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From: Nitesh Narayan Lal <nitesh@redhat.com> To: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mtosatti@redhat.com, vkuznets@redhat.com, sean.j.christopherson@intel.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org Subject: Re: [Patch v1] KVM: x86: Initializing all kvm_lapic_irq fields Date: Wed, 11 Mar 2020 15:05:59 -0400 [thread overview] Message-ID: <1ee122a6-7c6a-f630-ea38-9f78960b76be@redhat.com> (raw) In-Reply-To: <c4370fce-1bc7-3a82-91a7-37fcd013bd77@redhat.com> [-- Attachment #1.1: Type: text/plain, Size: 2241 bytes --] On 3/11/20 2:49 PM, Paolo Bonzini wrote: > On 11/03/20 19:34, Nitesh Narayan Lal wrote: >> Previously all fields of structure kvm_lapic_irq were not initialized >> before it was passed to kvm_bitmap_or_dest_vcpus(). Which will cause >> an issue when any of those fields are used for processing a request. >> This patch initializes all the fields of kvm_lapic_irq based on the >> values which are passed through the ioapic redirect_entry object. > Can you explain better how the bug manifests itself? For example not initializing the irq.msi_redir_hint field, could lead to a situation where it carries garbage (non-zero) value. This will lead to misbehavior of kvm_apic_map_get_dest_lapic() when it invokes the kvm_lowest_prio_delivery(), that will return true because of non-zero msi_redir_hint field. To be on the safe side, I thought of initializing other struct fields as well. If the above explanation makes sense, I can include it in the patch subject and send a second version of this patch? > > Thanks, > > Paolo > >> Fixes: 7ee30bc132c6("KVM: x86: deliver KVM IOAPIC scan request to target vCPUs") >> Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com> >> --- >> arch/x86/kvm/ioapic.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c >> index 7668fed..3a8467d 100644 >> --- a/arch/x86/kvm/ioapic.c >> +++ b/arch/x86/kvm/ioapic.c >> @@ -378,12 +378,15 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) >> if (e->fields.delivery_mode == APIC_DM_FIXED) { >> struct kvm_lapic_irq irq; >> >> - irq.shorthand = APIC_DEST_NOSHORT; >> irq.vector = e->fields.vector; >> irq.delivery_mode = e->fields.delivery_mode << 8; >> - irq.dest_id = e->fields.dest_id; >> irq.dest_mode = >> kvm_lapic_irq_dest_mode(!!e->fields.dest_mode); >> + irq.level = 1; >> + irq.trig_mode = e->fields.trig_mode; >> + irq.shorthand = APIC_DEST_NOSHORT; >> + irq.dest_id = e->fields.dest_id; >> + irq.msi_redir_hint = false; >> bitmap_zero(&vcpu_bitmap, 16); >> kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq, >> &vcpu_bitmap); >> -- Nitesh [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 833 bytes --]
prev parent reply other threads:[~2020-03-11 19:06 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-03-11 18:34 [Patch v1] KVM: x86: Initializing all kvm_lapic_irq fields Nitesh Narayan Lal 2020-03-11 18:49 ` Paolo Bonzini 2020-03-11 19:05 ` Nitesh Narayan Lal [this message]
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