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

Hatayama, Daisuke
2012-10-31T09:01:08Z

> -----Original Message-----
> From: kexec-bounces@lists.infradead.org
> [mailto:kexec-bounces@lists.infradead.org] On Behalf Of zhangyanfei
> Sent: Wednesday, October 31, 2012 12:34 PM
> To: x86@kernel.org; kexec@lists.infradead.org; Avi Kivity; Marcelo
> Tosatti
> Cc: linux-kernel@vger.kernel.org; kvm@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@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