Commit 35366901 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86: Explicitly track all possibilities for APIC map's logical modes 



Track all possibilities for the optimized APIC map's logical modes
instead of overloading the pseudo-bitmap and treating any "unknown" value
as "invalid".

As documented by the now-stale comment above the mode values, the values
did have meaning when the optimized map was originally added.  That
dependent logical was removed by commit e45115b6 ("KVM: x86: use
physical LAPIC array for logical x2APIC"), but the obfuscated behavior
and its comment were left behind.

Opportunistically rename "mode" to "logical_mode", partly to make it
clear that the "disabled" case applies only to the logical map, but also
to prove that there is no lurking code that expects "mode" to be a bitmap.

Functionally, this is a glorified nop.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20230106011306.85230-19-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 6ea567ca

arch/x86/include/asm/kvm_host.h

+20 −9
Original line number Diff line number Diff line
@@ -1022,19 +1022,30 @@ struct kvm_arch_memory_slot { 
};



/*

 * We use as the mode the number of bits allocated in the LDR for the

 * logical processor ID.  It happens that these are all powers of two.

 * This makes it is very easy to detect cases where the APICs are

 * configured for multiple modes; in that case, we cannot use the map and

 * hence cannot use kvm_irq_delivery_to_apic_fast either.

 * Track the mode of the optimized logical map, as the rules for decoding the

 * destination vary per mode.  Enabling the optimized logical map requires all

 * software-enabled local APIs to be in the same mode, each addressable APIC to

 * be mapped to only one MDA, and each MDA to map to at most one APIC.

 */

#define KVM_APIC_MODE_XAPIC_CLUSTER          4

#define KVM_APIC_MODE_XAPIC_FLAT             8

#define KVM_APIC_MODE_X2APIC                16

enum kvm_apic_logical_mode {

	/* All local APICs are software disabled. */

	KVM_APIC_MODE_SW_DISABLED,

	/* All software enabled local APICs in xAPIC cluster addressing mode. */

	KVM_APIC_MODE_XAPIC_CLUSTER,

	/* All software enabled local APICs in xAPIC flat addressing mode. */

	KVM_APIC_MODE_XAPIC_FLAT,

	/* All software enabled local APICs in x2APIC mode. */

	KVM_APIC_MODE_X2APIC,

	/*

	 * Optimized map disabled, e.g. not all local APICs in the same logical

	 * mode, same logical ID assigned to multiple APICs, etc.

	 */

	KVM_APIC_MODE_MAP_DISABLED,

};



struct kvm_apic_map {

	struct rcu_head rcu;

	u8 mode;

	enum kvm_apic_logical_mode logical_mode;

	u32 max_apic_id;

	union {

		struct kvm_lapic *xapic_flat_map[8];

arch/x86/kvm/lapic.c

+32 −8
Original line number Diff line number Diff line
@@ -168,7 +168,12 @@ static bool kvm_use_posted_timer_interrupt(struct kvm_vcpu *vcpu) 


static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map,

		u32 dest_id, struct kvm_lapic ***cluster, u16 *mask) {

	switch (map->mode) {

	switch (map->logical_mode) {

	case KVM_APIC_MODE_SW_DISABLED:

		/* Arbitrarily use the flat map so that @cluster isn't NULL. */

		*cluster = map->xapic_flat_map;

		*mask = 0;

		return true;

	case KVM_APIC_MODE_X2APIC: {

		u32 offset = (dest_id >> 16) * 16;

		u32 max_apic_id = map->max_apic_id;
@@ -193,8 +198,10 @@ static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map, 
		*cluster = map->xapic_cluster_map[(dest_id >> 4) & 0xf];

		*mask = dest_id & 0xf;

		return true;

	case KVM_APIC_MODE_MAP_DISABLED:

		return false;

	default:

		/* Not optimized. */

		WARN_ON_ONCE(1);

		return false;

	}

}
@@ -256,10 +263,12 @@ void kvm_recalculate_apic_map(struct kvm *kvm) 
		goto out;



	new->max_apic_id = max_id;

	new->logical_mode = KVM_APIC_MODE_SW_DISABLED;



	kvm_for_each_vcpu(i, vcpu, kvm) {

		struct kvm_lapic *apic = vcpu->arch.apic;

		struct kvm_lapic **cluster;

		enum kvm_apic_logical_mode logical_mode;

		u16 mask;

		u32 ldr;

		u8 xapic_id;
@@ -282,7 +291,8 @@ void kvm_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))

		if (new->logical_mode == KVM_APIC_MODE_MAP_DISABLED ||

		    !kvm_apic_sw_enabled(apic))

			continue;



		ldr = kvm_lapic_get_reg(apic, APIC_LDR);
@@ -290,17 +300,31 @@ void kvm_recalculate_apic_map(struct kvm *kvm) 
			continue;



		if (apic_x2apic_mode(apic)) {

			new->mode |= KVM_APIC_MODE_X2APIC;

			logical_mode = KVM_APIC_MODE_X2APIC;

		} else {

			ldr = GET_APIC_LOGICAL_ID(ldr);

			if (kvm_lapic_get_reg(apic, APIC_DFR) == APIC_DFR_FLAT)

				new->mode |= KVM_APIC_MODE_XAPIC_FLAT;

				logical_mode = KVM_APIC_MODE_XAPIC_FLAT;

			else

				new->mode |= KVM_APIC_MODE_XAPIC_CLUSTER;

				logical_mode = KVM_APIC_MODE_XAPIC_CLUSTER;

		}



		if (!kvm_apic_map_get_logical_dest(new, ldr, &cluster, &mask))

		/*

		 * To optimize logical mode delivery, all software-enabled APICs must

		 * be configured for the same mode.

		 */

		if (new->logical_mode == KVM_APIC_MODE_SW_DISABLED) {

			new->logical_mode = logical_mode;

		} else if (new->logical_mode != logical_mode) {

			new->logical_mode = KVM_APIC_MODE_MAP_DISABLED;

			continue;

		}



		if (WARN_ON_ONCE(!kvm_apic_map_get_logical_dest(new, ldr,

								&cluster, &mask))) {

			new->logical_mode = KVM_APIC_MODE_MAP_DISABLED;

			continue;

		}



		if (mask)

			cluster[ffs(mask) - 1] = apic;
@@ -953,7 +977,7 @@ static bool kvm_apic_is_broadcast_dest(struct kvm *kvm, struct kvm_lapic **src, 
{

	if (kvm->arch.x2apic_broadcast_quirk_disabled) {

		if ((irq->dest_id == APIC_BROADCAST &&

				map->mode != KVM_APIC_MODE_X2APIC))

		     map->logical_mode != KVM_APIC_MODE_X2APIC))

			return true;

		if (irq->dest_id == X2APIC_BROADCAST)

			return true;