linux-kernel - Re: [PATCH 3/8] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED

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Message-ID: <93f6b277-fd12-71a0-3334-f92e069a9615@redhat.com>
Date:   Mon, 15 Jan 2018 10:23:53 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Longpeng (Mike)" <longpeng2@...wei.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rkrcmar@...hat.com, liran.alon@...cle.com, jmattson@...gle.com,
        aliguori@...zon.com, thomas.lendacky@....com, dwmw@...zon.co.uk,
        bp@...en8.de, x86@...nel.org, Gonglei <arei.gonglei@...wei.com>
Subject: Re: [PATCH 3/8] kvm: vmx: pass MSR_IA32_SPEC_CTRL and
 MSR_IA32_PRED_CMD down to the guest

On 13/01/2018 11:16, Longpeng (Mike) wrote:
>> +	/*
>> +	 * FIXME: this is only needed until SPEC_CTRL is supported
>> +	 * by upstream Linux in cpufeatures, then it can be replaced
>> +	 * with static_cpu_has.
>> +	 */
>> +	have_spec_ctrl = cpu_has_spec_ctrl();
>> +	if (have_spec_ctrl)
>> +		pr_info("kvm: SPEC_CTRL available\n");
>> +	else
>> +		pr_info("kvm: SPEC_CTRL not available\n");
>> +
> 
> In this approach, we must reload these modules if we update the microcode later ?

I strongly suggest using early microcode update anyway.

Paolo