linux-kernel - Query regarding Spectre fixes for qemu-kvm...4.4 LTS Kernel.

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Message-ID: <AT5PR8401MB1138DE66FC69195F3F2A9886B8AF0@AT5PR8401MB1138.NAMPRD84.PROD.OUTLOOK.COM>
Date:   Tue, 4 Dec 2018 04:11:31 +0000
From:   "Arackal, Paulose Kuriakose (STSD)" 
        <paulose.kuriakose.arackal@....com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Query regarding Spectre fixes for qemu-kvm...4.4 LTS Kernel.

Hi,

I have few queries regarding qemu-kvm support of Spectre related fixes at 4.4.* LTS Kernel.

I see that in upstream kernels, svm_vcpu_run() calls  x86_spec_ctrl_set_guest() and  x86_spec_ctrl_restore_host().
And calling into x86_virt_spec_ctrl(), that sets IBRS/IBPB/SSBD bits accordingly for guest context.

Related commit IDs below:
commit 5cf687548705412da47c9cec342fd952d71ed3d5
commit ccbcd2674472a978b48c91c1fbfb66c0ff959f24

Looks like this change is not fully ported to 4.4 LTS yet. 
x86_spec_ctrl_set_guest() and  x86_spec_ctrl_restore_host() interfaces are available, however looks like  svm_vcpu_run() is not calling them.  
So qemu-kvm running on 4.4 kernels may not have SPEC_CTRL set properly in guest context.

Is there a plan to backport above changes fully into 4.4 LTS kernel?.

Thanks,
Paulose.