e.g., during device reset).
> > + *
> > + * With malicious guests, we really only care about pinning more
> > memory
> > + * than expected. RLIMIT_MEMLOCK set for the user/process can
> > never be
> > + * exceeded and can be used to mitigate this problem.
> > + */
> > + warn_report_once("Using device with vIOMMUs and coordinated
> > discarding"
> > + " of RAM (e.g., virtio-mem) works, however,
> > malicious"
> > + " guests can trigger pinning of more memory than"
> > + " intended via an IOMMU. It's possible to
> > mitigate "
> > + " by setting/adjusting RLIMIT_MEMLOCK.");
>
> Is this really fit to be in shared code? Simply replacing "vfio" with
> "device" for comments and warnings that are really of concern for a
> specific use case doesn't look much better to me.
>
> I think translating an unpopulated address, as in the previous test
> above, is generally invalid, but the comment is certainly trying to
> frame the severity of this error relative to a specific use case.
>
> Here we're generating an unconditional warning, assuming that this code
> path has been triggered by device code, for the condition of simply
> asking for a translation to a MemoryRegion under discard manager
> control? Again, isn't that an action that has implications for a
> specific use case of a device that supports pinning host memory?
Or can we rename the function to memory_get_xlat_addr_no_discard()?
This looks more general and fit for the caller that doesn't want to
map region that has a discard manager.
>
> Should the shared code be generating this warning, or could an optional
> pointer arg be updated to indicate a translation to discard manager
> controlled memory and this comment and warning should remain in the
> caller? Thanks,
I think this should also work.
Thanks
>
> Alex
>
> > + }
> > +
> > + /*
> > + * Translation truncates length to the IOMMU page size,
> > + * check that it did not truncate too much.
> > + */
> > + if (len & iotlb->addr_mask) {
> > + error_report("iommu has granularity incompatible with target AS");
> > + return false;
> > + }
> > +
> > + if (vaddr) {
> > + *vaddr = memory_region_get_ram_ptr(mr) + xlat;
> > + }
> > +
> > + if (ram_addr) {
> > + *ram_addr = memory_region_get_ram_addr(mr) + xlat;
> > + }
> > +
> > + if (read_only) {
> > + *read_only = !writable || mr->readonly;
> > + }
> > +
> > + return true;
> > +}
> > +
> > void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
> > {
> > uint8_t mask = 1 << client;
>
