On 6/28/2025 12:25 AM, Manali Shukla wrote: > Modern AMD processors expose four additional extended LVT registers in > the extended APIC register space, which can be used for additional > interrupt sources such as instruction-based sampling and others. > > To support this, introduce two new vCPU-based IOCTLs: > KVM_GET_LAPIC_W_EXTAPIC and KVM_SET_LAPIC_W_EXTAPIC. These IOCTLs works > similarly to KVM_GET_LAPIC and KVM_SET_LAPIC, but operate on APIC page > with extended APIC register space located at APIC offsets 400h-530h. > > These IOCTLs are intended for use when extended APIC support is > enabled in the guest. They allow saving and restoring the full APIC > page, including the extended registers. > > To support this, the `struct kvm_lapic_state_w_extapic` has been made > extensible rather than hardcoding its size, improving forward > compatibility. > > Documentation for the new IOCTLs has also been added. > > For more details on the extended APIC space, refer to AMD Programmer’s > Manual Volume 2, Section 16.4.5: Extended Interrupts. > https://bugzilla.kernel.org/attachment.cgi?id=306250 > > Signed-off-by: Manali Shukla <manali.shukla@xxxxxxx> > --- > Documentation/virt/kvm/api.rst | 23 ++++++++++++++++++++ > arch/x86/include/uapi/asm/kvm.h | 5 +++++ > arch/x86/kvm/lapic.c | 12 ++++++----- > arch/x86/kvm/lapic.h | 6 ++++-- > arch/x86/kvm/x86.c | 37 ++++++++++++++++++++++++--------- > include/uapi/linux/kvm.h | 10 +++++++++ > 6 files changed, 76 insertions(+), 17 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 1bd2d42e6424..0ca11d43f833 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -2041,6 +2041,18 @@ error. > Reads the Local APIC registers and copies them into the input argument. The > data format and layout are the same as documented in the architecture manual. > > +:: > + > + #define KVM_APIC_EXT_REG_SIZE 0x540 > + struct kvm_lapic_state_w_extapic { > + __DECLARE_FLEX_ARRAY(__u8, regs); > + }; > + > +Applications should use KVM_GET_LAPIC_W_EXTAPIC ioctl if extended APIC is > +enabled. KVM_GET_LAPIC_W_EXTAPIC reads Local APIC registers with extended > +APIC register space located at offsets 400h-530h and copies them into input > +argument. > + > If KVM_X2APIC_API_USE_32BIT_IDS feature of KVM_CAP_X2APIC_API is > enabled, then the format of APIC_ID register depends on the APIC mode > (reported by MSR_IA32_APICBASE) of its VCPU. x2APIC stores APIC ID in > @@ -2072,6 +2084,17 @@ always uses xAPIC format. > Copies the input argument into the Local APIC registers. The data format > and layout are the same as documented in the architecture manual. > > +:: > + > + #define KVM_APIC_EXT_REG_SIZE 0x540 > + struct kvm_lapic_state_w_extapic { > + __DECLARE_FLEX_ARRAY(__u8, regs); > + }; > + > +Applications should use KVM_SET_LAPIC_W_EXTAPIC ioctl if extended APIC is enabled. > +KVM_SET_LAPIC_W_EXTAPIC copies input arguments with extended APIC register into > +Local APIC and extended APIC registers. > + > The format of the APIC ID register (bytes 32-35 of struct kvm_lapic_state's > regs field) depends on the state of the KVM_CAP_X2APIC_API capability. > See the note in KVM_GET_LAPIC. > diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h > index 6f3499507c5e..91c3c5b8cae3 100644 > --- a/arch/x86/include/uapi/asm/kvm.h > +++ b/arch/x86/include/uapi/asm/kvm.h > @@ -124,6 +124,11 @@ struct kvm_lapic_state { > char regs[KVM_APIC_REG_SIZE]; > }; > > +#define KVM_APIC_EXT_REG_SIZE 0x540 > +struct kvm_lapic_state_w_extapic { > + __DECLARE_FLEX_ARRAY(__u8, regs); > +}; The name "kvm_lapic_state_w_extapic" seems a little bit too long, maybe "kvm_ext_lapic_state" is enough? > + > struct kvm_segment { > __u64 base; > __u32 limit; > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 73418dc0ebb2..00ca2b0faa45 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -3046,7 +3046,7 @@ void kvm_apic_ack_interrupt(struct kvm_vcpu *vcpu, int vector) > EXPORT_SYMBOL_GPL(kvm_apic_ack_interrupt); > > static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu, > - struct kvm_lapic_state *s, bool set) > + struct kvm_lapic_state_w_extapic *s, bool set) > { > if (apic_x2apic_mode(vcpu->arch.apic)) { > u32 x2apic_id = kvm_x2apic_id(vcpu->arch.apic); > @@ -3097,9 +3097,10 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu, > return 0; > } > > -int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s) > +int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state_w_extapic *s, > + unsigned int size) > { > - memcpy(s->regs, vcpu->arch.apic->regs, sizeof(*s)); > + memcpy(s->regs, vcpu->arch.apic->regs, size); > > /* > * Get calculated timer current count for remaining timer period (if > @@ -3111,7 +3112,8 @@ int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s) > return kvm_apic_state_fixup(vcpu, s, false); > } > > -int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s) > +int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state_w_extapic *s, > + unsigned int size) > { > struct kvm_lapic *apic = vcpu->arch.apic; > int r; > @@ -3126,7 +3128,7 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s) > kvm_recalculate_apic_map(vcpu->kvm); > return r; > } > - memcpy(vcpu->arch.apic->regs, s->regs, sizeof(*s)); > + memcpy(vcpu->arch.apic->regs, s->regs, size); > > atomic_set_release(&apic->vcpu->kvm->arch.apic_map_dirty, DIRTY); > kvm_recalculate_apic_map(vcpu->kvm); > diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h > index 4518b4e0552f..7ad946b3738d 100644 > --- a/arch/x86/kvm/lapic.h > +++ b/arch/x86/kvm/lapic.h > @@ -120,9 +120,11 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src, > void kvm_apic_send_ipi(struct kvm_lapic *apic, u32 icr_low, u32 icr_high); > > int kvm_apic_set_base(struct kvm_vcpu *vcpu, u64 value, bool host_initiated); > -int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s); > -int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s); > void kvm_apic_update_hwapic_isr(struct kvm_vcpu *vcpu); > +int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state_w_extapic *s, > + unsigned int size); > +int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state_w_extapic *s, > + unsigned int size); > int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu); > > u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu); > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index c880a512005e..c273bbbbbcc6 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5156,25 +5156,25 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) > } > > static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu, > - struct kvm_lapic_state *s) > + struct kvm_lapic_state_w_extapic *s, unsigned int size) > { > if (vcpu->arch.apic->guest_apic_protected) > return -EINVAL; > > kvm_x86_call(sync_pir_to_irr)(vcpu); > > - return kvm_apic_get_state(vcpu, s); > + return kvm_apic_get_state(vcpu, s, size); > } > > static int kvm_vcpu_ioctl_set_lapic(struct kvm_vcpu *vcpu, > - struct kvm_lapic_state *s) > + struct kvm_lapic_state_w_extapic *s, unsigned int size) > { > int r; > > if (vcpu->arch.apic->guest_apic_protected) > return -EINVAL; > > - r = kvm_apic_set_state(vcpu, s); > + r = kvm_apic_set_state(vcpu, s, size); > if (r) > return r; > update_cr8_intercept(vcpu); > @@ -5903,10 +5903,11 @@ long kvm_arch_vcpu_ioctl(struct file *filp, > { > struct kvm_vcpu *vcpu = filp->private_data; > void __user *argp = (void __user *)arg; > + unsigned long size; > int r; > union { > struct kvm_sregs2 *sregs2; > - struct kvm_lapic_state *lapic; > + struct kvm_lapic_state_w_extapic *lapic; > struct kvm_xsave *xsave; > struct kvm_xcrs *xcrs; > void *buffer; > @@ -5916,35 +5917,51 @@ long kvm_arch_vcpu_ioctl(struct file *filp, > > u.buffer = NULL; > switch (ioctl) { > + case KVM_GET_LAPIC_W_EXTAPIC: > case KVM_GET_LAPIC: { > r = -EINVAL; > if (!lapic_in_kernel(vcpu)) > goto out; > - u.lapic = kzalloc(sizeof(struct kvm_lapic_state), GFP_KERNEL); > + > + if (ioctl == KVM_GET_LAPIC_W_EXTAPIC) > + size = struct_size(u.lapic, regs, KVM_APIC_EXT_REG_SIZE); > + else > + size = sizeof(struct kvm_lapic_state); > + > + u.lapic = kzalloc(size, GFP_KERNEL); > > r = -ENOMEM; > if (!u.lapic) > goto out; > - r = kvm_vcpu_ioctl_get_lapic(vcpu, u.lapic); > + r = kvm_vcpu_ioctl_get_lapic(vcpu, u.lapic, size); > if (r) > goto out; > + > r = -EFAULT; > - if (copy_to_user(argp, u.lapic, sizeof(struct kvm_lapic_state))) > + if (copy_to_user(argp, u.lapic, size)) > goto out; > + > r = 0; > break; > } > + case KVM_SET_LAPIC_W_EXTAPIC: > case KVM_SET_LAPIC: { > r = -EINVAL; > if (!lapic_in_kernel(vcpu)) > goto out; > - u.lapic = memdup_user(argp, sizeof(*u.lapic)); > + > + if (ioctl == KVM_SET_LAPIC_W_EXTAPIC) > + size = struct_size(u.lapic, regs, KVM_APIC_EXT_REG_SIZE); > + else > + size = sizeof(struct kvm_lapic_state); > + u.lapic = memdup_user(argp, size); > + > if (IS_ERR(u.lapic)) { > r = PTR_ERR(u.lapic); > goto out_nofree; > } > > - r = kvm_vcpu_ioctl_set_lapic(vcpu, u.lapic); > + r = kvm_vcpu_ioctl_set_lapic(vcpu, u.lapic, size); > break; > } > case KVM_INTERRUPT: { > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index d00b85cb168c..cf23c1b52c49 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -1290,6 +1290,16 @@ struct kvm_vfio_spapr_tce { > #define KVM_SET_FPU _IOW(KVMIO, 0x8d, struct kvm_fpu) > #define KVM_GET_LAPIC _IOR(KVMIO, 0x8e, struct kvm_lapic_state) > #define KVM_SET_LAPIC _IOW(KVMIO, 0x8f, struct kvm_lapic_state) > +/* > + * Added to save/restore local APIC registers with extended APIC (extapic) > + * register space. > + * > + * Qemu emulates extapic logic only when KVM enables extapic functionality via > + * KVM capability. In the condition where Qemu sets extapic registers, but KVM doesn't > + * set extapic capability, Qemu ends up using KVM_GET_LAPIC and KVM_SET_LAPIC. > + */ > +#define KVM_GET_LAPIC_W_EXTAPIC _IOR(KVMIO, 0x8e, struct kvm_lapic_state_w_extapic) > +#define KVM_SET_LAPIC_W_EXTAPIC _IOW(KVMIO, 0x8f, struct kvm_lapic_state_w_extapic) > #define KVM_SET_CPUID2 _IOW(KVMIO, 0x90, struct kvm_cpuid2) > #define KVM_GET_CPUID2 _IOWR(KVMIO, 0x91, struct kvm_cpuid2) > /* Available with KVM_CAP_VAPIC */
