lkml.org 
[lkml]   [2016]   [Jul]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v3 12/14] KVM: x86: add a flag to disable KVM x2apic broadcast quirk
    Date
    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: Radim Krčmář <rkrcmar@redhat.com>
    ---
    v3: new

    Documentation/virtual/kvm/api.txt | 5 +++++
    arch/x86/include/asm/kvm_host.h | 1 +
    arch/x86/kvm/lapic.c | 40 +++++++++++++++++++++++++++++----------
    arch/x86/kvm/x86.c | 5 ++++-
    include/uapi/linux/kvm.h | 1 +
    5 files changed, 41 insertions(+), 11 deletions(-)

    diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
    index 10e2bf903e57..c2753ff4a499 100644
    --- a/Documentation/virtual/kvm/api.txt
    +++ b/Documentation/virtual/kvm/api.txt
    @@ -3843,12 +3843,17 @@ Returns: 0 on success, -EINVAL when args[0] contains invalid features
    Valid feature flags in args[0] are

    #define KVM_X2APIC_API_USE_32BIT_FORMAT (1ULL << 0)
    +#define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1)

    Enabling KVM_X2APIC_API_USE_32BIT_FORMAT 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. A KVM quirk treats 0xff as a
    +broadcast even in x2APIC mode (a consequence of allowing physical x2APIC
    +without interrupt remapping).


    8. Other capabilities.
    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index f13522f85a1d..25bf9d627c15 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -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 {
    diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
    index d27a7829a4ce..46f1d1c93420 100644
    --- a/arch/x86/kvm/lapic.c
    +++ b/arch/x86/kvm/lapic.c
    @@ -619,14 +619,17 @@ 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 broadcast quirk can be disabled with KVM_CAP_X2APIC_API.
    */
    -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 +639,7 @@ 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 +691,28 @@ static void kvm_apic_disabled_lapic_found(struct kvm *kvm)
    }
    }

    +static bool kvm_apic_map_need_slowpath(struct kvm *kvm, struct kvm_lapic **src,
    + struct kvm_lapic_irq *irq, struct kvm_apic_map *map)
    +{
    + if (!map)
    + return true;
    +
    + 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 +726,6 @@ 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 +734,7 @@ 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 (kvm_apic_map_need_slowpath(kvm, src, irq, map))
    return false;

    if (irq->dest_mode == APIC_DEST_PHYSICAL) {
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 330276315daa..4bab85f82a96 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -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_FORMAT)
    +#define KVM_X2APIC_API_VALID_FLAGS (KVM_X2APIC_API_USE_32BIT_FORMAT | \
    + 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_FORMAT)
    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;
    diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
    index b6de3febabaa..13b30dfd93b2 100644
    --- a/include/uapi/linux/kvm.h
    +++ b/include/uapi/linux/kvm.h
    @@ -1315,5 +1315,6 @@ struct kvm_assigned_msix_entry {
    };

    #define KVM_X2APIC_API_USE_32BIT_FORMAT (1ULL << 0)
    +#define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1)

    #endif /* __LINUX_KVM_H */
    --
    2.9.0
    \
     
     \ /
      Last update: 2016-07-12 22:21    [W:2.845 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site