KVM: x86: add a flag to disable KVM x2apic broadcast quirk (c519265f) · Commits · 戴 / test

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 @@ split_irqchip_unlock:

		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 */

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