From: Radim Krcmar Date: Wed, 14 Aug 2019 03:37:37 +0000 (-0400) Subject: kvm: x86: skip populating logical dest map if apic is not sw enabled X-Git-Tag: v5.15~5513^2~51 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b14c876b994f208b6b95c222056e1deb0a45de0e;p=platform%2Fkernel%2Flinux-starfive.git kvm: x86: skip populating logical dest map if apic is not sw enabled 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 --- diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 685d17c..e904ff0 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -216,6 +216,9 @@ 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)) { @@ -258,6 +261,8 @@ static inline void apic_set_spiv(struct kvm_lapic *apic, u32 val) static_key_slow_dec_deferred(&apic_sw_disabled); else static_key_slow_inc(&apic_sw_disabled.key); + + recalculate_apic_map(apic->vcpu->kvm); } }