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Iglesias" , Darren Kenny , Bin Meng , Paolo Bonzini , "Michael S . Tsirkin" , Marcel Apfelbaum , =?UTF-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Eduardo Habkost , Jon Maloy , Siqi Chen Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2607:f8b0:4864:20::b29; envelope-from=stefanha@gmail.com; helo=mail-yb1-xb29.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, 28 Oct 2022 at 15:19, Alexander Bulekov wrote: > > Add transitionary DMA APIs which associate accesses with the device > initiating them. The modified APIs maintain a "MemReentrancyGuard" in > the DeviceState, which is used to prevent DMA re-entrancy issues. > The MemReentrancyGuard is set/checked when entering IO handlers and when > initiating a DMA access. > > 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 > > Signed-off-by: Alexander Bulekov > --- > include/hw/qdev-core.h | 2 ++ > include/sysemu/dma.h | 41 +++++++++++++++++++++++++++++++++++++++++ > softmmu/memory.c | 15 +++++++++++++++ > softmmu/trace-events | 1 + > 4 files changed, 59 insertions(+) > > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > index 785dd5a56e..ab78d211af 100644 > --- a/include/hw/qdev-core.h > +++ b/include/hw/qdev-core.h > @@ -8,6 +8,7 @@ > #include "qom/object.h" > #include "hw/hotplug.h" > #include "hw/resettable.h" > +#include "sysemu/dma.h" > > enum { > DEV_NVECTORS_UNSPECIFIED = -1, > @@ -194,6 +195,7 @@ struct DeviceState { > int alias_required_for_version; > ResettableState reset; > GSList *unplug_blockers; > + MemReentrancyGuard mem_reentrancy_guard; > }; > > struct DeviceListener { > diff --git a/include/sysemu/dma.h b/include/sysemu/dma.h > index a1ac5bc1b5..879b666bbb 100644 > --- a/include/sysemu/dma.h > +++ b/include/sysemu/dma.h > @@ -15,6 +15,10 @@ > #include "block/block.h" > #include "block/accounting.h" > > +typedef struct { > + bool engaged_in_io; > +} MemReentrancyGuard; Please add a doc comment that explains the purpose of MemReentrancyGuard. > + > typedef enum { > DMA_DIRECTION_TO_DEVICE = 0, > DMA_DIRECTION_FROM_DEVICE = 1, > @@ -321,4 +325,41 @@ void dma_acct_start(BlockBackend *blk, BlockAcctCookie *cookie, > uint64_t dma_aligned_pow2_mask(uint64_t start, uint64_t end, > int max_addr_bits); > > +#define REENTRANCY_GUARD(func, ret_type, dev, ...) \ > + ({\ > + ret_type retval;\ > + MemReentrancyGuard prior_guard_state = dev->mem_reentrancy_guard;\ > + dev->mem_reentrancy_guard.engaged_in_io = 1;\ Please use true/false for bool constants. That way it's obvious to the reader that this is a bool and not an int. > + retval = func(__VA_ARGS__);\ > + dev->mem_reentrancy_guard = prior_guard_state;\ > + retval;\ > + }) I'm trying to understand the purpose of this macro. It restores the previous state of mem_reentrancy_guard, implying that this is sometimes called when the guard is already true (i.e. from MemoryRegion callbacks). It can also be called in the BH case and I think that's why mem_reentrancy_guard is set to true here. Using BHs to avoid deep stacks and re-entrancy is a valid technique though, and this macro seems to be designed to prevent it. Can you explain a bit more about how this is supposed to be used? If this macro is a public API that other parts of QEMU will use, then the following approach is more consistent with how the lock guard macros work: REENTRANCY_GUARD(dev) { retval = func(1, 2, 3); } It's also more readable then: REENTRANCY_GUARD(func, int, dev, 1, 2, 3); ? > +#define REENTRANCY_GUARD_NORET(func, dev, ...) \ > + ({\ > + MemReentrancyGuard prior_guard_state = dev->mem_reentrancy_guard;\ > + dev->mem_reentrancy_guard.engaged_in_io = 1;\ > + func(__VA_ARGS__);\ > + dev->mem_reentrancy_guard = prior_guard_state;\ > + }) > +#define dma_memory_rw_guarded(dev, ...) \ > + REENTRANCY_GUARD(dma_memory_rw, MemTxResult, dev, __VA_ARGS__) > +#define dma_memory_read_guarded(dev, ...) \ > + REENTRANCY_GUARD(dma_memory_read, MemTxResult, dev, __VA_ARGS__) > +#define dma_memory_write_guarded(dev, ...) \ > + REENTRANCY_GUARD(dma_memory_write, MemTxResult, dev, __VA_ARGS__) > +#define dma_memory_set_guarded(dev, ...) \ > + REENTRANCY_GUARD(dma_memory_set, MemTxResult, dev, __VA_ARGS__) > +#define dma_memory_map_guarded(dev, ...) \ > + REENTRANCY_GUARD(dma_memory_map, void*, dev, __VA_ARGS__) > +#define dma_memory_unmap_guarded(dev, ...) \ > + REENTRANCY_GUARD_NORET(dma_memory_unmap, dev, __VA_ARGS__) > +#define ldub_dma_guarded(dev, ...) \ > + REENTRANCY_GUARD(ldub_dma, MemTxResult, dev, __VA_ARGS__) > +#define stb_dma_guarded(dev, ...) \ > + REENTRANCY_GUARD(stb_dma, MemTxResult, dev, __VA_ARGS__) > +#define dma_buf_read_guarded(dev, ...) \ > + REENTRANCY_GUARD(dma_buf_read, MemTxResult, dev, __VA_ARGS__) > +#define dma_buf_write_guarded(dev, ...) \ > + REENTRANCY_GUARD(dma_buf_read, MemTxResult, dev, __VA_ARGS__) > + > #endif > diff --git a/softmmu/memory.c b/softmmu/memory.c > index 7ba2048836..c44dc75149 100644 > --- a/softmmu/memory.c > +++ b/softmmu/memory.c > @@ -532,6 +532,7 @@ static MemTxResult access_with_adjusted_size(hwaddr addr, > uint64_t access_mask; > unsigned access_size; > unsigned i; > + DeviceState *dev = NULL; > MemTxResult r = MEMTX_OK; > > if (!access_size_min) { > @@ -541,6 +542,17 @@ static MemTxResult access_with_adjusted_size(hwaddr addr, > access_size_max = 4; > } > > + /* Do not allow more than one simultanous access to a device's IO Regions */ > + if (mr->owner && > + !mr->ram_device && !mr->ram && !mr->rom_device && !mr->readonly) { Why are readonly MemoryRegions exempt? > + dev = (DeviceState *) object_dynamic_cast(mr->owner, TYPE_DEVICE); > + if (dev->mem_reentrancy_guard.engaged_in_io) { > + trace_memory_region_reentrant_io(get_cpu_index(), mr, addr, size); > + return MEMTX_ERROR; > + } > + dev->mem_reentrancy_guard.engaged_in_io = true; > + } > + > /* FIXME: support unaligned access? */ > access_size = MAX(MIN(size, access_size_max), access_size_min); > access_mask = MAKE_64BIT_MASK(0, access_size * 8); > @@ -555,6 +567,9 @@ static MemTxResult access_with_adjusted_size(hwaddr addr, > access_mask, attrs); > } > } > + if (dev) { > + dev->mem_reentrancy_guard.engaged_in_io = false; > + } > return r; > } > > diff --git a/softmmu/trace-events b/softmmu/trace-events > index 22606dc27b..62d04ea9a7 100644 > --- a/softmmu/trace-events > +++ b/softmmu/trace-events > @@ -13,6 +13,7 @@ memory_region_ops_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, u > memory_region_ops_write(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size, const char *name) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u name '%s'" > memory_region_subpage_read(int cpu_index, void *mr, uint64_t offset, uint64_t value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size %u" > memory_region_subpage_write(int cpu_index, void *mr, uint64_t offset, uint64_t value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size %u" > +memory_region_reentrant_io(int cpu_index, void *mr, uint64_t offset, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" size %u" > memory_region_ram_device_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u" > memory_region_ram_device_write(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u" > memory_region_sync_dirty(const char *mr, const char *listener, int global) "mr '%s' listener '%s' synced (global=%d)" > -- > 2.27.0 > >