lkml.org 
[lkml]   [2020]   [Dec]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH v2 1/4] KVM: PPC: Allow nested guest creation when L0 hv_guest_state > L1
    Date
    Ravi Bangoria <ravi.bangoria@linux.ibm.com> writes:

    > On powerpc, L1 hypervisor takes help of L0 using H_ENTER_NESTED
    > hcall to load L2 guest state in cpu. L1 hypervisor prepares the
    > L2 state in struct hv_guest_state and passes a pointer to it via
    > hcall. Using that pointer, L0 reads/writes that state directly
    > from/to L1 memory. Thus L0 must be aware of hv_guest_state layout
    > of L1. Currently it uses version field to achieve this. i.e. If
    > L0 hv_guest_state.version != L1 hv_guest_state.version, L0 won't
    > allow nested kvm guest.
    >
    > This restriction can be loosen up a bit. L0 can be taught to
    > understand older layout of hv_guest_state, if we restrict the
    > new member to be added only at the end. i.e. we can allow
    > nested guest even when L0 hv_guest_state.version > L1
    > hv_guest_state.version. Though, the other way around is not
    > possible.
    >
    > Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>

    Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>

    > ---
    > arch/powerpc/include/asm/hvcall.h | 17 +++++++--
    > arch/powerpc/kvm/book3s_hv_nested.c | 53 ++++++++++++++++++++++++-----
    > 2 files changed, 59 insertions(+), 11 deletions(-)
    >
    > diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
    > index fbb377055471..a7073fddb657 100644
    > --- a/arch/powerpc/include/asm/hvcall.h
    > +++ b/arch/powerpc/include/asm/hvcall.h
    > @@ -524,9 +524,12 @@ struct h_cpu_char_result {
    > u64 behaviour;
    > };
    >
    > -/* Register state for entering a nested guest with H_ENTER_NESTED */
    > +/*
    > + * Register state for entering a nested guest with H_ENTER_NESTED.
    > + * New member must be added at the end.
    > + */
    > struct hv_guest_state {
    > - u64 version; /* version of this structure layout */
    > + u64 version; /* version of this structure layout, must be first */
    > u32 lpid;
    > u32 vcpu_token;
    > /* These registers are hypervisor privileged (at least for writing) */
    > @@ -560,6 +563,16 @@ struct hv_guest_state {
    > /* Latest version of hv_guest_state structure */
    > #define HV_GUEST_STATE_VERSION 1
    >
    > +static inline int hv_guest_state_size(unsigned int version)
    > +{
    > + switch (version) {
    > + case 1:
    > + return offsetofend(struct hv_guest_state, ppr);
    > + default:
    > + return -1;
    > + }
    > +}
    > +
    > #endif /* __ASSEMBLY__ */
    > #endif /* __KERNEL__ */
    > #endif /* _ASM_POWERPC_HVCALL_H */
    > diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
    > index 33b58549a9aa..2b433c3bacea 100644
    > --- a/arch/powerpc/kvm/book3s_hv_nested.c
    > +++ b/arch/powerpc/kvm/book3s_hv_nested.c
    > @@ -215,6 +215,45 @@ static void kvmhv_nested_mmio_needed(struct kvm_vcpu *vcpu, u64 regs_ptr)
    > }
    > }
    >
    > +static int kvmhv_read_guest_state_and_regs(struct kvm_vcpu *vcpu,
    > + struct hv_guest_state *l2_hv,
    > + struct pt_regs *l2_regs,
    > + u64 hv_ptr, u64 regs_ptr)
    > +{
    > + int size;
    > +
    > + if (kvm_vcpu_read_guest(vcpu, hv_ptr, &(l2_hv->version),
    > + sizeof(l2_hv->version)))
    > + return -1;
    > +
    > + if (kvmppc_need_byteswap(vcpu))
    > + l2_hv->version = swab64(l2_hv->version);
    > +
    > + size = hv_guest_state_size(l2_hv->version);
    > + if (size < 0)
    > + return -1;
    > +
    > + return kvm_vcpu_read_guest(vcpu, hv_ptr, l2_hv, size) ||
    > + kvm_vcpu_read_guest(vcpu, regs_ptr, l2_regs,
    > + sizeof(struct pt_regs));
    > +}
    > +
    > +static int kvmhv_write_guest_state_and_regs(struct kvm_vcpu *vcpu,
    > + struct hv_guest_state *l2_hv,
    > + struct pt_regs *l2_regs,
    > + u64 hv_ptr, u64 regs_ptr)
    > +{
    > + int size;
    > +
    > + size = hv_guest_state_size(l2_hv->version);
    > + if (size < 0)
    > + return -1;
    > +
    > + return kvm_vcpu_write_guest(vcpu, hv_ptr, l2_hv, size) ||
    > + kvm_vcpu_write_guest(vcpu, regs_ptr, l2_regs,
    > + sizeof(struct pt_regs));
    > +}
    > +
    > long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
    > {
    > long int err, r;
    > @@ -235,17 +274,15 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
    > hv_ptr = kvmppc_get_gpr(vcpu, 4);
    > regs_ptr = kvmppc_get_gpr(vcpu, 5);
    > vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
    > - err = kvm_vcpu_read_guest(vcpu, hv_ptr, &l2_hv,
    > - sizeof(struct hv_guest_state)) ||
    > - kvm_vcpu_read_guest(vcpu, regs_ptr, &l2_regs,
    > - sizeof(struct pt_regs));
    > + err = kvmhv_read_guest_state_and_regs(vcpu, &l2_hv, &l2_regs,
    > + hv_ptr, regs_ptr);
    > srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
    > if (err)
    > return H_PARAMETER;
    >
    > if (kvmppc_need_byteswap(vcpu))
    > byteswap_hv_regs(&l2_hv);
    > - if (l2_hv.version != HV_GUEST_STATE_VERSION)
    > + if (l2_hv.version > HV_GUEST_STATE_VERSION)
    > return H_P2;
    >
    > if (kvmppc_need_byteswap(vcpu))
    > @@ -325,10 +362,8 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
    > byteswap_pt_regs(&l2_regs);
    > }
    > vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
    > - err = kvm_vcpu_write_guest(vcpu, hv_ptr, &l2_hv,
    > - sizeof(struct hv_guest_state)) ||
    > - kvm_vcpu_write_guest(vcpu, regs_ptr, &l2_regs,
    > - sizeof(struct pt_regs));
    > + err = kvmhv_write_guest_state_and_regs(vcpu, &l2_hv, &l2_regs,
    > + hv_ptr, regs_ptr);
    > srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
    > if (err)
    > return H_AUTHORITY;

    \
     
     \ /
      Last update: 2020-12-09 15:28    [W:2.231 / U:0.920 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site