lkml.org 
[lkml]   [2023]   [Nov]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    SubjectRe: [RFC 09/33] KVM: x86: hyper-v: Introduce per-VTL vcpu helpers
    From
    Date
    On Wed, 2023-11-08 at 11:17 +0000, Nicolas Saenz Julienne wrote:
    > Introduce two helper functions. The first one queries a vCPU's VTL
    > level, the second one, given a struct kvm_vcpu and VTL pair, returns the
    > corresponding 'sibling' struct kvm_vcpu at the right VTL.
    >
    > We keep track of each VTL's state by having a distinct struct kvm_vpcu
    > for each level. VTL-vCPUs that belong to the same guest CPU share the
    > same physical APIC id, but belong to different APIC groups where the
    > apic group represents the vCPU's VTL.
    >
    > Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
    > ---
    > arch/x86/kvm/hyperv.h | 18 ++++++++++++++++++
    > 1 file changed, 18 insertions(+)
    >
    > diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
    > index 2bfed69ba0db..5433107e7cc8 100644
    > --- a/arch/x86/kvm/hyperv.h
    > +++ b/arch/x86/kvm/hyperv.h
    > @@ -23,6 +23,7 @@
    >
    > #include <linux/kvm_host.h>
    > #include "x86.h"
    > +#include "lapic.h"
    >
    > /* "Hv#1" signature */
    > #define HYPERV_CPUID_SIGNATURE_EAX 0x31237648
    > @@ -83,6 +84,23 @@ static inline struct kvm_hv_syndbg *to_hv_syndbg(struct kvm_vcpu *vcpu)
    > return &vcpu->kvm->arch.hyperv.hv_syndbg;
    > }
    >
    > +static inline struct kvm_vcpu *kvm_hv_get_vtl_vcpu(struct kvm_vcpu *vcpu, int vtl)
    > +{
    > + struct kvm *kvm = vcpu->kvm;
    > + u32 target_id = kvm_apic_id(vcpu);
    > +
    > + kvm_apic_id_set_group(kvm, vtl, &target_id);
    > + if (vcpu->vcpu_id == target_id)
    > + return vcpu;
    > +
    > + return kvm_get_vcpu_by_id(kvm, target_id);
    > +}

    > +
    > +static inline u8 kvm_hv_get_active_vtl(struct kvm_vcpu *vcpu)
    > +{
    > + return kvm_apic_group(vcpu);
    > +}
    > +
    > static inline u32 kvm_hv_get_vpindex(struct kvm_vcpu *vcpu)
    > {
    > struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);


    Ideally I'll prefer the kernel to not know the VTL mapping at all but rather,
    that each vCPU be assigned to an apic group / namespace and has its assigned VTL.

    Then the kernel works in this way:

    * Regular APIC IPI -> send it to the apic namespace to which the sender belongs or if we go with the idea of using
    multiple VMs, then this will work unmodified.
    * Hardware interrupt -> send it to the vCPU/VM which userspace configured it to send via GSI mappings.

    * HyperV IPI -> if same VTL as the vCPU assigned VTL -> deal with it the same as with regular IPI
    -> otherwise exit to the userspace.

    * Page fault -> if related to violation of current VTL protection,
    exit to userspace, and the userspace can then queue the SynIC message, and wakeup the higher VTL.


    Best regards,
    Maxim Levitsky



    \
     
     \ /
      Last update: 2023-11-28 08:25    [W:2.466 / U:0.048 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site