linux-kernel - Re: [PATCH v2 6/6] Describe KVM_MSR_STEAL

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4D456555.2030606@redhat.com>
Date:	Sun, 30 Jan 2011 15:19:17 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Glauber Costa <glommer@...hat.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	aliguori@...ibm.com
Subject: Re: [PATCH v2 6/6] Describe KVM_MSR_STEAL_TIME

On 01/28/2011 09:52 PM, Glauber Costa wrote:
> This patch adds documentation about usage of the newly
> introduced KVM_MSR_STEAL_TIME.
>
>
> +
> +MSR_KVM_STEAL_TIME: 0x4b564d03
> +
> +	data: 4-byte alignment physical address of a memory area which must be
> +	in guest RAM, plus an enable bit in bit 0.

64-byte aligned:
- avoids wrapping around a page boundary, which may let us optimize 
things later on (see kvm_write_guest_cached()).
- gives us 5 more unused bits to enable more options

>   This memory is expected to
> +	hold a copy of the following structure:
> +
> +	struct kvm_steal_time {
> +	  	__u64 steal;
> + 		__u32 version;
> + 		__u32 flags;
> +	 	__u32 pad[6];
> +	}
> +
> +	whose data will be filled in by the hypervisor periodically. Only one
> +	write, or registration, is needed for each VCPU. The interval between
> +	updates of this structure is arbitrary and implementation-dependent.
> +	The hypervisor may update this structure at any time it sees fit until
> +	anything with bit0 == 0 is written to it.
> +
> +	Fields have the following meanings:
> +
> +		version: guest has to check version before and after grabbing
> +		time information and check that they are both equal and even.
> +		An odd version indicates an in-progress update.
> +
> +		flags: At this point, always zero. May be used to indicate
> +		changes in this structure in the future.
> +
> +		steal: the amount of time in which this vCPU did not run, in
> +		nanoseconds.
> +

The guest must initialize the entire 64-byte structure to zero before 
enabling the feature.

-- 
error compiling committee.c: too many arguments to function

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/