Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit c519265f authored by Radim Krčmář's avatar Radim Krčmář Committed by Paolo Bonzini
Browse files

KVM: x86: add a flag to disable KVM x2apic broadcast quirk 



Add KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK as a feature flag to
KVM_CAP_X2APIC_API.

The quirk made KVM interpret 0xff as a broadcast even in x2APIC mode.
The enableable capability is needed in order to support standard x2APIC and
remain backward compatible.

Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
[Expand kvm_apic_mda comment. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 37131313

Documentation/virtual/kvm/api.txt

+6 −0
Original line number Diff line number Diff line
@@ -3844,12 +3844,18 @@ Returns: 0 on success, -EINVAL when args[0] contains invalid features 
Valid feature flags in args[0] are



#define KVM_X2APIC_API_USE_32BIT_IDS            (1ULL << 0)

#define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK  (1ULL << 1)



Enabling KVM_X2APIC_API_USE_32BIT_IDS changes the behavior of

KVM_SET_GSI_ROUTING, KVM_SIGNAL_MSI, KVM_SET_LAPIC, and KVM_GET_LAPIC,

allowing the use of 32-bit APIC IDs.  See KVM_CAP_X2APIC_API in their

respective sections.



KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK must be enabled for x2APIC to work

in logical mode or with more than 255 VCPUs.  Otherwise, KVM treats 0xff

as a broadcast even in x2APIC mode in order to support physical x2APIC

without interrupt remapping.  This is undesirable in logical mode,

where 0xff represents CPUs 0-7 in cluster 0.





8. Other capabilities.

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -784,6 +784,7 @@ struct kvm_arch { 
	struct page *avic_physical_id_table_page;



	bool x2apic_format;

	bool x2apic_broadcast_quirk_disabled;

};



struct kvm_vm_stat {

arch/x86/kvm/lapic.c

+40 −13
Original line number Diff line number Diff line
@@ -616,17 +616,30 @@ static bool kvm_apic_match_logical_addr(struct kvm_lapic *apic, u32 mda) 
	}

}



/* KVM APIC implementation has two quirks

 *  - dest always begins at 0 while xAPIC MDA has offset 24,

 *  - IOxAPIC messages have to be delivered (directly) to x2APIC.

/* The KVM local APIC implementation has two quirks:

 *

 *  - the xAPIC MDA stores the destination at bits 24-31, while this

 *    is not true of struct kvm_lapic_irq's dest_id field.  This is

 *    just a quirk in the API and is not problematic.

 *

 *  - in-kernel IOAPIC messages have to be delivered directly to

 *    x2APIC, because the kernel does not support interrupt remapping.

 *    In order to support broadcast without interrupt remapping, x2APIC

 *    rewrites the destination of non-IPI messages from APIC_BROADCAST

 *    to X2APIC_BROADCAST.

 *

 * The broadcast quirk can be disabled with KVM_CAP_X2APIC_API.  This is

 * important when userspace wants to use x2APIC-format MSIs, because

 * APIC_BROADCAST (0xff) is a legal route for "cluster 0, CPUs 0-7".

 */

static u32 kvm_apic_mda(unsigned int dest_id, struct kvm_lapic *source,

                                              struct kvm_lapic *target)

static u32 kvm_apic_mda(struct kvm_vcpu *vcpu, unsigned int dest_id,

		struct kvm_lapic *source, struct kvm_lapic *target)

{

	bool ipi = source != NULL;

	bool x2apic_mda = apic_x2apic_mode(ipi ? source : target);



	if (!ipi && dest_id == APIC_BROADCAST && x2apic_mda)

	if (!vcpu->kvm->arch.x2apic_broadcast_quirk_disabled &&

	    !ipi && dest_id == APIC_BROADCAST && x2apic_mda)

		return X2APIC_BROADCAST;



	return x2apic_mda ? dest_id : SET_APIC_DEST_FIELD(dest_id);
@@ -636,7 +649,7 @@ bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source, 
			   int short_hand, unsigned int dest, int dest_mode)

{

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

	u32 mda = kvm_apic_mda(dest, source, target);

	u32 mda = kvm_apic_mda(vcpu, dest, source, target);



	apic_debug("target %p, source %p, dest 0x%x, "

		   "dest_mode 0x%x, short_hand 0x%x\n",
@@ -688,6 +701,25 @@ static void kvm_apic_disabled_lapic_found(struct kvm *kvm) 
	}

}



static bool kvm_apic_is_broadcast_dest(struct kvm *kvm, struct kvm_lapic **src,

		struct kvm_lapic_irq *irq, struct kvm_apic_map *map)

{

	if (kvm->arch.x2apic_broadcast_quirk_disabled) {

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

				map->mode != KVM_APIC_MODE_X2APIC))

			return true;

		if (irq->dest_id == X2APIC_BROADCAST)

			return true;

	} else {

		bool x2apic_ipi = src && *src && apic_x2apic_mode(*src);

		if (irq->dest_id == (x2apic_ipi ?

		                     X2APIC_BROADCAST : APIC_BROADCAST))

			return true;

	}



	return false;

}



/* Return true if the interrupt can be handled by using *bitmap as index mask

 * for valid destinations in *dst array.

 * Return false if kvm_apic_map_get_dest_lapic did nothing useful.
@@ -701,7 +733,6 @@ static inline bool kvm_apic_map_get_dest_lapic(struct kvm *kvm, 
		unsigned long *bitmap)

{

	int i, lowest;

	bool x2apic_ipi;



	if (irq->shorthand == APIC_DEST_SELF && src) {

		*dst = src;
@@ -710,11 +741,7 @@ static inline bool kvm_apic_map_get_dest_lapic(struct kvm *kvm, 
	} else if (irq->shorthand)

		return false;



	x2apic_ipi = src && *src && apic_x2apic_mode(*src);

	if (irq->dest_id == (x2apic_ipi ? X2APIC_BROADCAST : APIC_BROADCAST))

		return false;



	if (!map)

	if (!map || kvm_apic_is_broadcast_dest(kvm, src, irq, map))

		return false;



	if (irq->dest_mode == APIC_DEST_PHYSICAL) {

arch/x86/kvm/x86.c

+4 −1
Original line number Diff line number Diff line
@@ -90,7 +90,8 @@ static u64 __read_mostly efer_reserved_bits = ~((u64)EFER_SCE); 
#define VM_STAT(x) offsetof(struct kvm, stat.x), KVM_STAT_VM

#define VCPU_STAT(x) offsetof(struct kvm_vcpu, stat.x), KVM_STAT_VCPU



#define KVM_X2APIC_API_VALID_FLAGS (KVM_X2APIC_API_USE_32BIT_IDS)

#define KVM_X2APIC_API_VALID_FLAGS (KVM_X2APIC_API_USE_32BIT_IDS | \

                                    KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK)



static void update_cr8_intercept(struct kvm_vcpu *vcpu);

static void process_nmi(struct kvm_vcpu *vcpu);
@@ -3811,6 +3812,8 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, 


		if (cap->args[0] & KVM_X2APIC_API_USE_32BIT_IDS)

			kvm->arch.x2apic_format = true;

		if (cap->args[0] & KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK)

			kvm->arch.x2apic_broadcast_quirk_disabled = true;



		r = 0;

		break;

include/uapi/linux/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -1315,5 +1315,6 @@ struct kvm_assigned_msix_entry { 
};



#define KVM_X2APIC_API_USE_32BIT_IDS            (1ULL << 0)

#define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK  (1ULL << 1)



#endif /* __LINUX_KVM_H */