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authorDavid Rientjes <rientjes@google.com>2020-08-25 12:56:28 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2020-09-11 13:24:15 -0400
commit7be74942f184fdfba34ddd19a0d995deb34d4a03 (patch)
tree4654fda81c153ae10d85a5798e8ca3ebb007b570
parent15e9e35cd1dec2bc138464de6bf8ef828df19235 (diff)
downloadlinux-sh-7be74942f184fdfba34ddd19a0d995deb34d4a03.tar.gz
KVM: SVM: Periodically schedule when unregistering regions on destroy
There may be many encrypted regions that need to be unregistered when a SEV VM is destroyed. This can lead to soft lockups. For example, on a host running 4.15: watchdog: BUG: soft lockup - CPU#206 stuck for 11s! [t_virtual_machi:194348] CPU: 206 PID: 194348 Comm: t_virtual_machi RIP: 0010:free_unref_page_list+0x105/0x170 ... Call Trace: [<0>] release_pages+0x159/0x3d0 [<0>] sev_unpin_memory+0x2c/0x50 [kvm_amd] [<0>] __unregister_enc_region_locked+0x2f/0x70 [kvm_amd] [<0>] svm_vm_destroy+0xa9/0x200 [kvm_amd] [<0>] kvm_arch_destroy_vm+0x47/0x200 [<0>] kvm_put_kvm+0x1a8/0x2f0 [<0>] kvm_vm_release+0x25/0x30 [<0>] do_exit+0x335/0xc10 [<0>] do_group_exit+0x3f/0xa0 [<0>] get_signal+0x1bc/0x670 [<0>] do_signal+0x31/0x130 Although the CLFLUSH is no longer issued on every encrypted region to be unregistered, there are no other changes that can prevent soft lockups for very large SEV VMs in the latest kernel. Periodically schedule if necessary. This still holds kvm->lock across the resched, but since this only happens when the VM is destroyed this is assumed to be acceptable. Signed-off-by: David Rientjes <rientjes@google.com> Message-Id: <alpine.DEB.2.23.453.2008251255240.2987727@chino.kir.corp.google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/svm/sev.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 402dc4234e39..7bf7bf734979 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1106,6 +1106,7 @@ void sev_vm_destroy(struct kvm *kvm)
list_for_each_safe(pos, q, head) {
__unregister_enc_region_locked(kvm,
list_entry(pos, struct enc_region, list));
+ cond_resched();
}
}