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    Subject[PATCH] mm/fork: Clear PASID for new mm
    Date
    From: Fenghua Yu <fenghua.yu@intel.com>

    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.

    Reviewed-by: Tony Luck <tony.luck@intel.com>
    Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
    Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
    ---
    This patch was part of the series introducing mm->pasid, but got lost
    along the way [1]. It still makes sense to have it, because each address
    space has a different PASID. And the IOMMU code in iommu_sva_alloc_pasid()
    expects the pasid field of a new mm struct to be cleared.

    [1] https://lore.kernel.org/linux-iommu/YDgh53AcQHT+T3L0@otcwcpicx3.sc.intel.com/
    ---
    include/linux/mm_types.h | 1 +
    kernel/fork.c | 8 ++++++++
    2 files changed, 9 insertions(+)

    diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
    index 0974ad501a47..6613b26a8894 100644
    --- a/include/linux/mm_types.h
    +++ b/include/linux/mm_types.h
    @@ -23,6 +23,7 @@
    #endif
    #define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))

    +#define INIT_PASID 0

    struct address_space;
    struct mem_cgroup;
    diff --git a/kernel/fork.c b/kernel/fork.c
    index d66cd1014211..808af2cc8ab6 100644
    --- a/kernel/fork.c
    +++ b/kernel/fork.c
    @@ -994,6 +994,13 @@ 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
    @@ -1024,6 +1031,7 @@ 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);
    --
    2.30.1
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