Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] KVM: vmx: Fix the broken usage of vmx_xsaves_supported
To:     Xiaoyao Li <xiaoyao.li@linux.intel.com>,
        Wanpeng Li <kernellwp@gmail.com>, Tao Xu <tao3.xu@intel.com>
Cc:     Radim Krcmar <rkrcmar@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, kvm <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20190620050301.1149-1-tao3.xu@intel.com>
 <CANRm+Cwg7ogTN1w=xNyn+8CfxwofdxRykULFe217pXidzEhh6Q@mail.gmail.com>
 <f358c914-ae58-9889-a8ef-6ea9f3b2650e@linux.intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <b3f76acd-cc7e-9cd7-d7f7-404ba756ab87@redhat.com>
Date:   Thu, 20 Jun 2019 10:17:29 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.6.1
MIME-Version: 1.0
In-Reply-To: <f358c914-ae58-9889-a8ef-6ea9f3b2650e@linux.intel.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 20/06/19 08:46, Xiaoyao Li wrote:
>>
>> It depends on whether or not processors support the 1-setting instead
>> of “enable XSAVES/XRSTORS” is 1 in VM-exection control field. Anyway,
> 
> Yes, whether this field exist or not depends on whether processors
> support the 1-setting.
> 
> But if "enable XSAVES/XRSTORS" is clear to 0, XSS_EXIT_BITMAP doesn't
> work. I think in this case, there is no need to set this vmcs field?

vmx->secondary_exec_control can change; you are making the code more
complex by relying on the value of the field at the point of vmx_vcpu_setup.

I do _think_ your version is incorrect, because at this point CPUID has
not been initialized yet and therefore
vmx_compute_secondary_exec_control has not set SECONDARY_EXEC_XSAVES.
However I may be wrong because I didn't review the code very closely:
the old code is obvious and so there is no point in changing it.

Paolo