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From: Paolo Bonzini <pbonzini@redhat.com>
To: peng.hao2@zte.com.cn
Cc: rkrcmar@redhat.com, tglx@linutronix.de, mingo@redhat.com,
	hpa@zytor.com, x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kvm: x86: reduce rtc 0x70 access vm-exit time
Date: Wed, 2 Aug 2017 12:06:37 +0200	[thread overview]
Message-ID: <079b077b-a0e8-7c93-62d6-62abc67168b3@redhat.com> (raw)
In-Reply-To: <201708021702599158875@zte.com.cn>

On 02/08/2017 11:02, peng.hao2@zte.com.cn wrote:
> 
>> On 02/08/2017 10:45, peng.hao2@zte.com.cn wrote:
>> >>On 02/08/2017 17:24, Peng Hao wrote:
>> > coalesced MMIO is async and io port should be sync .  I don't need to
>> > coalese io port access.
> 
>> Coalesced MMIO access is resolved on the next read from a coalesced MMIO
>> address or the next write to a non-coalescecd MMIO address.  So it would
>> work perfectly for port 0x70.  You would have to modify QEMU to split
>> the RTC I/O ports into two MemoryRegions.
>
> ok , it sounds simpler. I will try it.

My suggestion is to repurpose the "pad" field of "struct
kvm_coalesced_mmio_zone" to be 0 for memory and -1 for I/O.  It should
be enough for an RFC.

Later we can look into how to handle backwards compatibility.

Thanks,

Paolo

       reply	other threads:[~2017-08-02 10:06 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <201708021702599158875@zte.com.cn>
2017-08-02 10:06 ` Paolo Bonzini [this message]
2017-08-02 15:24 [PATCH] kvm: x86: reduce rtc 0x70 access vm-exit time Peng Hao
2017-08-02  7:50 ` Paolo Bonzini
     [not found] <201708021645519197745@zte.com.cn>
2017-08-02  8:50 ` Paolo Bonzini

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