On 211217 1458, Philippe Mathieu-Daudé wrote: > On 12/17/21 04:08, Alexander Bulekov wrote: > > Here's my shot at fixing dma-reentracy issues. This patch adds a flag to > > the DeviceState, which is set/checked when we call an accessor > > associated with the device's IO MRs. > > Your approach is exactly what Gerd suggested: > https://www.mail-archive.com/qemu-devel@nongnu.org/msg831437.html
Yes - my bad for not searching my mail more carefully. > > > The problem, in short, as I understand it: For the vast majority of > > cases, we want to prevent a device from accessing it's own PIO/MMIO > > regions over DMA. > > > > This patch/solution is based on some assumptions: > > 1. DMA accesses that hit mmio regions are only dangerous if they end up > > interacting with memory-regions belonging to the device initiating the > > DMA. > > Not dangerous: sdhci_pio->dma_write->e1000_mmio > > Dangerous: sdhci_pio->dma_write->sdhci_mmio > > It doesn't have to be dangerous, see Paolo's example which > invalidated my previous attempt and forced me to write 24 > patches in multiples series to keep the "niche" cases working: > https://www.mail-archive.com/qemu-block@nongnu.org/msg72939.html I don't understand what IO accesses this decodes to. This is loading a picture into VRAM? -Alex > > > > > 2. Most devices do not interact with their own PIO/MMIO memory-regions > > using DMA. > > > > 3. There is no way for there to be multiple simultaneous accesses to a > > device's PIO/MMIO memory-regions. > > > > 4. All devices are QOMified :-) > > > > With this patch, I wasn't able to reproduce the issues being tracked > > here, with QTest reproducers: > > https://gitlab.com/qemu-project/qemu/-/issues/556 > > > > This passes the i386 qos/qtests for me and I was able to boot some > > linux/windows > > VMs with basic devices configured, without any apparent problems. > > > > Cc: Philippe Mathieu-Daudé <phi...@redhat.com> > > Cc: Mauro Matteo Cascella <mcasc...@redhat.com> > > Cc: Qiuhao Li <qiuhao...@outlook.com> > > Cc: Peter Xu <pet...@redhat.com> > > Cc: Jason Wang <jasow...@redhat.com> > > Cc: David Hildenbrand <da...@redhat.com> > > Cc: Gerd Hoffmann <kra...@redhat.com> > > Cc: Peter Maydell <peter.mayd...@linaro.org> > > Cc: Li Qiang <liq...@gmail.com> > > Cc: Thomas Huth <th...@redhat.com> > > Cc: Laurent Vivier <lviv...@redhat.com> > > Cc: Bandan Das <b...@redhat.com> > > Cc: Edgar E. Iglesias <edgar.igles...@gmail.com> > > Cc: Darren Kenny <darren.ke...@oracle.com> > > Cc: Bin Meng <bin.m...@windriver.com> > > Cc: Paolo Bonzini <pbonz...@redhat.com> > > Cc: Stefan Hajnoczi <stefa...@redhat.com> > > > > Signed-off-by: Alexander Bulekov <alx...@bu.edu> > > --- > > include/hw/qdev-core.h | 1 + > > softmmu/memory.c | 15 +++++++++++++++ > > softmmu/trace-events | 1 + > > 3 files changed, 17 insertions(+) > > > > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > > index 20d3066595..32f7c779ab 100644 > > --- a/include/hw/qdev-core.h > > +++ b/include/hw/qdev-core.h > > @@ -193,6 +193,7 @@ struct DeviceState { > > int instance_id_alias; > > int alias_required_for_version; > > ResettableState reset; > > + int engaged_in_direct_io; > > }; > > > > struct DeviceListener { > > diff --git a/softmmu/memory.c b/softmmu/memory.c > > index 7340e19ff5..255c3c602f 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) { > > + dev = (DeviceState *) object_dynamic_cast(mr->owner, TYPE_DEVICE); > > + if (dev->engaged_in_direct_io) { > > + trace_memory_region_reentrant_io(get_cpu_index(), mr, addr, > > size); > > + return MEMTX_ERROR; > > + } > > + dev->engaged_in_direct_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->engaged_in_direct_io = false; > > + } > > return r; > > } > > > > diff --git a/softmmu/trace-events b/softmmu/trace-events > > index 9c88887b3c..d7228316db 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)" > > >
