linux-kernel - Re: [PATCH] KVM: X86: Use APIC_DEST

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Date:   Fri, 29 Nov 2019 11:17:31 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Nitesh Narayan Lal <nitesh@...hat.com>
Subject: Re: [PATCH] KVM: X86: Use APIC_DEST_* macros properly

On Fri, Nov 29, 2019 at 03:23:36PM +0100, Vitaly Kuznetsov wrote:
> Peter Xu <peterx@...hat.com> writes:
> 
> > Previously we were using either APIC_DEST_PHYSICAL|APIC_DEST_LOGICAL
> > or 0|1 to fill in kvm_lapic_irq.dest_mode, and it's done in an adhoc
> > way.  It's fine imho only because in most cases when we check against
> > dest_mode it's against APIC_DEST_PHYSICAL (which equals to 0).
> > However, that's not consistent, majorly because APIC_DEST_LOGICAL does
> > not equals to 1, so if one day we check irq.dest_mode against
> > APIC_DEST_LOGICAL we'll probably always get a false returned.
> >
> > This patch replaces the 0/1 settings of irq.dest_mode with the macros
> > to make them consistent.
> >
> > CC: Paolo Bonzini <pbonzini@...hat.com>
> > CC: Sean Christopherson <sean.j.christopherson@...el.com>
> > CC: Vitaly Kuznetsov <vkuznets@...hat.com>
> > CC: Nitesh Narayan Lal <nitesh@...hat.com>
> > Signed-off-by: Peter Xu <peterx@...hat.com>
> > ---
> >  arch/x86/kvm/ioapic.c   | 9 ++++++---
> >  arch/x86/kvm/irq_comm.c | 7 ++++---
> >  arch/x86/kvm/x86.c      | 2 +-
> >  3 files changed, 11 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
> > index 9fd2dd89a1c5..1e091637d5d5 100644
> > --- a/arch/x86/kvm/ioapic.c
> > +++ b/arch/x86/kvm/ioapic.c
> > @@ -331,7 +331,8 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
> >  			irq.vector = e->fields.vector;
> >  			irq.delivery_mode = e->fields.delivery_mode << 8;
> >  			irq.dest_id = e->fields.dest_id;
> > -			irq.dest_mode = e->fields.dest_mode;
> > +			irq.dest_mode = e->fields.dest_mode ?
> > +			    APIC_DEST_LOGICAL : APIC_DEST_PHYSICAL;
> >  			bitmap_zero(&vcpu_bitmap, 16);
> >  			kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq,
> >  						 &vcpu_bitmap);
> > @@ -343,7 +344,8 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
> >  				 * keep ioapic_handled_vectors synchronized.
> >  				 */
> >  				irq.dest_id = old_dest_id;
> > -				irq.dest_mode = old_dest_mode;
> > +				irq.dest_mode = old_dest_mode ?
> > +				    APIC_DEST_LOGICAL : APIC_DEST_PHYSICAL;
> >  				kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq,
> >  							 &vcpu_bitmap);
> >  			}
> > @@ -369,7 +371,8 @@ static int ioapic_service(struct kvm_ioapic *ioapic, int irq, bool line_status)
> >  
> >  	irqe.dest_id = entry->fields.dest_id;
> >  	irqe.vector = entry->fields.vector;
> > -	irqe.dest_mode = entry->fields.dest_mode;
> > +	irqe.dest_mode = entry->fields.dest_mode ?
> > +	    APIC_DEST_LOGICAL : APIC_DEST_PHYSICAL;
> >  	irqe.trig_mode = entry->fields.trig_mode;
> >  	irqe.delivery_mode = entry->fields.delivery_mode << 8;
> >  	irqe.level = 1;
> > diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
> > index 8ecd48d31800..673b6afd6dbf 100644
> > --- a/arch/x86/kvm/irq_comm.c
> > +++ b/arch/x86/kvm/irq_comm.c
> > @@ -52,8 +52,8 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> >  	unsigned long dest_vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)];
> >  	unsigned int dest_vcpus = 0;
> >  
> > -	if (irq->dest_mode == 0 && irq->dest_id == 0xff &&
> > -			kvm_lowest_prio_delivery(irq)) {
> > +	if (irq->dest_mode == APIC_DEST_PHYSICAL &&
> > +	    irq->dest_id == 0xff && kvm_lowest_prio_delivery(irq)) {
> >  		printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n");
> >  		irq->delivery_mode = APIC_DM_FIXED;
> >  	}
> > @@ -114,7 +114,8 @@ void kvm_set_msi_irq(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e,
> >  		irq->dest_id |= MSI_ADDR_EXT_DEST_ID(e->msi.address_hi);
> >  	irq->vector = (e->msi.data &
> >  			MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT;
> > -	irq->dest_mode = (1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo;
> > +	irq->dest_mode = (1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo ?
> > +	    APIC_DEST_LOGICAL : APIC_DEST_PHYSICAL;
> >  	irq->trig_mode = (1 << MSI_DATA_TRIGGER_SHIFT) & e->msi.data;
> >  	irq->delivery_mode = e->msi.data & 0x700;
> >  	irq->msi_redir_hint = ((e->msi.address_lo
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 3ed167e039e5..3b00d662dc14 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -7356,7 +7356,7 @@ static void kvm_pv_kick_cpu_op(struct kvm *kvm, unsigned long flags, int apicid)
> >  	struct kvm_lapic_irq lapic_irq;
> >  
> >  	lapic_irq.shorthand = 0;
> > -	lapic_irq.dest_mode = 0;
> > +	lapic_irq.dest_mode = APIC_DEST_PHYSICAL;
> >  	lapic_irq.level = 0;
> >  	lapic_irq.dest_id = apicid;
> >  	lapic_irq.msi_redir_hint = false;
> 
> dest_mode is being passed to kvm_apic_match_dest() where we do:
> 
> 	case APIC_DEST_NOSHORT:
> 		if (dest_mode == APIC_DEST_PHYSICAL)
> 			return kvm_apic_match_physical_addr(target, mda);
> 		else
> 			return kvm_apic_match_logical_addr(target, mda);
> 
> I'd suggest we fix this too then (and BUG() in case it's neither).

That's true.  Let me add another patch to fix it (probably easier by
changing the type of dest_mode param in kvm_apic_match_dest from int
to bool).

Thanks,

-- 
Peter Xu