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Peter Anvin" , linux-kernel@vger.kernel.org References: <20210903102039.55422-1-eesposit@redhat.com> <20210903102039.55422-4-eesposit@redhat.com> <21d2bf8c4e3eb3fc5d297fd13300557ec686b625.camel@redhat.com> <73b5a5bb-48f2-3a08-c76b-a82b5b69c406@redhat.com> <9585f1387b2581d30b74cd163a9aac2adbd37a93.camel@redhat.com> <2b1e17416cef1e37f42e9bc8b2283b03d2651cb2.camel@redhat.com> From: Emanuele Giuseppe Esposito Message-ID: Date: Tue, 14 Sep 2021 11:24:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <2b1e17416cef1e37f42e9bc8b2283b03d2651cb2.camel@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/09/2021 11:12, Maxim Levitsky wrote: > On Tue, 2021-09-14 at 12:02 +0300, Maxim Levitsky wrote: >> On Tue, 2021-09-14 at 10:20 +0200, Emanuele Giuseppe Esposito wrote: >>> On 12/09/2021 12:42, Maxim Levitsky wrote: >>>>> >>>>> - if (!nested_vmcb_valid_sregs(vcpu, &vmcb12->save) || >>>>> + if (!nested_vmcb_valid_sregs(vcpu, &svm->nested.save) || >>>>> !nested_vmcb_check_controls(vcpu, &svm->nested.ctl)) { >>>> If you use a different struct for the copied fields, then it makes >>>> sense IMHO to drop the 'control' parameter from nested_vmcb_check_controls, >>>> and just use the svm->nested.save there directly. >>>> >>> >>> Ok, what you say in patch 2 makes sense to me. I can create a new struct >>> vmcb_save_area_cached, but I need to keep nested.ctl because 1) it is >>> used also elsewhere, and different fields from the one checked here are >>> read/set and 2) using another structure (or the same >> >> Yes, keep nested.ctl, since vast majority of the fields are copied I think. > > But actually that you mention it, I'll say why not to create vmcb_control_area_cached > as well indeed and change the type of svm->nested.save to it. (in a separate patch) > > I see what you mean that we modify it a bit (but we shoudn't to be honest) and such, but > all of this can be fixed. So basically you are proposing: struct svm_nested_state { ... struct vmcb_control_area ctl; // we need this because it is used everywhere, I think struct vmcb_control_area_cached ctl_cached; struct vmcb_save_area_cached save_cached; ... } and then if (!nested_vmcb_valid_sregs(vcpu, &svm->nested.save_cached) || !nested_vmcb_check_controls(vcpu, &svm->nested.ctl_cached)) { like that? Or do you want to delete nested.ctl completely and just keep the fields actually used in ctl_cached? Also, note that as I am trying to use vmcb_save_area_cached, it is worth noticing that nested_vmcb_valid_sregs() is also used in svm_set_nested_state(), so it requires some additional little changes. Thank you, Emanuele > > The advantage of having vmcb_control_area_cached is that it becomes impossible to use > by mistake a non copied field from the guest. > > It would also emphasize that this stuff came from the guest and should be treated as > a toxic waste. > > Note again that this should be done if we agree as a separate patch. > >> >> Best regards, >> Maxim Levitsky >> >> >>> vmcb_save_area_cached) in its place would just duplicate the same fields >>> of nested.ctl, creating even more confusion and possible inconsistency. >>> >>> Let me know if you disagree. >>> >>> Thank you, >>> Emanuele >>> > >