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authorWill Deacon <will@kernel.org>2020-08-11 11:27:25 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-08-26 10:41:08 +0200
commitd316d52742c48cffb94f3aca02945706097e143a (patch)
treec7b9cdbcf68ca382ddd5ec593b5929f49e5e4d30
parente1818ffcca0ea32d541ed554a44bb1de975ab8fa (diff)
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KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set
commit b5331379bc62611d1026173a09c73573384201d9 upstream. When an MMU notifier call results in unmapping a range that spans multiple PGDs, we end up calling into cond_resched_lock() when crossing a PGD boundary, since this avoids running into RCU stalls during VM teardown. Unfortunately, if the VM is destroyed as a result of OOM, then blocking is not permitted and the call to the scheduler triggers the following BUG(): | BUG: sleeping function called from invalid context at arch/arm64/kvm/mmu.c:394 | in_atomic(): 1, irqs_disabled(): 0, non_block: 1, pid: 36, name: oom_reaper | INFO: lockdep is turned off. | CPU: 3 PID: 36 Comm: oom_reaper Not tainted 5.8.0 #1 | Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 | Call trace: | dump_backtrace+0x0/0x284 | show_stack+0x1c/0x28 | dump_stack+0xf0/0x1a4 | ___might_sleep+0x2bc/0x2cc | unmap_stage2_range+0x160/0x1ac | kvm_unmap_hva_range+0x1a0/0x1c8 | kvm_mmu_notifier_invalidate_range_start+0x8c/0xf8 | __mmu_notifier_invalidate_range_start+0x218/0x31c | mmu_notifier_invalidate_range_start_nonblock+0x78/0xb0 | __oom_reap_task_mm+0x128/0x268 | oom_reap_task+0xac/0x298 | oom_reaper+0x178/0x17c | kthread+0x1e4/0x1fc | ret_from_fork+0x10/0x30 Use the new 'flags' argument to kvm_unmap_hva_range() to ensure that we only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is set in the notifier flags. Cc: <stable@vger.kernel.org> Fixes: 8b3405e345b5 ("kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd") Cc: Marc Zyngier <maz@kernel.org> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: James Morse <james.morse@arm.com> Signed-off-by: Will Deacon <will@kernel.org> Message-Id: <20200811102725.7121-3-will@kernel.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--virt/kvm/arm/mmu.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index b4a6bbadd144..7501ec8a4600 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -332,7 +332,8 @@ static void unmap_stage2_puds(struct kvm *kvm, pgd_t *pgd,
* destroying the VM), otherwise another faulting VCPU may come in and mess
* with things behind our backs.
*/
-static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
+static void __unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size,
+ bool may_block)
{
pgd_t *pgd;
phys_addr_t addr = start, end = start + size;
@@ -357,11 +358,16 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
* If the range is too large, release the kvm->mmu_lock
* to prevent starvation and lockup detector warnings.
*/
- if (next != end)
+ if (may_block && next != end)
cond_resched_lock(&kvm->mmu_lock);
} while (pgd++, addr = next, addr != end);
}
+static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
+{
+ __unmap_stage2_range(kvm, start, size, true);
+}
+
static void stage2_flush_ptes(struct kvm *kvm, pmd_t *pmd,
phys_addr_t addr, phys_addr_t end)
{
@@ -2045,7 +2051,10 @@ static int handle_hva_to_gpa(struct kvm *kvm,
static int kvm_unmap_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data)
{
- unmap_stage2_range(kvm, gpa, size);
+ unsigned flags = *(unsigned *)data;
+ bool may_block = flags & MMU_NOTIFIER_RANGE_BLOCKABLE;
+
+ __unmap_stage2_range(kvm, gpa, size, may_block);
return 0;
}
@@ -2056,7 +2065,7 @@ int kvm_unmap_hva_range(struct kvm *kvm,
return 0;
trace_kvm_unmap_hva_range(start, end);
- handle_hva_to_gpa(kvm, start, end, &kvm_unmap_hva_handler, NULL);
+ handle_hva_to_gpa(kvm, start, end, &kvm_unmap_hva_handler, &flags);
return 0;
}