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    Subject[PATCH 5.4 091/118] iommu/vt-d: Silence RCU-list debugging warning in dmar_find_atsr()
    Date
    From: Qian Cai <cai@lca.pw>

    [ Upstream commit c6f4ebdeba4cff590594df931ff1ee610c426431 ]

    dmar_find_atsr() calls list_for_each_entry_rcu() outside of an RCU read
    side critical section but with dmar_global_lock held. Silence this
    false positive.

    drivers/iommu/intel-iommu.c:4504 RCU-list traversed in non-reader section!!
    1 lock held by swapper/0/1:
    #0: ffffffff9755bee8 (dmar_global_lock){+.+.}, at: intel_iommu_init+0x1a6/0xe19

    Call Trace:
    dump_stack+0xa4/0xfe
    lockdep_rcu_suspicious+0xeb/0xf5
    dmar_find_atsr+0x1ab/0x1c0
    dmar_parse_one_atsr+0x64/0x220
    dmar_walk_remapping_entries+0x130/0x380
    dmar_table_init+0x166/0x243
    intel_iommu_init+0x1ab/0xe19
    pci_iommu_init+0x1a/0x44
    do_one_initcall+0xae/0x4d0
    kernel_init_freeable+0x412/0x4c5
    kernel_init+0x19/0x193

    Signed-off-by: Qian Cai <cai@lca.pw>
    Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/iommu/intel-iommu.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
    index 0d922eeae3579..773ac2b0d6068 100644
    --- a/drivers/iommu/intel-iommu.c
    +++ b/drivers/iommu/intel-iommu.c
    @@ -4335,7 +4335,8 @@ static struct dmar_atsr_unit *dmar_find_atsr(struct acpi_dmar_atsr *atsr)
    struct dmar_atsr_unit *atsru;
    struct acpi_dmar_atsr *tmp;

    - list_for_each_entry_rcu(atsru, &dmar_atsr_units, list) {
    + list_for_each_entry_rcu(atsru, &dmar_atsr_units, list,
    + dmar_rcu_check()) {
    tmp = (struct acpi_dmar_atsr *)atsru->hdr;
    if (atsr->segment != tmp->segment)
    continue;
    --
    2.20.1


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