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KVM: PPC: Book3S HV: Allow nested guest creation when L0 hv_guest_state > L1

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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 loosened up a bit. L0 can be taught to
understand older layout of hv_guest_state, if we restrict the
new members 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>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Ravi Bangoria 2020-12-16 16:12:16 +05:30 committed by Paul Mackerras
parent 9294b8a125
commit afe7504930
2 changed files with 60 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
arch/powerpc/include/asm/hvcall.h
View File

@ -535,9 +535,12 @@ 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) */
@ -571,6 +574,16 @@ 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;
}
}
/*
* From the document "H_GetPerformanceCounterInfo Interface" v1.07
*

55
arch/powerpc/kvm/book3s_hv_nested.c
View File

@ -215,12 +215,51 @@ 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;
struct kvm_nested_guest *l2;
struct pt_regs l2_regs, saved_l1_regs;
struct hv_guest_state l2_hv, saved_l1_hv;
struct hv_guest_state l2_hv = {0}, saved_l1_hv;
struct kvmppc_vcore *vc = vcpu->arch.vcore;
u64 hv_ptr, regs_ptr;
u64 hdec_exp;
@ -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;