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authorDavid Woodhouse <dwmw@amazon.co.uk>2021-10-26 06:12:38 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2021-10-28 17:45:38 +0300
commitf3d1436d4bf8ced1c9a62a045d193a65567e1fcc (patch)
tree74e43ee5d3a5440abd09d6ce306651f3ad515e9b
parent9b0971ca7fc75daca80c0bb6c02e96059daea90a (diff)
downloadlinux-f3d1436d4bf8ced1c9a62a045d193a65567e1fcc.tar.xz
KVM: x86: Take srcu lock in post_kvm_run_save()
The Xen interrupt injection for event channels relies on accessing the guest's vcpu_info structure in __kvm_xen_has_interrupt(), through a gfn_to_hva_cache. This requires the srcu lock to be held, which is mostly the case except for this code path: [ 11.822877] WARNING: suspicious RCU usage [ 11.822965] ----------------------------- [ 11.823013] include/linux/kvm_host.h:664 suspicious rcu_dereference_check() usage! [ 11.823131] [ 11.823131] other info that might help us debug this: [ 11.823131] [ 11.823196] [ 11.823196] rcu_scheduler_active = 2, debug_locks = 1 [ 11.823253] 1 lock held by dom:0/90: [ 11.823292] #0: ffff998956ec8118 (&vcpu->mutex){+.+.}, at: kvm_vcpu_ioctl+0x85/0x680 [ 11.823379] [ 11.823379] stack backtrace: [ 11.823428] CPU: 2 PID: 90 Comm: dom:0 Kdump: loaded Not tainted 5.4.34+ #5 [ 11.823496] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 [ 11.823612] Call Trace: [ 11.823645] dump_stack+0x7a/0xa5 [ 11.823681] lockdep_rcu_suspicious+0xc5/0x100 [ 11.823726] __kvm_xen_has_interrupt+0x179/0x190 [ 11.823773] kvm_cpu_has_extint+0x6d/0x90 [ 11.823813] kvm_cpu_accept_dm_intr+0xd/0x40 [ 11.823853] kvm_vcpu_ready_for_interrupt_injection+0x20/0x30 < post_kvm_run_save() inlined here > [ 11.823906] kvm_arch_vcpu_ioctl_run+0x135/0x6a0 [ 11.823947] kvm_vcpu_ioctl+0x263/0x680 Fixes: 40da8ccd724f ("KVM: x86/xen: Add event channel interrupt vector upcall") Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Cc: stable@vger.kernel.org Message-Id: <606aaaf29fca3850a63aa4499826104e77a72346.camel@infradead.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/x86.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5c82eff19e4a..ffd9dd7d5d14 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8783,9 +8783,17 @@ static void post_kvm_run_save(struct kvm_vcpu *vcpu)
kvm_run->cr8 = kvm_get_cr8(vcpu);
kvm_run->apic_base = kvm_get_apic_base(vcpu);
+
+ /*
+ * The call to kvm_ready_for_interrupt_injection() may end up in
+ * kvm_xen_has_interrupt() which may require the srcu lock to be
+ * held, to protect against changes in the vcpu_info address.
+ */
+ vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
kvm_run->ready_for_interrupt_injection =
pic_in_kernel(vcpu->kvm) ||
kvm_vcpu_ready_for_interrupt_injection(vcpu);
+ srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
if (is_smm(vcpu))
kvm_run->flags |= KVM_RUN_X86_SMM;