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x86/kvm/nVMX: fix VMCLEAR when Enlightened VMCS is in use

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When Enlightened VMCS is in use, it is valid to do VMCLEAR and,
according to TLFS, this should "transition an enlightened VMCS from the
active to the non-active state". It is, however, wrong to assume that
it is only valid to do VMCLEAR for the eVMCS which is currently active
on the vCPU performing VMCLEAR.

Currently, the logic in handle_vmclear() is broken: in case, there is no
active eVMCS on the vCPU doing VMCLEAR we treat the argument as a 'normal'
VMCS and kvm_vcpu_write_guest() to the 'launch_state' field irreversibly
corrupts the memory area.

So, in case the VMCLEAR argument is not the current active eVMCS on the
vCPU, how can we know if the area it is pointing to is a normal or an
enlightened VMCS?
Thanks to the bug in Hyper-V (see commit 72aeb60c52 ("KVM: nVMX: Verify
eVMCS revision id match supported eVMCS version on eVMCS VMPTRLD")) we can
not, the revision can't be used to distinguish between them. So let's
assume it is always enlightened in case enlightened vmentry is enabled in
the assist page. Also, check if vmx->nested.enlightened_vmcs_enabled to
minimize the impact for 'unenlightened' workloads.

Fixes: b8bbab928f ("KVM: nVMX: implement enlightened VMPTRLD and VMCLEAR")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov
2019-06-28 13:23:33 +02:00
committed by Paolo Bonzini
parent a21a39c206
commit 11e349143e
3 changed files with 37 additions and 14 deletions
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18
arch/x86/kvm/vmx/evmcs.c
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@@ -3,6 +3,7 @@
#include <linux/errno.h>
#include <linux/smp.h>
#include "../hyperv.h"
#include "evmcs.h"
#include "vmcs.h"
#include "vmx.h"
@@ -313,6 +314,23 @@ void evmcs_sanitize_exec_ctrls(struct vmcs_config *vmcs_conf)
}
#endif
bool nested_enlightened_vmentry(struct kvm_vcpu *vcpu, u64 *evmcs_gpa)
{
struct hv_vp_assist_page assist_page;
*evmcs_gpa = -1ull;
if (unlikely(!kvm_hv_get_assist_page(vcpu, &assist_page)))
return false;
if (unlikely(!assist_page.enlighten_vmentry))
return false;
*evmcs_gpa = assist_page.current_nested_vmcs;
return true;
}
uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);