Re: [PATCH 5.15.y] KVM: VMX: Flush shadow VMCS on emergency reboot

[Sean Christopherson <seanjc@google.com>]

On Thu, Jul 24, 2025, Sasha Levin wrote:
> 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>
> [ adjusted context ]
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---

Acked-by: Sean Christopherson <seanjc@google.com>