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Re: [PATCH v4 1/3] memory: prevent dma-reentracy issues
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From: |
Stefan Hajnoczi |
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Subject: |
Re: [PATCH v4 1/3] memory: prevent dma-reentracy issues |
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Date: |
Wed, 25 Jan 2023 16:12:29 -0500 |
On Thu, Jan 19, 2023 at 02:03:06AM -0500, Alexander Bulekov wrote:
> Add a flag to the DeviceState, when a device is engaged in PIO/MMIO/DMA.
> This flag is set/checked prior to calling a device's MemoryRegion
> handlers, and set when device code initiates DMA. The purpose of this
> flag is to prevent two types of DMA-based reentrancy issues:
>
> 1.) mmio -> dma -> mmio case
> 2.) bh -> dma write -> mmio case
>
> These issues have led to problems such as stack-exhaustion and
> use-after-frees.
>
> Summary of the problem from Peter Maydell:
> https://lore.kernel.org/qemu-devel/CAFEAcA_23vc7hE3iaM-JVA6W38LK4hJoWae5KcknhPRD5fPBZA@mail.gmail.com
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/62
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/540
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/541
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/556
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/557
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/827
> Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
> ---
> include/hw/qdev-core.h | 7 +++++++
> softmmu/memory.c | 15 +++++++++++++++
> softmmu/trace-events | 1 +
> 3 files changed, 23 insertions(+)
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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