Messages in this thread | | | Date | Wed, 24 Feb 2021 11:19:27 +0100 | From | Jean-Philippe Brucker <> | Subject | Re: [PATCH v6 08/12] fork: Clear PASID for new mm |
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Hi Fenghua,
[Trimmed the Cc list]
On Mon, Jul 13, 2020 at 04:48:03PM -0700, Fenghua Yu wrote: > When a new mm is created, its PASID should be cleared, i.e. the PASID is > initialized to its init state 0 on both ARM and X86.
I just noticed this patch was dropped in v7, and am wondering whether we could still upstream it. Does x86 need a child with a new address space (!CLONE_VM) to inherit the PASID of the parent? That doesn't make much sense with regard to IOMMU structures - same PASID indexing multiple PGDs?
Currently iommu_sva_alloc_pasid() assumes mm->pasid is always initialized to 0 and fails on forked tasks. I'm trying to figure out how to fix this. Could we clear the pasid on fork or does it break the x86 model?
Thanks, Jean
> > Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> > Reviewed-by: Tony Luck <tony.luck@intel.com> > --- > v2: > - Add this patch to initialize PASID value for a new mm. > > include/linux/mm_types.h | 2 ++ > kernel/fork.c | 8 ++++++++ > 2 files changed, 10 insertions(+) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index d61285cfe027..d60d2ec10881 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -22,6 +22,8 @@ > #endif > #define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1)) > > +/* Initial PASID value is 0. */ > +#define INIT_PASID 0 > > struct address_space; > struct mem_cgroup; > diff --git a/kernel/fork.c b/kernel/fork.c > index 142b23645d82..43b5f112604d 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1007,6 +1007,13 @@ static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) > #endif > } > > +static void mm_init_pasid(struct mm_struct *mm) > +{ > +#ifdef CONFIG_IOMMU_SUPPORT > + mm->pasid = INIT_PASID; > +#endif > +} > + > static void mm_init_uprobes_state(struct mm_struct *mm) > { > #ifdef CONFIG_UPROBES > @@ -1035,6 +1042,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, > mm_init_cpumask(mm); > mm_init_aio(mm); > mm_init_owner(mm, p); > + mm_init_pasid(mm); > RCU_INIT_POINTER(mm->exe_file, NULL); > mmu_notifier_subscriptions_init(mm); > init_tlb_flush_pending(mm); > -- > 2.19.1 >
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