[PATCH 6.1.y 3/3] KVM: VMX: Flush shadow VMCS on emergency reboot

[Sasha Levin <sashal@kernel.org>]

From: Chao Gao <chao.gao@intel.com>

[ Upstream commit a0ee1d5faff135e28810f29e0f06328c66f89852 ]

Ensure the shadow VMCS cache is evicted during an emergency reboot to
prevent potential memory corruption if the cache is evicted after reboot.

This issue was identified through code inspection, as __loaded_vmcs_clear()
flushes both the normal VMCS and the shadow VMCS.

Avoid checking the "launched" state during an emergency reboot, unlike the
behavior in __loaded_vmcs_clear(). This is important because reboot NMIs
can interfere with operations like copy_shadow_to_vmcs12(), where shadow
VMCSes are loaded directly using VMPTRLD. In such cases, if NMIs occur
right after the VMCS load, the shadow VMCSes will be active but the
"launched" state may not be set.

Fixes: 16f5b9034b69 ("KVM: nVMX: Copy processor-specific shadow-vmcs to VMCS12")
Cc: stable@vger.kernel.org
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20250324140849.2099723-1-chao.gao@intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kvm/vmx/vmx.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index ef9cb8445dc48..12f9b220b6bd1 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -711,8 +711,11 @@ static void vmx_emergency_disable(void)
 	struct loaded_vmcs *v;
 
 	list_for_each_entry(v, &per_cpu(loaded_vmcss_on_cpu, cpu),
-			    loaded_vmcss_on_cpu_link)
+			    loaded_vmcss_on_cpu_link) {
 		vmcs_clear(v->vmcs);
+		if (v->shadow_vmcs)
+			vmcs_clear(v->shadow_vmcs);
+	}
 
 	__cpu_emergency_vmxoff();
 }
-- 
2.39.5