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From: linmiaohe <linmiaohe@huawei.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"rkrcmar@redhat.com" <rkrcmar@redhat.com>,
	"sean.j.christopherson@intel.com"
	<sean.j.christopherson@intel.com>,
	"vkuznets@redhat.com" <vkuznets@redhat.com>,
	"jmattson@google.com" <jmattson@google.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>, "hpa@zytor.com" <hpa@zytor.com>
Subject: Re: [PATCH] KVM: x86: small optimization for is_mtrr_mask calculation
Date: Fri, 6 Mar 2020 02:05:40 +0000	[thread overview]
Message-ID: <82b7d2d8c75e4c80a7704ae43940392a@huawei.com> (raw)

Hi,
Paolo Bonzini <pbonzini@redhat.com> wrote:
>On 05/03/20 03:48, linmiaohe wrote:
>> From: Miaohe Lin <linmiaohe@huawei.com>
>> 
>> We can get is_mtrr_mask by calculating (msr - 0x200) % 2 directly.
>>  		index = (msr - 0x200) / 2;
>> -		is_mtrr_mask = msr - 0x200 - 2 * index;
>> +		is_mtrr_mask = (msr - 0x200) % 2;
>>  		if (!is_mtrr_mask)
>>  			*pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
>>  		else
>> 
>
>If you're going to do that, might as well use ">> 1" for index instead of "/ 2", and "msr & 1" for is_mtrr_mask.
>

Many thanks for suggestion. What do you mean is like this ?

	index = (msr - 0x200) >> 1;
	is_mtrr_mask = msr & 1;

Thanks again.

             reply	other threads:[~2020-03-06  2:05 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-06  2:05 linmiaohe [this message]
2020-03-06  2:09 ` hpa
  -- strict thread matches above, loose matches on Subject: below --
2020-03-06  2:30 linmiaohe
2020-03-06  2:22 linmiaohe
2020-03-06  2:27 ` Wanpeng Li
2020-03-05  2:48 linmiaohe
2020-03-05 14:35 ` Paolo Bonzini
2020-03-05 15:10   ` David Laight
2020-03-05 15:25     ` Paolo Bonzini

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