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Date:   Mon, 1 Mar 2021 09:22:15 -0800
From:   Ben Gardon <bgardon@...gle.com>
To:     kernel test robot <lkp@...el.com>
Cc:     kbuild-all@...ts.01.org, LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Feiner <pfeiner@...gle.com>
Subject: Re: arch/x86/kvm/mmu/tdp_mmu.c:533:9: sparse: sparse: cast removes
 address space '__rcu' of expression

It looks like the __rcu tags aren't being propagated around to all the
different references to PT memory. I'll look into what it would take
to fix this. I don't believe these kernel test warnings indicate a
correctness issue in the kernel, but propagating the __rcu annotations
will be helpful for developers in the future.

On Sat, Feb 27, 2021 at 3:48 PM kernel test robot <lkp@...el.com> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   5695e51619745d4fe3ec2506a2f0cd982c5e27a4
> commit: 08f07c800e9d35b59d0c8346333f189160bd67d4 KVM: x86/mmu: Flush TLBs after zap in TDP MMU PF handler
> date:   3 weeks ago
> config: x86_64-randconfig-s022-20210228 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
> reproduce:
>         # apt-get install sparse
>         # sparse version: v0.6.3-241-geaceeafa-dirty
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=08f07c800e9d35b59d0c8346333f189160bd67d4
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout 08f07c800e9d35b59d0c8346333f189160bd67d4
>         # save the attached .config to linux build tree
>         make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=x86_64
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
>
> "sparse warnings: (new ones prefixed by >>)"
>    arch/x86/kvm/mmu/tdp_mmu.c:459:49: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected unsigned long long [usertype] *pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:459:49: sparse:     expected unsigned long long [usertype] *pt
>    arch/x86/kvm/mmu/tdp_mmu.c:459:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *
>    arch/x86/kvm/mmu/tdp_mmu.c:291:9: sparse: sparse: context imbalance in 'tdp_mmu_link_page' - different lock contexts for basic block
>    arch/x86/kvm/mmu/tdp_mmu.c:316:9: sparse: sparse: context imbalance in 'tdp_mmu_unlink_page' - different lock contexts for basic block
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected unsigned long long [usertype] *root_pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     expected unsigned long long [usertype] *root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     got unsigned long long [noderef] [usertype] __rcu *
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected unsigned long long [usertype] *root_pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse:     expected unsigned long long [usertype] *root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse:     got unsigned long long [noderef] [usertype] __rcu *
> >> arch/x86/kvm/mmu/tdp_mmu.c:533:9: sparse: sparse: cast removes address space '__rcu' of expression
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected unsigned long long [usertype] *root_pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse:     expected unsigned long long [usertype] *root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse:     got unsigned long long [noderef] [usertype] __rcu *
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected unsigned long long [usertype] *root_pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse:     expected unsigned long long [usertype] *root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:487:40: sparse:     got unsigned long long [noderef] [usertype] __rcu *
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected unsigned long long [usertype] *root_pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     expected unsigned long long [usertype] *root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     got unsigned long long [noderef] [usertype] __rcu *
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected unsigned long long [usertype] *root_pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     expected unsigned long long [usertype] *root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     got unsigned long long [noderef] [usertype] __rcu *
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected unsigned long long [usertype] *root_pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     expected unsigned long long [usertype] *root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     got unsigned long long [noderef] [usertype] __rcu *
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected unsigned long long [usertype] *root_pt @@     got unsigned long long [noderef] [usertype] __rcu * @@
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     expected unsigned long long [usertype] *root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:654:51: sparse:     got unsigned long long [noderef] [usertype] __rcu *
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected unsigned long long [usertype] *sptep @@     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt @@
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     expected unsigned long long [usertype] *sptep
>    arch/x86/kvm/mmu/tdp_mmu.c:560:49: sparse:     got unsigned long long [noderef] [usertype] __rcu *[usertype] root_pt
>
> vim +/__rcu +533 arch/x86/kvm/mmu/tdp_mmu.c
>
>    509
>    510  static inline bool tdp_mmu_zap_spte_atomic(struct kvm *kvm,
>    511                                             struct tdp_iter *iter)
>    512  {
>    513          /*
>    514           * Freeze the SPTE by setting it to a special,
>    515           * non-present value. This will stop other threads from
>    516           * immediately installing a present entry in its place
>    517           * before the TLBs are flushed.
>    518           */
>    519          if (!tdp_mmu_set_spte_atomic(kvm, iter, REMOVED_SPTE))
>    520                  return false;
>    521
>    522          kvm_flush_remote_tlbs_with_address(kvm, iter->gfn,
>    523                                             KVM_PAGES_PER_HPAGE(iter->level));
>    524
>    525          /*
>    526           * No other thread can overwrite the removed SPTE as they
>    527           * must either wait on the MMU lock or use
>    528           * tdp_mmu_set_spte_atomic which will not overrite the
>    529           * special removed SPTE value. No bookkeeping is needed
>    530           * here since the SPTE is going from non-present
>    531           * to non-present.
>    532           */
>  > 533          WRITE_ONCE(*iter->sptep, 0);
>    534
>    535          return true;
>    536  }
>    537
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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