Xuan Zhuo
2023-Apr-10 03:29 UTC
[PATCH vhost v6 08/11] virtio_ring: introduce virtqueue_dma_dev()
On Fri, 7 Apr 2023 07:02:34 -0400, "Michael S. Tsirkin" <mst at redhat.com> wrote:> On Thu, Apr 06, 2023 at 10:20:09AM -0700, Guenter Roeck wrote: > > Hi, > > > > On Mon, Mar 27, 2023 at 12:05:33PM +0800, Xuan Zhuo wrote: > > > Added virtqueue_dma_dev() to get DMA device for virtio. Then the > > > caller can do dma operation in advance. The purpose is to keep memory > > > mapped across multiple add/get buf operations. > > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > > > Acked-by: Jason Wang <jasowang at redhat.com> > > > > On sparc64, this patch results in > > > > [ 4.364643] Unable to handle kernel NULL pointer dereference > > [ 4.365157] tsk->{mm,active_mm}->context = 0000000000000000 > > [ 4.365394] tsk->{mm,active_mm}->pgd = fffff80000402000 > > [ 4.365611] \|/ ____ \|/ > > [ 4.365611] "@'/ .. \`@" > > [ 4.365611] /_| \__/ |_\ > > [ 4.365611] \__U_/ > > [ 4.366165] swapper/0(1): Oops [#1] > > [ 4.366630] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G N 6.3.0-rc5-next-20230405 #1 > > [ 4.367121] TSTATE: 0000004411001606 TPC: 00000000004375c0 TNPC: 00000000004375c4 Y: 00000002 Tainted: G N > > [ 4.367548] TPC: <dma_4u_supported+0x20/0x40> > > [ 4.368111] g0: 0000000000000000 g1: 0000000001a93a50 g2: 0000000000000000 g3: 0000000001a96170 > > [ 4.368439] g4: fffff8000416e9a0 g5: fffff8001dc98000 g6: fffff80004170000 g7: 0000000000000005 > > [ 4.368769] o0: 0000000000000000 o1: ffffffffffffffff o2: 0000000000000001 o3: fffff800040b78d8 > > [ 4.369095] o4: 0000000000000000 o5: 0000000000000000 sp: fffff80004172d51 ret_pc: 00000000004375ac > > [ 4.369934] RPC: <dma_4u_supported+0xc/0x40> > > [ 4.370160] l0: 0000000000000002 l1: 0000000000000002 l2: 0000000000000000 l3: 00000000ffffffff > > [ 4.370493] l4: 0000000000000001 l5: 000000000119d2b0 l6: fffff8000416e9a0 l7: 00000000018df000 > > [ 4.370820] i0: 0000000000000001 i1: ffffffffffffffff i2: fffff80004657758 i3: 000000000125ac00 > > [ 4.371145] i4: 0000000002362400 i5: 0000000000000000 i6: fffff80004172e01 i7: 000000000050e288 > > [ 4.371473] I7: <dma_set_mask+0x28/0x80> > > [ 4.371683] Call Trace: > > [ 4.371864] [<000000000050e288>] dma_set_mask+0x28/0x80 > > [ 4.372123] [<0000000000a83234>] virtio_dev_probe+0x14/0x400 > > [ 4.372348] [<0000000000ac7a18>] really_probe+0xb8/0x340 > > [ 4.372555] [<0000000000ac7d64>] driver_probe_device+0x24/0x120 > > [ 4.372794] [<0000000000ac8010>] __driver_attach+0x90/0x1a0 > > [ 4.373012] [<0000000000ac5b4c>] bus_for_each_dev+0x4c/0xa0 > > [ 4.373226] [<0000000000ac6d80>] bus_add_driver+0x140/0x1e0 > > [ 4.373440] [<0000000000ac8d94>] driver_register+0x74/0x120 > > [ 4.373653] [<0000000001b2a690>] virtio_net_driver_init+0x74/0xa8 > > [ 4.373886] [<0000000000427ee0>] do_one_initcall+0x60/0x340 > > [ 4.374099] [<0000000001b02f50>] kernel_init_freeable+0x1bc/0x228 > > [ 4.374330] [<0000000000f37264>] kernel_init+0x18/0x134 > > [ 4.374534] [<00000000004060e8>] ret_from_fork+0x1c/0x2c > > [ 4.374738] [<0000000000000000>] 0x0 > > [ 4.374981] Disabling lock debugging due to kernel taint > > [ 4.375237] Caller[000000000050e288]: dma_set_mask+0x28/0x80 > > [ 4.375477] Caller[0000000000a83234]: virtio_dev_probe+0x14/0x400 > > [ 4.375704] Caller[0000000000ac7a18]: really_probe+0xb8/0x340 > > [ 4.375916] Caller[0000000000ac7d64]: driver_probe_device+0x24/0x120 > > [ 4.376146] Caller[0000000000ac8010]: __driver_attach+0x90/0x1a0 > > [ 4.376365] Caller[0000000000ac5b4c]: bus_for_each_dev+0x4c/0xa0 > > [ 4.376583] Caller[0000000000ac6d80]: bus_add_driver+0x140/0x1e0 > > [ 4.376805] Caller[0000000000ac8d94]: driver_register+0x74/0x120 > > [ 4.377025] Caller[0000000001b2a690]: virtio_net_driver_init+0x74/0xa8 > > [ 4.377262] Caller[0000000000427ee0]: do_one_initcall+0x60/0x340 > > [ 4.377480] Caller[0000000001b02f50]: kernel_init_freeable+0x1bc/0x228 > > [ 4.377721] Caller[0000000000f37264]: kernel_init+0x18/0x134 > > [ 4.377930] Caller[00000000004060e8]: ret_from_fork+0x1c/0x2c > > [ 4.378140] Caller[0000000000000000]: 0x0 > > [ 4.378309] Instruction DUMP: > > [ 4.378339] 80a22000 > > [ 4.378556] 12400006 > > [ 4.378654] b0102001 > > [ 4.378746] <c2076658> > > [ 4.378838] b0102000 > > [ 4.378930] 80a04019 > > [ 4.379022] b1653001 > > [ 4.379115] 81cfe008 > > [ 4.379507] 913a2000 > > [ 4.379617] > > [ 4.380504] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 > > > > Reverting it fixes the problem. Bisect log attached. > > > > The reason is that dma_supported() calls dma_4u_supported(), which > > expects that dev->archdata.iommu has been initialized. However, > > this is not the case for the virtio device. Result is a null pointer > > dereference in dma_4u_supported(). > > > > static int dma_4u_supported(struct device *dev, u64 device_mask) > > { > > struct iommu *iommu = dev->archdata.iommu; > > > > if (ali_sound_dma_hack(dev, device_mask)) > > return 1; > > > > if (device_mask < iommu->dma_addr_mask) > > ^^^^^^^^^^^^^^^^^^^^ Crash location > > return 0; > > return 1; > > } > > > > Guenter > > This is from the unconditional call to dma_set_mask_and_coherent, right?Maybe not. The problem is that the dma_4u_supported() will be called in dma_supported(). The premise of this function is that IOMMU has been initialized. We hope to turn virtio dev into a direct dma device by dev->ops is null. The first step in DMA frame is obtaining ops. In many cases, get_arch_dma_ops() returns null. When ops is null, dma frame will use direct dma. static inline const struct dma_map_ops *get_dma_ops(struct device *dev) { if (dev->dma_ops) return dev->dma_ops; return get_arch_dma_ops(); } But rethink, this is unreliable. Some platforms have returned their own ops, including X86. Because the priority of dev->dma_ops is higher than get_arch_dma_ops(), we should not let dev->dma_ops be null. We should define a set of dma_ops to actively implement direct dMA.> > Xuan Zhuo, I feel there should an explanation in the commit log > about making this unconditional call. Why are you making it > in probe? > > I note that different virtio transports handle this differently. > And looking at this more I feel this should maybe be reverted for now: > > Your patch does: > > @@ -243,6 +244,11 @@ static int virtio_dev_probe(struct device *_d) > u64 driver_features; > u64 driver_features_legacy; > > + _d->dma_mask = &_d->coherent_dma_mask; > + err = dma_set_mask_and_coherent(_d, DMA_BIT_MASK(64)); > + if (err) > + return err; > + > /* We have a driver! */ > > > but for example virtio PCI has a 32 bit fallback. > > For example Virtio legacy also can't access 64 bit addresses at all, > so it does: > > rc = dma_set_mask(&pci_dev->dev, DMA_BIT_MASK(64));dma_set_mask() will also call dma_supported().> if (rc) { > rc = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(32)); > } else { > /* > * The virtio ring base address is expressed as a 32-bit PFN, > * with a page size of 1 << VIRTIO_PCI_QUEUE_ADDR_SHIFT. > */ > dma_set_coherent_mask(&pci_dev->dev, > DMA_BIT_MASK(32 + VIRTIO_PCI_QUEUE_ADDR_SHIFT)); > } > > > mmio tries a fallback to 32 bit if 64 bit fails which does not make > sense to me, but maybe I am wrong. > >These physical devices have IOMMU, so it is normal, but Virtio Dev does not have any physical IOMMU, so there are problems. I borrow from VDPA. So I think there are similar problems with VDPA. Thanks.> > > > > > --- > > # bad: [8417c8f5007bf4567ccffda850a3157c7d905f67] Add linux-next specific files for 20230405 > > # good: [7e364e56293bb98cae1b55fd835f5991c4e96e7d] Linux 6.3-rc5 > > git bisect start 'HEAD' 'v6.3-rc5' > > # good: [699c146eb5a03458f29e94cfde4d7dd7a36deeb4] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git > > git bisect good 699c146eb5a03458f29e94cfde4d7dd7a36deeb4 > > # good: [efe74e6476a9f04263288009910f07a26597386f] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux-dt.git > > git bisect good efe74e6476a9f04263288009910f07a26597386f > > # good: [24be607eedb226c1627973190a0b65cab39440b9] Merge branch 'char-misc-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git > > git bisect good 24be607eedb226c1627973190a0b65cab39440b9 > > # good: [5213285e3f212cf266c085c1c11041adda2bc63f] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git > > git bisect good 5213285e3f212cf266c085c1c11041adda2bc63f > > # bad: [e8f5d7e1787104da5977773ba5b3e1d502fdb9e3] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm.git > > git bisect bad e8f5d7e1787104da5977773ba5b3e1d502fdb9e3 > > # bad: [c08b5ad3300122790cef1bf7c1f51c554c778e4d] Merge branch 'gpio/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git > > git bisect bad c08b5ad3300122790cef1bf7c1f51c554c778e4d > > # good: [4ea0c97776bf8c63805eb0f8182d9c20072219d9] gpiolib: Check array_info for NULL only once in gpiod_get_array() > > git bisect good 4ea0c97776bf8c63805eb0f8182d9c20072219d9 > > # good: [b8e4bb0f05bef8334e689618c75cfed122f3a292] vdpa_sim: use kthread worker > > git bisect good b8e4bb0f05bef8334e689618c75cfed122f3a292 > > # bad: [ac1fa106f52a3ea2d2718a0de7d532d3d6c03e4e] Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git > > git bisect bad ac1fa106f52a3ea2d2718a0de7d532d3d6c03e4e > > # good: [56c8cf37fb0800ad66c926eb3d044e50691afa6e] virtio_ring: packed: separate dma codes > > git bisect good 56c8cf37fb0800ad66c926eb3d044e50691afa6e > > # good: [f19986b93ab7aa23f76dedf9fd8657f865324f78] virtio_ring: update document for virtqueue_add_* > > git bisect good f19986b93ab7aa23f76dedf9fd8657f865324f78 > > # bad: [60602b367dc928e2b3d6c1f21df5d05f90e37fa3] virtio_ring: correct the expression of the description of virtqueue_resize() > > git bisect bad 60602b367dc928e2b3d6c1f21df5d05f90e37fa3 > > # bad: [3a06353479111e1c9e072825bb0d0730e3a0f4e7] virtio_ring: introduce virtqueue_dma_dev() > > git bisect bad 3a06353479111e1c9e072825bb0d0730e3a0f4e7 > > # first bad commit: [3a06353479111e1c9e072825bb0d0730e3a0f4e7] virtio_ring: introduce virtqueue_dma_dev() >
Jason Wang
2023-Apr-10 05:14 UTC
[PATCH vhost v6 08/11] virtio_ring: introduce virtqueue_dma_dev()
On Mon, Apr 10, 2023 at 11:48?AM Xuan Zhuo <xuanzhuo at linux.alibaba.com> wrote:> > On Fri, 7 Apr 2023 07:02:34 -0400, "Michael S. Tsirkin" <mst at redhat.com> wrote: > > On Thu, Apr 06, 2023 at 10:20:09AM -0700, Guenter Roeck wrote: > > > Hi, > > > > > > On Mon, Mar 27, 2023 at 12:05:33PM +0800, Xuan Zhuo wrote: > > > > Added virtqueue_dma_dev() to get DMA device for virtio. Then the > > > > caller can do dma operation in advance. The purpose is to keep memory > > > > mapped across multiple add/get buf operations. > > > > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > > > > Acked-by: Jason Wang <jasowang at redhat.com> > > > > > > On sparc64, this patch results in > > > > > > [ 4.364643] Unable to handle kernel NULL pointer dereference > > > [ 4.365157] tsk->{mm,active_mm}->context = 0000000000000000 > > > [ 4.365394] tsk->{mm,active_mm}->pgd = fffff80000402000 > > > [ 4.365611] \|/ ____ \|/ > > > [ 4.365611] "@'/ .. \`@" > > > [ 4.365611] /_| \__/ |_\ > > > [ 4.365611] \__U_/ > > > [ 4.366165] swapper/0(1): Oops [#1] > > > [ 4.366630] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G N 6.3.0-rc5-next-20230405 #1 > > > [ 4.367121] TSTATE: 0000004411001606 TPC: 00000000004375c0 TNPC: 00000000004375c4 Y: 00000002 Tainted: G N > > > [ 4.367548] TPC: <dma_4u_supported+0x20/0x40> > > > [ 4.368111] g0: 0000000000000000 g1: 0000000001a93a50 g2: 0000000000000000 g3: 0000000001a96170 > > > [ 4.368439] g4: fffff8000416e9a0 g5: fffff8001dc98000 g6: fffff80004170000 g7: 0000000000000005 > > > [ 4.368769] o0: 0000000000000000 o1: ffffffffffffffff o2: 0000000000000001 o3: fffff800040b78d8 > > > [ 4.369095] o4: 0000000000000000 o5: 0000000000000000 sp: fffff80004172d51 ret_pc: 00000000004375ac > > > [ 4.369934] RPC: <dma_4u_supported+0xc/0x40> > > > [ 4.370160] l0: 0000000000000002 l1: 0000000000000002 l2: 0000000000000000 l3: 00000000ffffffff > > > [ 4.370493] l4: 0000000000000001 l5: 000000000119d2b0 l6: fffff8000416e9a0 l7: 00000000018df000 > > > [ 4.370820] i0: 0000000000000001 i1: ffffffffffffffff i2: fffff80004657758 i3: 000000000125ac00 > > > [ 4.371145] i4: 0000000002362400 i5: 0000000000000000 i6: fffff80004172e01 i7: 000000000050e288 > > > [ 4.371473] I7: <dma_set_mask+0x28/0x80> > > > [ 4.371683] Call Trace: > > > [ 4.371864] [<000000000050e288>] dma_set_mask+0x28/0x80 > > > [ 4.372123] [<0000000000a83234>] virtio_dev_probe+0x14/0x400 > > > [ 4.372348] [<0000000000ac7a18>] really_probe+0xb8/0x340 > > > [ 4.372555] [<0000000000ac7d64>] driver_probe_device+0x24/0x120 > > > [ 4.372794] [<0000000000ac8010>] __driver_attach+0x90/0x1a0 > > > [ 4.373012] [<0000000000ac5b4c>] bus_for_each_dev+0x4c/0xa0 > > > [ 4.373226] [<0000000000ac6d80>] bus_add_driver+0x140/0x1e0 > > > [ 4.373440] [<0000000000ac8d94>] driver_register+0x74/0x120 > > > [ 4.373653] [<0000000001b2a690>] virtio_net_driver_init+0x74/0xa8 > > > [ 4.373886] [<0000000000427ee0>] do_one_initcall+0x60/0x340 > > > [ 4.374099] [<0000000001b02f50>] kernel_init_freeable+0x1bc/0x228 > > > [ 4.374330] [<0000000000f37264>] kernel_init+0x18/0x134 > > > [ 4.374534] [<00000000004060e8>] ret_from_fork+0x1c/0x2c > > > [ 4.374738] [<0000000000000000>] 0x0 > > > [ 4.374981] Disabling lock debugging due to kernel taint > > > [ 4.375237] Caller[000000000050e288]: dma_set_mask+0x28/0x80 > > > [ 4.375477] Caller[0000000000a83234]: virtio_dev_probe+0x14/0x400 > > > [ 4.375704] Caller[0000000000ac7a18]: really_probe+0xb8/0x340 > > > [ 4.375916] Caller[0000000000ac7d64]: driver_probe_device+0x24/0x120 > > > [ 4.376146] Caller[0000000000ac8010]: __driver_attach+0x90/0x1a0 > > > [ 4.376365] Caller[0000000000ac5b4c]: bus_for_each_dev+0x4c/0xa0 > > > [ 4.376583] Caller[0000000000ac6d80]: bus_add_driver+0x140/0x1e0 > > > [ 4.376805] Caller[0000000000ac8d94]: driver_register+0x74/0x120 > > > [ 4.377025] Caller[0000000001b2a690]: virtio_net_driver_init+0x74/0xa8 > > > [ 4.377262] Caller[0000000000427ee0]: do_one_initcall+0x60/0x340 > > > [ 4.377480] Caller[0000000001b02f50]: kernel_init_freeable+0x1bc/0x228 > > > [ 4.377721] Caller[0000000000f37264]: kernel_init+0x18/0x134 > > > [ 4.377930] Caller[00000000004060e8]: ret_from_fork+0x1c/0x2c > > > [ 4.378140] Caller[0000000000000000]: 0x0 > > > [ 4.378309] Instruction DUMP: > > > [ 4.378339] 80a22000 > > > [ 4.378556] 12400006 > > > [ 4.378654] b0102001 > > > [ 4.378746] <c2076658> > > > [ 4.378838] b0102000 > > > [ 4.378930] 80a04019 > > > [ 4.379022] b1653001 > > > [ 4.379115] 81cfe008 > > > [ 4.379507] 913a2000 > > > [ 4.379617] > > > [ 4.380504] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 > > > > > > Reverting it fixes the problem. Bisect log attached. > > > > > > The reason is that dma_supported() calls dma_4u_supported(), which > > > expects that dev->archdata.iommu has been initialized. However, > > > this is not the case for the virtio device. Result is a null pointer > > > dereference in dma_4u_supported(). > > > > > > static int dma_4u_supported(struct device *dev, u64 device_mask) > > > { > > > struct iommu *iommu = dev->archdata.iommu; > > > > > > if (ali_sound_dma_hack(dev, device_mask)) > > > return 1; > > > > > > if (device_mask < iommu->dma_addr_mask) > > > ^^^^^^^^^^^^^^^^^^^^ Crash location > > > return 0; > > > return 1; > > > } > > > > > > Guenter > > > > This is from the unconditional call to dma_set_mask_and_coherent, right? > > Maybe not. > > The problem is that the dma_4u_supported() will be called in dma_supported(). > The premise of this function is that IOMMU has been initialized. > > We hope to turn virtio dev into a direct dma device by dev->ops is null. > > The first step in DMA frame is obtaining ops. In many cases, get_arch_dma_ops() > returns null. When ops is null, dma frame will use direct dma. > > static inline const struct dma_map_ops *get_dma_ops(struct device *dev) > { > if (dev->dma_ops) > return dev->dma_ops; > return get_arch_dma_ops(); > } > > But rethink, this is unreliable. Some platforms have returned their own ops, > including X86. > > Because the priority of dev->dma_ops is higher than get_arch_dma_ops(), we > should not let dev->dma_ops be null. We should define a set of dma_ops to > actively implement direct dMA.Then this will duplicate with existing DMA API helpers. Could we tweak the sparc or introduce a new flag for the device structure then the DMA API knows it needs to use direct mapping? Adding Christoph for more comments.> > > > > > Xuan Zhuo, I feel there should an explanation in the commit log > > about making this unconditional call. Why are you making it > > in probe? > > > > I note that different virtio transports handle this differently. > > And looking at this more I feel this should maybe be reverted for now: > > > > Your patch does: > > > > @@ -243,6 +244,11 @@ static int virtio_dev_probe(struct device *_d) > > u64 driver_features; > > u64 driver_features_legacy; > > > > + _d->dma_mask = &_d->coherent_dma_mask; > > + err = dma_set_mask_and_coherent(_d, DMA_BIT_MASK(64)); > > + if (err) > > + return err; > > + > > /* We have a driver! */ > > > > > > but for example virtio PCI has a 32 bit fallback. > > > > For example Virtio legacy also can't access 64 bit addresses at all, > > so it does: > > > > rc = dma_set_mask(&pci_dev->dev, DMA_BIT_MASK(64)); > > dma_set_mask() will also call dma_supported(). > > > > if (rc) { > > rc = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(32)); > > } else { > > /* > > * The virtio ring base address is expressed as a 32-bit PFN, > > * with a page size of 1 << VIRTIO_PCI_QUEUE_ADDR_SHIFT. > > */ > > dma_set_coherent_mask(&pci_dev->dev, > > DMA_BIT_MASK(32 + VIRTIO_PCI_QUEUE_ADDR_SHIFT)); > > } > > > > > > mmio tries a fallback to 32 bit if 64 bit fails which does not make > > sense to me, but maybe I am wrong. > > > > > > These physical devices have IOMMU, so it is normal, but Virtio Dev does not have > any physical IOMMU, so there are problems. I borrow from VDPA. So I think > there are similar problems with VDPA.Yes. Thanks> > > Thanks. > > > > > > > > > > > > > --- > > > # bad: [8417c8f5007bf4567ccffda850a3157c7d905f67] Add linux-next specific files for 20230405 > > > # good: [7e364e56293bb98cae1b55fd835f5991c4e96e7d] Linux 6.3-rc5 > > > git bisect start 'HEAD' 'v6.3-rc5' > > > # good: [699c146eb5a03458f29e94cfde4d7dd7a36deeb4] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git > > > git bisect good 699c146eb5a03458f29e94cfde4d7dd7a36deeb4 > > > # good: [efe74e6476a9f04263288009910f07a26597386f] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux-dt.git > > > git bisect good efe74e6476a9f04263288009910f07a26597386f > > > # good: [24be607eedb226c1627973190a0b65cab39440b9] Merge branch 'char-misc-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git > > > git bisect good 24be607eedb226c1627973190a0b65cab39440b9 > > > # good: [5213285e3f212cf266c085c1c11041adda2bc63f] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git > > > git bisect good 5213285e3f212cf266c085c1c11041adda2bc63f > > > # bad: [e8f5d7e1787104da5977773ba5b3e1d502fdb9e3] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm.git > > > git bisect bad e8f5d7e1787104da5977773ba5b3e1d502fdb9e3 > > > # bad: [c08b5ad3300122790cef1bf7c1f51c554c778e4d] Merge branch 'gpio/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git > > > git bisect bad c08b5ad3300122790cef1bf7c1f51c554c778e4d > > > # good: [4ea0c97776bf8c63805eb0f8182d9c20072219d9] gpiolib: Check array_info for NULL only once in gpiod_get_array() > > > git bisect good 4ea0c97776bf8c63805eb0f8182d9c20072219d9 > > > # good: [b8e4bb0f05bef8334e689618c75cfed122f3a292] vdpa_sim: use kthread worker > > > git bisect good b8e4bb0f05bef8334e689618c75cfed122f3a292 > > > # bad: [ac1fa106f52a3ea2d2718a0de7d532d3d6c03e4e] Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git > > > git bisect bad ac1fa106f52a3ea2d2718a0de7d532d3d6c03e4e > > > # good: [56c8cf37fb0800ad66c926eb3d044e50691afa6e] virtio_ring: packed: separate dma codes > > > git bisect good 56c8cf37fb0800ad66c926eb3d044e50691afa6e > > > # good: [f19986b93ab7aa23f76dedf9fd8657f865324f78] virtio_ring: update document for virtqueue_add_* > > > git bisect good f19986b93ab7aa23f76dedf9fd8657f865324f78 > > > # bad: [60602b367dc928e2b3d6c1f21df5d05f90e37fa3] virtio_ring: correct the expression of the description of virtqueue_resize() > > > git bisect bad 60602b367dc928e2b3d6c1f21df5d05f90e37fa3 > > > # bad: [3a06353479111e1c9e072825bb0d0730e3a0f4e7] virtio_ring: introduce virtqueue_dma_dev() > > > git bisect bad 3a06353479111e1c9e072825bb0d0730e3a0f4e7 > > > # first bad commit: [3a06353479111e1c9e072825bb0d0730e3a0f4e7] virtio_ring: introduce virtqueue_dma_dev() > > >