From 5b8daaf8a4afd3425bebf014410644eb8aa0e343 Mon Sep 17 00:00:00 2001 From: Radim Krcmar Date: Mon, 9 Sep 2019 15:23:53 +0800 Subject: [PATCH] kvm: x86: skip populating logical dest map if apic is not sw enabled commit b14c876b994f208b6b95c222056e1deb0a45de0e upstream. recalculate_apic_map does not santize ldr and it's possible that multiple bits are set. In that case, a previous valid entry can potentially be overwritten by an invalid one. This condition is hit when booting a 32 bit, >8 CPU, RHEL6 guest and then triggering a crash to boot a kdump kernel. This is the sequence of events: 1. Linux boots in bigsmp mode and enables PhysFlat, however, it still writes to the LDR which probably will never be used. 2. However, when booting into kdump, the stale LDR values remain as they are not cleared by the guest and there isn't a apic reset. 3. kdump boots with 1 cpu, and uses Logical Destination Mode but the logical map has been overwritten and points to an inactive vcpu. Signed-off-by: Radim Krcmar Signed-off-by: Bandan Das Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang --- arch/x86/kvm/lapic.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 031bd7f91f98..5f5bc5976804 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -209,6 +209,9 @@ static void recalculate_apic_map(struct kvm *kvm) if (!apic_x2apic_mode(apic) && !new->phys_map[xapic_id]) new->phys_map[xapic_id] = apic; + if (!kvm_apic_sw_enabled(apic)) + continue; + ldr = kvm_lapic_get_reg(apic, APIC_LDR); if (apic_x2apic_mode(apic)) { @@ -252,6 +255,8 @@ static inline void apic_set_spiv(struct kvm_lapic *apic, u32 val) recalculate_apic_map(apic->vcpu->kvm); } else static_key_slow_inc(&apic_sw_disabled.key); + + recalculate_apic_map(apic->vcpu->kvm); } } -- GitLab