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author | Will Deacon <will@kernel.org> | 2020-08-11 11:27:25 +0100 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-08-21 18:06:43 -0400 |
commit | b5331379bc62611d1026173a09c73573384201d9 (patch) | |
tree | 363d000f8537f91bbdd9c82f2d56738094ebe0d7 /arch/arm64/kvm/mmu.c | |
parent | fdfe7cbd58806522e799e2a50a15aee7f2cbb7b6 (diff) | |
download | linux-b5331379bc62611d1026173a09c73573384201d9.tar.gz linux-b5331379bc62611d1026173a09c73573384201d9.tar.bz2 linux-b5331379bc62611d1026173a09c73573384201d9.zip |
KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set
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>
Diffstat (limited to 'arch/arm64/kvm/mmu.c')
-rw-r--r-- | arch/arm64/kvm/mmu.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index dc351802ff18..ba00bcc0c884 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -343,7 +343,8 @@ static void unmap_stage2_p4ds(struct kvm_s2_mmu *mmu, 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_s2_mmu *mmu, phys_addr_t start, u64 size) +static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size, + bool may_block) { struct kvm *kvm = mmu->kvm; pgd_t *pgd; @@ -369,11 +370,16 @@ static void unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 si * 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_s2_mmu *mmu, phys_addr_t start, u64 size) +{ + __unmap_stage2_range(mmu, start, size, true); +} + static void stage2_flush_ptes(struct kvm_s2_mmu *mmu, pmd_t *pmd, phys_addr_t addr, phys_addr_t end) { @@ -2208,7 +2214,10 @@ 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->arch.mmu, gpa, size); + unsigned flags = *(unsigned *)data; + bool may_block = flags & MMU_NOTIFIER_RANGE_BLOCKABLE; + + __unmap_stage2_range(&kvm->arch.mmu, gpa, size, may_block); return 0; } @@ -2219,7 +2228,7 @@ 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; } |