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From: Paolo Bonzini <pbonzini@redhat.com>
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>
Subject: Re: [PATCH] KVM: vmx: Fix the broken usage of vmx_xsaves_supported
Date: Thu, 20 Jun 2019 10:17:29 +0200	[thread overview]
Message-ID: <b3f76acd-cc7e-9cd7-d7f7-404ba756ab87@redhat.com> (raw)
In-Reply-To: <f358c914-ae58-9889-a8ef-6ea9f3b2650e@linux.intel.com>

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

  reply	other threads:[~2019-06-20  8:17 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-20  5:03 [PATCH] KVM: vmx: Fix the broken usage of vmx_xsaves_supported Tao Xu
2019-06-20  6:40 ` Wanpeng Li
2019-06-20  6:46   ` Xiaoyao Li
2019-06-20  8:17     ` Paolo Bonzini [this message]
2019-06-20  8:27       ` Wanpeng Li
2019-06-20  8:36         ` Paolo Bonzini
2019-06-20  8:55       ` Xiaoyao Li
2019-06-20  8:59         ` Paolo Bonzini
2019-06-20  9:02           ` Wanpeng Li

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