linux-kernel - Re: [PATCH v2 1/4] KVM: x86: use new CS.RPL as CPL during task switch

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Message-ID: <20140526165518.GB30582@amt.cnet>
Date:	Mon, 26 May 2014 13:55:18 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, jan.kiszka@...mens.com,
	kvm@...r.kernel.org, gleb@...nel.org, avi.kivity@...il.com
Subject: Re: [PATCH v2 1/4] KVM: x86: use new CS.RPL as CPL during task switch

On Thu, May 15, 2014 at 06:51:28PM +0200, Paolo Bonzini wrote:
> During task switch, all of CS.DPL, CS.RPL, SS.DPL must match (in addition
> to all the other requirements) and will be the new CPL.  So far this
> worked by carefully setting the CS selector and flag before doing the
> task switch; however, this will not work once we get the CPL from SS.DPL:
> setting SS itself would fail if the task switch changes the privilege
> level.
> 
> Temporarily assume that the CPL comes from CS.RPL during task switch
> to a protected-mode task.  This is the same approach used in QEMU's
> emulation code, which (until version 2.0) manually tracks the CPL.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Reviewed-by: Marcelo Tosatti <mtosatti@...hat.com>

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