On 13/05/2015 03:47, Steve Rutherford wrote:
> Adds KVM_EXIT_IOAPIC_EOI which passes the interrupt vector up to
> userspace.
>
> Uses a per VCPU exit bitmap to decide whether or not the IOAPIC needs
> to be informed (which is identical to the EOI_EXIT_BITMAP field used
> by modern x86 processors, but can also be used to elide kvm IOAPIC EOI
> exits on older processors).
>
> [Note: A prototype using ResampleFDs found that decoupling the EOI
> from the VCPU's thread made it possible for the VCPU to not see a
> recent EOI after reentering the guest. This does not match real
> hardware.]
Can you explain this better (and perhaps add a testcase to ioapic.c)?
Paolo
> Compile tested for Intel x86.
>
> Signed-off-by: Steve Rutherford <srutherford@xxxxxxxxxx>
> ---
> Documentation/virtual/kvm/api.txt | 10 ++++++++++
> arch/x86/include/asm/kvm_host.h | 3 +++
> arch/x86/kvm/lapic.c | 9 +++++++++
> arch/x86/kvm/x86.c | 11 +++++++++++
> include/linux/kvm_host.h | 1 +
> include/uapi/linux/kvm.h | 5 +++++
> 6 files changed, 39 insertions(+)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 0744b4e..dd92996 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3285,6 +3285,16 @@ Valid values for 'type' are:
> */
> __u64 kvm_valid_regs;
> __u64 kvm_dirty_regs;
> +
> + /* KVM_EXIT_IOAPIC_EOI */
> + struct {
> + __u8 vector;
> + } eoi;
> +
> +Indicates that an eoi of a level triggered IOAPIC interrupt on vector has
> +occurred, which should be handled by the userspace IOAPIC. Triggers when
> +the Irqchip has been split between userspace and the kernel.
> +
> union {
> struct kvm_sync_regs regs;
> char padding[1024];
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 3ddc134..b1978f1 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -539,6 +539,9 @@ struct kvm_vcpu_arch {
> struct {
> bool pv_unhalted;
> } pv;
> +
> + u64 eoi_exit_bitmaps[4];
> + int pending_ioapic_eoi;
> };
>
> struct kvm_lpage_info {
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index bc392a6..42fada6f 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -860,6 +860,15 @@ int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2)
>
> static void kvm_ioapic_send_eoi(struct kvm_lapic *apic, int vector)
> {
> + if (irqchip_split(apic->vcpu->kvm)) {
> + if (test_bit(vector,
> + (void *) apic->vcpu->arch.eoi_exit_bitmaps)) {
> + apic->vcpu->arch.pending_ioapic_eoi = vector;
> + kvm_make_request(KVM_REQ_IOAPIC_EOI_EXIT, apic->vcpu);
> + }
> + return;
> + }
> +
> if (kvm_ioapic_handles_vector(apic->vcpu->kvm, vector)) {
> int trigger_mode;
> if (apic_test_vector(vector, apic->regs + APIC_TMR))
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 7505b39..cc27c35 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6324,6 +6324,17 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> kvm_handle_pmu_event(vcpu);
> if (kvm_check_request(KVM_REQ_PMI, vcpu))
> kvm_deliver_pmi(vcpu);
> + if (kvm_check_request(KVM_REQ_IOAPIC_EOI_EXIT, vcpu)) {
> + BUG_ON(vcpu->arch.pending_ioapic_eoi > 255);
> + if (test_bit(vcpu->arch.pending_ioapic_eoi,
> + (void *) vcpu->arch.eoi_exit_bitmaps)) {
> + vcpu->run->exit_reason = KVM_EXIT_IOAPIC_EOI;
> + vcpu->run->eoi.vector =
> + vcpu->arch.pending_ioapic_eoi;
> + r = 0;
> + goto out;
> + }
> + }
> if (kvm_check_request(KVM_REQ_SCAN_IOAPIC, vcpu))
> vcpu_scan_ioapic(vcpu);
> if (kvm_check_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu))
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 277b7a1..cef20ad 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -134,6 +134,7 @@ static inline bool is_error_page(struct page *page)
> #define KVM_REQ_ENABLE_IBS 23
> #define KVM_REQ_DISABLE_IBS 24
> #define KVM_REQ_APIC_PAGE_RELOAD 25
> +#define KVM_REQ_IOAPIC_EOI_EXIT 26
>
> #define KVM_USERSPACE_IRQ_SOURCE_ID 0
> #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 7d06dc4..2305948 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -183,6 +183,7 @@ struct kvm_s390_skeys {
> #define KVM_EXIT_EPR 23
> #define KVM_EXIT_SYSTEM_EVENT 24
> #define KVM_EXIT_S390_STSI 25
> +#define KVM_EXIT_IOAPIC_EOI 26
>
> /* For KVM_EXIT_INTERNAL_ERROR */
> /* Emulate instruction failed. */
> @@ -329,6 +330,10 @@ struct kvm_run {
> __u8 sel1;
> __u16 sel2;
> } s390_stsi;
> + /* KVM_EXIT_IOAPIC_EOI */
> + struct {
> + __u8 vector;
> + } eoi;
> /* Fix the size of the union. */
> char padding[256];
> };
>
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