[PATCH v3 2/2] KVM: make crash_clear_loaded_vmcss valid when loading kvm_intel module

[Hatayama, Daisuke]

> -----Original Message-----
> From: kexec-bounces at lists.infradead.org
> [mailto:kexec-bounces at lists.infradead.org] On Behalf Of zhangyanfei
> Sent: Wednesday, October 31, 2012 12:34 PM
> To: x86 at kernel.org; kexec at lists.infradead.org; Avi Kivity; Marcelo
> Tosatti
> Cc: linux-kernel at vger.kernel.org; kvm at vger.kernel.org
> Subject: [PATCH v3 2/2] KVM: make crash_clear_loaded_vmcss valid when
> loading kvm_intel module
> 
> Signed-off-by: Zhang Yanfei <zhangyanfei at cn.fujitsu.com>

[...]

> @@ -7230,6 +7231,10 @@ static int __init vmx_init(void)
>  	if (r)
>  		goto out3;
> 
> +#ifdef CONFIG_KEXEC
> +	crash_clear_loaded_vmcss = vmclear_local_loaded_vmcss;
> +#endif
> +

Assignment here cannot cover the case where NMI is initiated after VMX is on in kvm_init and before vmclear_local_loaded_vmcss is assigned, though rare but can happen.

What does happen if calling vmclear_local_loaded_vmcss before kvm_init? I think it no problem since the list is initially empty.

>  	vmx_disable_intercept_for_msr(MSR_FS_BASE, false);
>  	vmx_disable_intercept_for_msr(MSR_GS_BASE, false);
>  	vmx_disable_intercept_for_msr(MSR_KERNEL_GS_BASE, true);
> @@ -7265,6 +7270,10 @@ static void __exit vmx_exit(void)
>  	free_page((unsigned long)vmx_io_bitmap_b);
>  	free_page((unsigned long)vmx_io_bitmap_a);
> 
> +#ifdef CONFIG_KEXEC
> +	crash_clear_loaded_vmcss = NULL;
> +#endif
> +
>  	kvm_exit();
>  }

Also, this is converse to the above.

Thanks.
HATAYAMA, Daisuke