Re: [PATCH v3 3/5] KVM: X86: Use APIC_DEST_* macros properly in kvm_lapic_irq.dest_mode

Vitaly Kuznetsov
2019-12-03T13:16:11Z

Peter Xu <peterx@redhat.com> writes:

> We were using either APIC_DEST_PHYSICAL|APIC_DEST_LOGICAL or 0|1 to
> fill in kvm_lapic_irq.dest_mode. It's fine 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. We'll have problem
> when we want to start checking against APIC_DEST_PHYSICAL

APIC_DEST_LOGICAL

> which does not equals to 1.
>
> This patch firstly introduces kvm_lapic_irq_dest_mode() helper to take
> any boolean of destination mode and return the APIC_DEST_* macro.
> Then, it replaces the 0|1 settings of irq.dest_mode with the helper.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> arch/x86/include/asm/kvm_host.h | 5 +++++
> arch/x86/kvm/ioapic.c | 8 +++++---
> arch/x86/kvm/irq_comm.c | 7 ++++---
> arch/x86/kvm/x86.c | 2 +-
> 4 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index b79cd6aa4075..f815c97b1b57 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1022,6 +1022,11 @@ struct kvm_lapic_irq {
> bool msi_redir_hint;
> };
>
> +static inline u16 kvm_lapic_irq_dest_mode(bool dest_mode)
> +{
> + return dest_mode ? APIC_DEST_LOGICAL : APIC_DEST_PHYSICAL;
> +}
> +
> struct kvm_x86_ops {
> int (*cpu_has_kvm_support)(void); /* __init */
> int (*disabled_by_bios)(void); /* __init */
> diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
> index 9fd2dd89a1c5..901d85237d1c 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 =
> + kvm_lapic_irq_dest_mode(e->fields.dest_mode);
> 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 =
> + kvm_lapic_irq_dest_mode(e->fields.dest_mode);
> kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq,
> &vcpu_bitmap);
> }
> @@ -369,7 +371,7 @@ 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 = kvm_lapic_irq_dest_mode(entry->fields.dest_mode);
> 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..5f59e5ebdbed 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 = kvm_lapic_irq_dest_mode(
> + (1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo);

This usage is a bit fishy (I understand that it works, but),
kvm_lapic_irq_dest_mode()'s input is bool (0/1) but here we're passing
something different.

I'm not sure kvm_lapic_irq_dest_mode() is even needed here, but in case
it is I'd suggest to add '!!':

kvm_lapic_irq_dest_mode(!!((1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo))

to make things explicit. I don't like how it looks though.

> 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;

--
Vitaly