Re: [PATCH v6 0/4] memory: prevent dma-reentracy issues

[Thomas Huth]

On 13/02/2023 03.11, Alexander Bulekov wrote:
> ping

I think it would be really good to finally get these dma-reentrancy issues 
fixed! Who's supposed to pick up these patches? Paolo? David? Peter?

 Thomas


> On 230204 2307, Alexander Bulekov wrote:
> > These patches aim to solve two types of DMA-reentrancy issues:
> >    
> > 1.) mmio -> dma -> mmio case
> > To solve this, we track whether the device is engaged in io by
> > checking/setting a reentrancy-guard within APIs used for MMIO access.
> >    
> > 2.) bh -> dma write -> mmio case
> > This case is trickier, since we dont have a generic way to associate a
> > bh with the underlying Device/DeviceState. Thus, this version allows a
> > device to associate a reentrancy-guard with a bh, when creating it.
> > (Instead of calling qemu_bh_new, you call qemu_bh_new_guarded)
> >    
> > I replaced most of the qemu_bh_new invocations with the guarded analog,
> > except for the ones where the DeviceState was not trivially accessible.
> >
> > v5 -> v6:
> >      - Only apply checkpatch checks to code in paths containing "/hw/"
> >        (/hw/ and include/hw/)
> >      - Fix a bug in a _guarded call added to hw/block/virtio-blk.c
> > v4-> v5:
> >      - Add corresponding checkpatch checks
> >      - Save/restore reentrancy-flag when entering/exiting BHs
> >      - Improve documentation
> >      - Check object_dynamic_cast return value
> >    
> > v3 -> v4: Instead of changing all of the DMA APIs, instead add an
> >      optional reentrancy guard to the BH API.
> >
> > v2 -> v3: Bite the bullet and modify the DMA APIs, rather than
> >      attempting to guess DeviceStates in BHs.
> >
> > Alexander Bulekov (4):
> >    memory: prevent dma-reentracy issues
> >    async: Add an optional reentrancy guard to the BH API
> >    checkpatch: add qemu_bh_new/aio_bh_new checks
> >    hw: replace most qemu_bh_new calls with qemu_bh_new_guarded
> >
> >   docs/devel/multiple-iothreads.txt |  7 +++++++
> >   hw/9pfs/xen-9p-backend.c          |  4 +++-
> >   hw/block/dataplane/virtio-blk.c   |  3 ++-
> >   hw/block/dataplane/xen-block.c    |  5 +++--
> >   hw/char/virtio-serial-bus.c       |  3 ++-
> >   hw/display/qxl.c                  |  9 ++++++---
> >   hw/display/virtio-gpu.c           |  6 ++++--
> >   hw/ide/ahci.c                     |  3 ++-
> >   hw/ide/core.c                     |  3 ++-
> >   hw/misc/imx_rngc.c                |  6 ++++--
> >   hw/misc/macio/mac_dbdma.c         |  2 +-
> >   hw/net/virtio-net.c               |  3 ++-
> >   hw/nvme/ctrl.c                    |  6 ++++--
> >   hw/scsi/mptsas.c                  |  3 ++-
> >   hw/scsi/scsi-bus.c                |  3 ++-
> >   hw/scsi/vmw_pvscsi.c              |  3 ++-
> >   hw/usb/dev-uas.c                  |  3 ++-
> >   hw/usb/hcd-dwc2.c                 |  3 ++-
> >   hw/usb/hcd-ehci.c                 |  3 ++-
> >   hw/usb/hcd-uhci.c                 |  2 +-
> >   hw/usb/host-libusb.c              |  6 ++++--
> >   hw/usb/redirect.c                 |  6 ++++--
> >   hw/usb/xen-usb.c                  |  3 ++-
> >   hw/virtio/virtio-balloon.c        |  5 +++--
> >   hw/virtio/virtio-crypto.c         |  3 ++-
> >   include/block/aio.h               | 18 ++++++++++++++++--
> >   include/hw/qdev-core.h            |  7 +++++++
> >   include/qemu/main-loop.h          |  7 +++++--
> >   scripts/checkpatch.pl             |  8 ++++++++
> >   softmmu/memory.c                  | 17 +++++++++++++++++
> >   softmmu/trace-events              |  1 +
> >   tests/unit/ptimer-test-stubs.c    |  3 ++-
> >   util/async.c                      | 18 +++++++++++++++++-
> >   util/main-loop.c                  |  5 +++--
> >   util/trace-events                 |  1 +
> >   35 files changed, 147 insertions(+), 41 deletions(-)
> >
> > --
> > 2.39.0