From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gioh Kim Subject: Re: [RFC] KVM: SVM: ignore type when setting segment registers Date: Tue, 30 May 2017 15:37:32 +0200 Message-ID: <20170530133730.GA23855@ws00837> References: <1496064244-14785-1-git-send-email-gi-oh.kim@profitbricks.com> <20170530125420.GA19724@potion> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: andre.przywara@amd.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Radim =?utf-8?B?S3LEjW3DocWZ?= Return-path: Content-Disposition: inline In-Reply-To: <20170530125420.GA19724@potion> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, May 30, 2017 at 02:54:21PM +0200, Radim Krčmář wrote: > 2017-05-29 15:24+0200, Gioh Kim: > > Current code sets unusable as 1 if present is 1 and type is 0. > > In Long mode, type value in segment descriptor is ignored. > > So I think type should be ignored when setting the segment registers, > > if type means the descriptor type in the segment descriptor. > > > > Is the type field of struct kvm_segment the descriptor type? > > Yes. > > > If so, why type is checked when setting segment registers? > > No idea. 19bca6ab75d8 ("KVM: SVM: Fix cross vendor migration issue with > unusable bit") also moved the assigment up to initialize it before use > and I think that is enough. > > > If the type field is not the descriptor type, > > is it ok to set unusable when present is 1? > > Looks like a bug. type = 0 can be a usable read-only data segment. > > > I'm copying a code as following to show what code I'm asking. > > Please send it as a patch, Hi Radim, Thank you for reply. I sent a patch: https://lkml.org/lkml/2017/5/30/459 I'd appreciate if if you could review it. -- Best regards, Gi-Oh Kim TEL: 0176 2697 8962