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Message-ID: <202104012131.qcIIr4tP-lkp@intel.com>
Date: Thu, 1 Apr 2021 21:16:05 +0800
From: kernel test robot <lkp@...el.com>
To: Ben Gardon <bgardon@...gle.com>, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: kbuild-all@...ts.01.org, Paolo Bonzini <pbonzini@...hat.com>,
Peter Xu <peterx@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
Peter Shier <pshier@...gle.com>,
Peter Feiner <pfeiner@...gle.com>,
Junaid Shahid <junaids@...gle.com>,
Jim Mattson <jmattson@...gle.com>,
Yulei Zhang <yulei.kernel@...il.com>
Subject: Re: [PATCH 08/13] KVM: x86/mmu: Protect the tdp_mmu_roots list with
RCU
Hi Ben,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on next-20210331]
[cannot apply to kvm/queue tip/master linux/master linus/master v5.12-rc5 v5.12-rc4 v5.12-rc3 v5.12-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Ben-Gardon/More-parallel-operations-for-the-TDP-MMU/20210401-051137
base: 7a43c78d0573e0bbbb0456b033e2b9a895b89464
config: x86_64-allyesconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
# https://github.com/0day-ci/linux/commit/2b2c6d3bdc35269df5f9293a02da5b71c74095f3
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Ben-Gardon/More-parallel-operations-for-the-TDP-MMU/20210401-051137
git checkout 2b2c6d3bdc35269df5f9293a02da5b71c74095f3
# save the attached .config to linux build tree
make W=1 ARCH=x86_64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
All errors (new ones prefixed by >>):
In file included from include/linux/rculist.h:11,
from include/linux/pid.h:5,
from include/linux/sched.h:14,
from include/linux/hardirq.h:9,
from include/linux/kvm_host.h:7,
from arch/x86/kvm/mmu.h:5,
from arch/x86/kvm/mmu/tdp_mmu.c:3:
arch/x86/kvm/mmu/tdp_mmu.c: In function 'kvm_tdp_mmu_get_vcpu_root_hpa':
>> arch/x86/kvm/mmu/tdp_mmu.c:139:5: error: implicit declaration of function 'lockdep_is_held_write'; did you mean 'lockdep_is_held_type'? [-Werror=implicit-function-declaration]
139 | lockdep_is_held_write(&kvm->mmu_lock))
| ^~~~~~~~~~~~~~~~~~~~~
include/linux/rcupdate.h:318:52: note: in definition of macro 'RCU_LOCKDEP_WARN'
318 | if (debug_lockdep_rcu_enabled() && !__warned && (c)) { \
| ^
include/linux/rculist.h:391:7: note: in expansion of macro '__list_check_rcu'
391 | for (__list_check_rcu(dummy, ## cond, 0), \
| ^~~~~~~~~~~~~~~~
arch/x86/kvm/mmu/tdp_mmu.c:138:2: note: in expansion of macro 'list_for_each_entry_rcu'
138 | list_for_each_entry_rcu(_root, &_kvm->arch.tdp_mmu_roots, link, \
| ^~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kvm/mmu/tdp_mmu.c:184:2: note: in expansion of macro 'for_each_tdp_mmu_root'
184 | for_each_tdp_mmu_root(kvm, root) {
| ^~~~~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
vim +139 arch/x86/kvm/mmu/tdp_mmu.c
2
> 3 #include "mmu.h"
4 #include "mmu_internal.h"
5 #include "mmutrace.h"
6 #include "tdp_iter.h"
7 #include "tdp_mmu.h"
8 #include "spte.h"
9
10 #include <asm/cmpxchg.h>
11 #include <trace/events/kvm.h>
12
13 static bool __read_mostly tdp_mmu_enabled = false;
14 module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0644);
15
16 /* Initializes the TDP MMU for the VM, if enabled. */
17 void kvm_mmu_init_tdp_mmu(struct kvm *kvm)
18 {
19 if (!tdp_enabled || !READ_ONCE(tdp_mmu_enabled))
20 return;
21
22 /* This should not be changed for the lifetime of the VM. */
23 kvm->arch.tdp_mmu_enabled = true;
24
25 INIT_LIST_HEAD(&kvm->arch.tdp_mmu_roots);
26 spin_lock_init(&kvm->arch.tdp_mmu_pages_lock);
27 INIT_LIST_HEAD(&kvm->arch.tdp_mmu_pages);
28 }
29
30 void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
31 {
32 if (!kvm->arch.tdp_mmu_enabled)
33 return;
34
35 WARN_ON(!list_empty(&kvm->arch.tdp_mmu_roots));
36
37 /*
38 * Ensure that all the outstanding RCU callbacks to free shadow pages
39 * can run before the VM is torn down.
40 */
41 rcu_barrier();
42 }
43
44 static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
45 gfn_t start, gfn_t end, bool can_yield);
46
47 static void tdp_mmu_free_sp(struct kvm_mmu_page *sp)
48 {
49 free_page((unsigned long)sp->spt);
50 kmem_cache_free(mmu_page_header_cache, sp);
51 }
52
53 /*
54 * This is called through call_rcu in order to free TDP page table memory
55 * safely with respect to other kernel threads that may be operating on
56 * the memory.
57 * By only accessing TDP MMU page table memory in an RCU read critical
58 * section, and freeing it after a grace period, lockless access to that
59 * memory won't use it after it is freed.
60 */
61 static void tdp_mmu_free_sp_rcu_callback(struct rcu_head *head)
62 {
63 struct kvm_mmu_page *sp = container_of(head, struct kvm_mmu_page,
64 rcu_head);
65
66 tdp_mmu_free_sp(sp);
67 }
68
69 void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root)
70 {
71 gfn_t max_gfn = 1ULL << (shadow_phys_bits - PAGE_SHIFT);
72
73 lockdep_assert_held_write(&kvm->mmu_lock);
74
75 if (!refcount_dec_and_test(&root->tdp_mmu_root_count))
76 return;
77
78 WARN_ON(!root->tdp_mmu_page);
79
80 spin_lock(&kvm->arch.tdp_mmu_pages_lock);
81 list_del_rcu(&root->link);
82 spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
83
84 zap_gfn_range(kvm, root, 0, max_gfn, false);
85
86 call_rcu(&root->rcu_head, tdp_mmu_free_sp_rcu_callback);
87 }
88
89 /*
90 * Finds the next valid root after root (or the first valid root if root
91 * is NULL), takes a reference on it, and returns that next root. If root
92 * is not NULL, this thread should have already taken a reference on it, and
93 * that reference will be dropped. If no valid root is found, this
94 * function will return NULL.
95 */
96 static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
97 struct kvm_mmu_page *prev_root)
98 {
99 struct kvm_mmu_page *next_root;
100
101 lockdep_assert_held_write(&kvm->mmu_lock);
102
103 rcu_read_lock();
104
105 if (prev_root)
106 next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
107 &prev_root->link,
108 typeof(*prev_root), link);
109 else
110 next_root = list_first_or_null_rcu(&kvm->arch.tdp_mmu_roots,
111 typeof(*next_root), link);
112
113 while (next_root && !kvm_tdp_mmu_get_root(kvm, next_root))
114 next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
115 &next_root->link, typeof(*next_root), link);
116
117 rcu_read_unlock();
118
119 if (prev_root)
120 kvm_tdp_mmu_put_root(kvm, prev_root);
121
122 return next_root;
123 }
124
125 /*
126 * Note: this iterator gets and puts references to the roots it iterates over.
127 * This makes it safe to release the MMU lock and yield within the loop, but
128 * if exiting the loop early, the caller must drop the reference to the most
129 * recent root. (Unless keeping a live reference is desirable.)
130 */
131 #define for_each_tdp_mmu_root_yield_safe(_kvm, _root) \
132 for (_root = tdp_mmu_next_root(_kvm, NULL); \
133 _root; \
134 _root = tdp_mmu_next_root(_kvm, _root))
135
136 /* Only safe under the MMU lock in write mode, without yielding. */
137 #define for_each_tdp_mmu_root(_kvm, _root) \
138 list_for_each_entry_rcu(_root, &_kvm->arch.tdp_mmu_roots, link, \
> 139 lockdep_is_held_write(&kvm->mmu_lock))
140
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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