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KVM: x86/PVM: Store the valid value for MSR_PVM_VCPU_STRUCT unconditi…
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…onally

During the VM restore process, if the VMM (e.g., Cloud Hypervisor)
restores MSRs before adding the user memory region, it can result in a
failure in kvm_gpc_activate() because no memslot has been added yet. As
a consequence, the VM will panic after the VM restore since the GPC is
not active. However, if we store the value even if kvm_gpc_activate()
fails later when the GPC is active, it can be refreshed by the addition
of the user memory region before the VM entry.

Signed-off-by: Hou Wenlong <[email protected]>
Link: #2
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bysui committed Apr 2, 2024
1 parent de78abe commit 40b0ec7
Showing 1 changed file with 11 additions and 2 deletions.
13 changes: 11 additions & 2 deletions arch/x86/kvm/pvm/pvm.c
Original file line number Diff line number Diff line change
Expand Up @@ -1149,12 +1149,21 @@ static int pvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_PVM_VCPU_STRUCT:
if (!PAGE_ALIGNED(data))
return 1;
/*
* During the VM restore process, if the VMM restores MSRs
* before adding the user memory region, it can result in a
* failure in kvm_gpc_activate() because no memslot has been
* added yet. As a consequence, the VM will panic after the VM
* restore since the GPC is not active. However, if we store
* the value even if kvm_gpc_activate() fails later when the
* GPC is active, it can be refreshed by the addition of the
* user memory region before the VM entry.
*/
pvm->msr_vcpu_struct = data;
if (!data)
kvm_gpc_deactivate(&pvm->pvcs_gpc);
else if (kvm_gpc_activate(&pvm->pvcs_gpc, data, PAGE_SIZE))
return 1;

pvm->msr_vcpu_struct = data;
break;
case MSR_PVM_SUPERVISOR_RSP:
pvm->msr_supervisor_rsp = msr_info->data;
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