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KVM: x86: nSVM: refactor svm_leave_smm and smm_enter_smm
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Use return statements instead of nested if, and fix error
path to free all the maps that were allocated.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210913140954.165665-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Maxim Levitsky authored and Paolo Bonzini committed Sep 22, 2021
1 parent e85d3e7 commit 136a55c
Showing 1 changed file with 69 additions and 66 deletions.
135 changes: 69 additions & 66 deletions arch/x86/kvm/svm/svm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4285,96 +4285,99 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
struct kvm_host_map map_save;
int ret;

if (is_guest_mode(vcpu)) {
/* FED8h - SVM Guest */
put_smstate(u64, smstate, 0x7ed8, 1);
/* FEE0h - SVM Guest VMCB Physical Address */
put_smstate(u64, smstate, 0x7ee0, svm->nested.vmcb12_gpa);
if (!is_guest_mode(vcpu))
return 0;

svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];
svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP];
svm->vmcb->save.rip = vcpu->arch.regs[VCPU_REGS_RIP];
/* FED8h - SVM Guest */
put_smstate(u64, smstate, 0x7ed8, 1);
/* FEE0h - SVM Guest VMCB Physical Address */
put_smstate(u64, smstate, 0x7ee0, svm->nested.vmcb12_gpa);

ret = nested_svm_vmexit(svm);
if (ret)
return ret;
svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];
svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP];
svm->vmcb->save.rip = vcpu->arch.regs[VCPU_REGS_RIP];

/*
* KVM uses VMCB01 to store L1 host state while L2 runs but
* VMCB01 is going to be used during SMM and thus the state will
* be lost. Temporary save non-VMLOAD/VMSAVE state to the host save
* area pointed to by MSR_VM_HSAVE_PA. APM guarantees that the
* format of the area is identical to guest save area offsetted
* by 0x400 (matches the offset of 'struct vmcb_save_area'
* within 'struct vmcb'). Note: HSAVE area may also be used by
* L1 hypervisor to save additional host context (e.g. KVM does
* that, see svm_prepare_guest_switch()) which must be
* preserved.
*/
if (kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.hsave_msr),
&map_save) == -EINVAL)
return 1;
ret = nested_svm_vmexit(svm);
if (ret)
return ret;

/*
* KVM uses VMCB01 to store L1 host state while L2 runs but
* VMCB01 is going to be used during SMM and thus the state will
* be lost. Temporary save non-VMLOAD/VMSAVE state to the host save
* area pointed to by MSR_VM_HSAVE_PA. APM guarantees that the
* format of the area is identical to guest save area offsetted
* by 0x400 (matches the offset of 'struct vmcb_save_area'
* within 'struct vmcb'). Note: HSAVE area may also be used by
* L1 hypervisor to save additional host context (e.g. KVM does
* that, see svm_prepare_guest_switch()) which must be
* preserved.
*/
if (kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.hsave_msr),
&map_save) == -EINVAL)
return 1;

BUILD_BUG_ON(offsetof(struct vmcb, save) != 0x400);
BUILD_BUG_ON(offsetof(struct vmcb, save) != 0x400);

svm_copy_vmrun_state(map_save.hva + 0x400,
&svm->vmcb01.ptr->save);
svm_copy_vmrun_state(map_save.hva + 0x400,
&svm->vmcb01.ptr->save);

kvm_vcpu_unmap(vcpu, &map_save, true);
}
kvm_vcpu_unmap(vcpu, &map_save, true);
return 0;
}

static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
{
struct vcpu_svm *svm = to_svm(vcpu);
struct kvm_host_map map, map_save;
int ret = 0;
u64 saved_efer, vmcb12_gpa;
struct vmcb *vmcb12;
int ret;

if (guest_cpuid_has(vcpu, X86_FEATURE_LM)) {
u64 saved_efer = GET_SMSTATE(u64, smstate, 0x7ed0);
u64 guest = GET_SMSTATE(u64, smstate, 0x7ed8);
u64 vmcb12_gpa = GET_SMSTATE(u64, smstate, 0x7ee0);
struct vmcb *vmcb12;
if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
return 0;

if (guest) {
if (!guest_cpuid_has(vcpu, X86_FEATURE_SVM))
return 1;
/* Non-zero if SMI arrived while vCPU was in guest mode. */
if (!GET_SMSTATE(u64, smstate, 0x7ed8))
return 0;

if (!(saved_efer & EFER_SVME))
return 1;
if (!guest_cpuid_has(vcpu, X86_FEATURE_SVM))
return 1;

if (kvm_vcpu_map(vcpu,
gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)
return 1;
saved_efer = GET_SMSTATE(u64, smstate, 0x7ed0);
if (!(saved_efer & EFER_SVME))
return 1;

if (svm_allocate_nested(svm))
return 1;
vmcb12_gpa = GET_SMSTATE(u64, smstate, 0x7ee0);
if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)
return 1;

kvm_vcpu_unmap(vcpu, &map, true);
ret = 1;
if (kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.hsave_msr), &map_save) == -EINVAL)
goto unmap_map;

/*
* Restore L1 host state from L1 HSAVE area as VMCB01 was
* used during SMM (see svm_enter_smm())
*/
if (kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.hsave_msr),
&map_save) == -EINVAL)
return 1;
if (svm_allocate_nested(svm))
goto unmap_save;

svm_copy_vmrun_state(&svm->vmcb01.ptr->save,
map_save.hva + 0x400);
/*
* Restore L1 host state from L1 HSAVE area as VMCB01 was
* used during SMM (see svm_enter_smm())
*/

/*
* Enter the nested guest now
*/
vmcb12 = map.hva;
nested_load_control_from_vmcb12(svm, &vmcb12->control);
ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12, false);
svm_copy_vmrun_state(&svm->vmcb01.ptr->save, map_save.hva + 0x400);

kvm_vcpu_unmap(vcpu, &map_save, true);
}
}
/*
* Enter the nested guest now
*/

vmcb12 = map.hva;
nested_load_control_from_vmcb12(svm, &vmcb12->control);
ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12, false);

unmap_save:
kvm_vcpu_unmap(vcpu, &map_save, true);
unmap_map:
kvm_vcpu_unmap(vcpu, &map, true);
return ret;
}

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