* [PATCH 1/1] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout @ 2018-08-06 12:31 Zhen Lei 2018-08-08 10:12 ` Will Deacon 0 siblings, 1 reply; 5+ messages in thread From: Zhen Lei @ 2018-08-06 12:31 UTC (permalink / raw) To: linux-arm-kernel The condition "(int)(VAL - sync_idx) >= 0" to break loop in function __arm_smmu_sync_poll_msi requires that sync_idx must be increased monotonously according to the sequence of the CMDs in the cmdq. But ".msidata = atomic_inc_return_relaxed(&smmu->sync_nr)" is not protected by spinlock, so the following scenarios may appear: cpu0 cpu1 msidata=0 msidata=1 insert cmd1 insert cmd0 smmu execute cmd1 smmu execute cmd0 poll timeout, because msidata=1 is overridden by cmd0, that means VAL=0, sync_idx=1. Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- drivers/iommu/arm-smmu-v3.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 1d64710..4810f61 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -566,7 +566,7 @@ struct arm_smmu_device { int gerr_irq; int combined_irq; - atomic_t sync_nr; + u32 sync_nr; unsigned long ias; /* IPA */ unsigned long oas; /* PA */ @@ -836,7 +836,6 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV); cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH); cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB); - cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent->sync.msidata); cmd[1] |= ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK; break; default: @@ -947,7 +946,6 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) struct arm_smmu_cmdq_ent ent = { .opcode = CMDQ_OP_CMD_SYNC, .sync = { - .msidata = atomic_inc_return_relaxed(&smmu->sync_nr), .msiaddr = virt_to_phys(&smmu->sync_count), }, }; @@ -955,6 +953,8 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) arm_smmu_cmdq_build_cmd(cmd, &ent); spin_lock_irqsave(&smmu->cmdq.lock, flags); + ent.sync.msidata = ++smmu->sync_nr; + cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent.sync.msidata); arm_smmu_cmdq_insert_cmd(smmu, cmd); spin_unlock_irqrestore(&smmu->cmdq.lock, flags); @@ -2179,7 +2179,6 @@ static int arm_smmu_init_structures(struct arm_smmu_device *smmu) { int ret; - atomic_set(&smmu->sync_nr, 0); ret = arm_smmu_init_queues(smmu); if (ret) return ret; -- 1.8.3 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH 1/1] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout 2018-08-06 12:31 [PATCH 1/1] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout Zhen Lei @ 2018-08-08 10:12 ` Will Deacon 2018-08-09 1:30 ` Leizhen (ThunderTown) 0 siblings, 1 reply; 5+ messages in thread From: Will Deacon @ 2018-08-08 10:12 UTC (permalink / raw) To: linux-arm-kernel Hi Thunder, On Mon, Aug 06, 2018 at 08:31:29PM +0800, Zhen Lei wrote: > The condition "(int)(VAL - sync_idx) >= 0" to break loop in function > __arm_smmu_sync_poll_msi requires that sync_idx must be increased > monotonously according to the sequence of the CMDs in the cmdq. > > But ".msidata = atomic_inc_return_relaxed(&smmu->sync_nr)" is not protected > by spinlock, so the following scenarios may appear: > cpu0 cpu1 > msidata=0 > msidata=1 > insert cmd1 > insert cmd0 > smmu execute cmd1 > smmu execute cmd0 > poll timeout, because msidata=1 is overridden by > cmd0, that means VAL=0, sync_idx=1. Oh yuck, you're right! We probably want a CC stable on this. Did you see this go wrong in practice? One comment on your patch... > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > --- > drivers/iommu/arm-smmu-v3.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c > index 1d64710..4810f61 100644 > --- a/drivers/iommu/arm-smmu-v3.c > +++ b/drivers/iommu/arm-smmu-v3.c > @@ -566,7 +566,7 @@ struct arm_smmu_device { > > int gerr_irq; > int combined_irq; > - atomic_t sync_nr; > + u32 sync_nr; > > unsigned long ias; /* IPA */ > unsigned long oas; /* PA */ > @@ -836,7 +836,6 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) > cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV); > cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH); > cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB); > - cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent->sync.msidata); > cmd[1] |= ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK; > break; > default: > @@ -947,7 +946,6 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) > struct arm_smmu_cmdq_ent ent = { > .opcode = CMDQ_OP_CMD_SYNC, > .sync = { > - .msidata = atomic_inc_return_relaxed(&smmu->sync_nr), > .msiaddr = virt_to_phys(&smmu->sync_count), > }, > }; > @@ -955,6 +953,8 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) > arm_smmu_cmdq_build_cmd(cmd, &ent); > > spin_lock_irqsave(&smmu->cmdq.lock, flags); > + ent.sync.msidata = ++smmu->sync_nr; > + cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent.sync.msidata); I really don't like splitting this out from building the rest of the command. Can you just move the call to arm_smmu_cmdq_build_cmd into the critical section, please? Thanks, Will ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 1/1] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout 2018-08-08 10:12 ` Will Deacon @ 2018-08-09 1:30 ` Leizhen (ThunderTown) 2018-08-09 8:49 ` Will Deacon 0 siblings, 1 reply; 5+ messages in thread From: Leizhen (ThunderTown) @ 2018-08-09 1:30 UTC (permalink / raw) To: linux-arm-kernel On 2018/8/8 18:12, Will Deacon wrote: > Hi Thunder, > > On Mon, Aug 06, 2018 at 08:31:29PM +0800, Zhen Lei wrote: >> The condition "(int)(VAL - sync_idx) >= 0" to break loop in function >> __arm_smmu_sync_poll_msi requires that sync_idx must be increased >> monotonously according to the sequence of the CMDs in the cmdq. >> >> But ".msidata = atomic_inc_return_relaxed(&smmu->sync_nr)" is not protected >> by spinlock, so the following scenarios may appear: >> cpu0 cpu1 >> msidata=0 >> msidata=1 >> insert cmd1 >> insert cmd0 >> smmu execute cmd1 >> smmu execute cmd0 >> poll timeout, because msidata=1 is overridden by >> cmd0, that means VAL=0, sync_idx=1. > > Oh yuck, you're right! We probably want a CC stable on this. Did you see > this go wrong in practice? Just misreported and make the caller wait for a long time until TIMEOUT. It's rare to happen, because any other CMD_SYNC during the waiting period will break it. > > One comment on your patch... > >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >> --- >> drivers/iommu/arm-smmu-v3.c | 7 +++---- >> 1 file changed, 3 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c >> index 1d64710..4810f61 100644 >> --- a/drivers/iommu/arm-smmu-v3.c >> +++ b/drivers/iommu/arm-smmu-v3.c >> @@ -566,7 +566,7 @@ struct arm_smmu_device { >> >> int gerr_irq; >> int combined_irq; >> - atomic_t sync_nr; >> + u32 sync_nr; >> >> unsigned long ias; /* IPA */ >> unsigned long oas; /* PA */ >> @@ -836,7 +836,6 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) >> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV); >> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH); >> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB); >> - cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent->sync.msidata); >> cmd[1] |= ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK; >> break; >> default: >> @@ -947,7 +946,6 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) >> struct arm_smmu_cmdq_ent ent = { >> .opcode = CMDQ_OP_CMD_SYNC, >> .sync = { >> - .msidata = atomic_inc_return_relaxed(&smmu->sync_nr), >> .msiaddr = virt_to_phys(&smmu->sync_count), >> }, >> }; >> @@ -955,6 +953,8 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) >> arm_smmu_cmdq_build_cmd(cmd, &ent); >> >> spin_lock_irqsave(&smmu->cmdq.lock, flags); >> + ent.sync.msidata = ++smmu->sync_nr; >> + cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent.sync.msidata); > > I really don't like splitting this out from building the rest of the > command. Can you just move the call to arm_smmu_cmdq_build_cmd into the > critical section, please? OK. I have considered that before, just worry it will increase the compition of spinlock. In addition, I will append a optimization patch: the adjacent CMD_SYNCs, we only need one. > > Thanks, > > Will > > . > -- Thanks! BestRegards ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 1/1] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout 2018-08-09 1:30 ` Leizhen (ThunderTown) @ 2018-08-09 8:49 ` Will Deacon 2018-08-09 10:05 ` Leizhen (ThunderTown) 0 siblings, 1 reply; 5+ messages in thread From: Will Deacon @ 2018-08-09 8:49 UTC (permalink / raw) To: linux-arm-kernel On Thu, Aug 09, 2018 at 09:30:51AM +0800, Leizhen (ThunderTown) wrote: > On 2018/8/8 18:12, Will Deacon wrote: > > On Mon, Aug 06, 2018 at 08:31:29PM +0800, Zhen Lei wrote: > >> The condition "(int)(VAL - sync_idx) >= 0" to break loop in function > >> __arm_smmu_sync_poll_msi requires that sync_idx must be increased > >> monotonously according to the sequence of the CMDs in the cmdq. > >> > >> But ".msidata = atomic_inc_return_relaxed(&smmu->sync_nr)" is not protected > >> by spinlock, so the following scenarios may appear: > >> cpu0 cpu1 > >> msidata=0 > >> msidata=1 > >> insert cmd1 > >> insert cmd0 > >> smmu execute cmd1 > >> smmu execute cmd0 > >> poll timeout, because msidata=1 is overridden by > >> cmd0, that means VAL=0, sync_idx=1. > > > > Oh yuck, you're right! We probably want a CC stable on this. Did you see > > this go wrong in practice? > Just misreported and make the caller wait for a long time until TIMEOUT. It's > rare to happen, because any other CMD_SYNC during the waiting period will break > it. Thanks. Please mention that in the commit message, because I think it's useful to know. > >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > >> --- > >> drivers/iommu/arm-smmu-v3.c | 7 +++---- > >> 1 file changed, 3 insertions(+), 4 deletions(-) > >> > >> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c > >> index 1d64710..4810f61 100644 > >> --- a/drivers/iommu/arm-smmu-v3.c > >> +++ b/drivers/iommu/arm-smmu-v3.c > >> @@ -566,7 +566,7 @@ struct arm_smmu_device { > >> > >> int gerr_irq; > >> int combined_irq; > >> - atomic_t sync_nr; > >> + u32 sync_nr; > >> > >> unsigned long ias; /* IPA */ > >> unsigned long oas; /* PA */ > >> @@ -836,7 +836,6 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) > >> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV); > >> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH); > >> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB); > >> - cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent->sync.msidata); > >> cmd[1] |= ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK; > >> break; > >> default: > >> @@ -947,7 +946,6 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) > >> struct arm_smmu_cmdq_ent ent = { > >> .opcode = CMDQ_OP_CMD_SYNC, > >> .sync = { > >> - .msidata = atomic_inc_return_relaxed(&smmu->sync_nr), > >> .msiaddr = virt_to_phys(&smmu->sync_count), > >> }, > >> }; > >> @@ -955,6 +953,8 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) > >> arm_smmu_cmdq_build_cmd(cmd, &ent); > >> > >> spin_lock_irqsave(&smmu->cmdq.lock, flags); > >> + ent.sync.msidata = ++smmu->sync_nr; > >> + cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent.sync.msidata); > > > > I really don't like splitting this out from building the rest of the > > command. Can you just move the call to arm_smmu_cmdq_build_cmd into the > > critical section, please? > OK. I have considered that before, just worry it will increase the > compition of spinlock. If you can provide numbers showing that it's a problem, then we could add a helper function e.g. arm_smmu_cmdq_sync_set_msidata(arm_smmu_cmdq_ent *cmd) > In addition, I will append a optimization patch: the adjacent CMD_SYNCs, > we only need one. Ok, but please keep them separate, since I don't want to fix up fixes and optimisations. Thanks, Will ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 1/1] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout 2018-08-09 8:49 ` Will Deacon @ 2018-08-09 10:05 ` Leizhen (ThunderTown) 0 siblings, 0 replies; 5+ messages in thread From: Leizhen (ThunderTown) @ 2018-08-09 10:05 UTC (permalink / raw) To: linux-arm-kernel On 2018/8/9 16:49, Will Deacon wrote: > On Thu, Aug 09, 2018 at 09:30:51AM +0800, Leizhen (ThunderTown) wrote: >> On 2018/8/8 18:12, Will Deacon wrote: >>> On Mon, Aug 06, 2018 at 08:31:29PM +0800, Zhen Lei wrote: >>>> The condition "(int)(VAL - sync_idx) >= 0" to break loop in function >>>> __arm_smmu_sync_poll_msi requires that sync_idx must be increased >>>> monotonously according to the sequence of the CMDs in the cmdq. >>>> >>>> But ".msidata = atomic_inc_return_relaxed(&smmu->sync_nr)" is not protected >>>> by spinlock, so the following scenarios may appear: >>>> cpu0 cpu1 >>>> msidata=0 >>>> msidata=1 >>>> insert cmd1 >>>> insert cmd0 >>>> smmu execute cmd1 >>>> smmu execute cmd0 >>>> poll timeout, because msidata=1 is overridden by >>>> cmd0, that means VAL=0, sync_idx=1. >>> >>> Oh yuck, you're right! We probably want a CC stable on this. Did you see >>> this go wrong in practice? >> Just misreported and make the caller wait for a long time until TIMEOUT. It's >> rare to happen, because any other CMD_SYNC during the waiting period will break >> it. > > Thanks. Please mention that in the commit message, because I think it's > useful to know. OK. > >>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >>>> --- >>>> drivers/iommu/arm-smmu-v3.c | 7 +++---- >>>> 1 file changed, 3 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c >>>> index 1d64710..4810f61 100644 >>>> --- a/drivers/iommu/arm-smmu-v3.c >>>> +++ b/drivers/iommu/arm-smmu-v3.c >>>> @@ -566,7 +566,7 @@ struct arm_smmu_device { >>>> >>>> int gerr_irq; >>>> int combined_irq; >>>> - atomic_t sync_nr; >>>> + u32 sync_nr; >>>> >>>> unsigned long ias; /* IPA */ >>>> unsigned long oas; /* PA */ >>>> @@ -836,7 +836,6 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) >>>> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV); >>>> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH); >>>> cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB); >>>> - cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent->sync.msidata); >>>> cmd[1] |= ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK; >>>> break; >>>> default: >>>> @@ -947,7 +946,6 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) >>>> struct arm_smmu_cmdq_ent ent = { >>>> .opcode = CMDQ_OP_CMD_SYNC, >>>> .sync = { >>>> - .msidata = atomic_inc_return_relaxed(&smmu->sync_nr), >>>> .msiaddr = virt_to_phys(&smmu->sync_count), >>>> }, >>>> }; >>>> @@ -955,6 +953,8 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) >>>> arm_smmu_cmdq_build_cmd(cmd, &ent); >>>> >>>> spin_lock_irqsave(&smmu->cmdq.lock, flags); >>>> + ent.sync.msidata = ++smmu->sync_nr; >>>> + cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent.sync.msidata); >>> >>> I really don't like splitting this out from building the rest of the >>> command. Can you just move the call to arm_smmu_cmdq_build_cmd into the >>> critical section, please? >> OK. I have considered that before, just worry it will increase the >> compition of spinlock. > > If you can provide numbers showing that it's a problem, then we could add > a helper function e.g. arm_smmu_cmdq_sync_set_msidata(arm_smmu_cmdq_ent *cmd) The performance data from my current test envirnoment is not stable now, I'm trying to find anothor one. So I want to leave this problem for the time being. If it'a problem, I will send a new patch. > >> In addition, I will append a optimization patch: the adjacent CMD_SYNCs, >> we only need one. > > Ok, but please keep them separate, since I don't want to fix up fixes and > optimisations. OK > > Thanks, > > Will > > . > -- Thanks! BestRegards ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2018-08-09 10:05 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2018-08-06 12:31 [PATCH 1/1] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout Zhen Lei 2018-08-08 10:12 ` Will Deacon 2018-08-09 1:30 ` Leizhen (ThunderTown) 2018-08-09 8:49 ` Will Deacon 2018-08-09 10:05 ` Leizhen (ThunderTown)
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