From: "Jan Beulich" <jbeulich@suse.com> To: andrew.cooper3@citrix.com Cc: xen-devel@lists.xenproject.org, kevin.tian@intel.com, wei.liu2@citrix.com, jun.nakajima@intel.com, roger.pau@citrix.com Subject: Re: [PATCH v2] x86/msr: Fix fallout from mostly c/s 832c180 Date: Mon, 15 Apr 2019 09:49:29 -0600 [thread overview] Message-ID: <5CB4A8090200007800155576@prv1-mh.provo.novell.com> (raw) In-Reply-To: <1555329809-3248-1-git-send-email-andrew.cooper3@citrix.com> >>> Andrew Cooper <andrew.cooper3@citrix.com> 04/15/19 2:03 PM >>> >* Fix the shim build by providing a !CONFIG_HVM declaration for >hvm_get_guest_bndcfgs(), and removing the introduced >ASSERT(is_hvm_domain(d))'s. They are needed for DCE to keep the build >working. Furthermore, in this way, the risk of runtime type confusion is >removed. >* Revert the de-const'ing of the vcpu pointer in vmx_get_guest_bndcfgs(). >vmx_vmcs_enter() really does mutate the vcpu, and may cause it to undergo a >full de/reschedule, which is in violation of the ABI described by >hvm_get_guest_bndcfgs(). guest_rdmsr() was always going to need to lose >its const parameter, and this was the correct time for it to happen. With the ABI violation claim here removed (e.g. replaced by saying that it might be confusing to the reader) Acked-by: Jan Beulich <jbeulich@suse.com> This wrong (at least I continue to be of the opinion that it is) claim - just to make it explicit - is what I've previously called being factual incorrect on the v1 thread. As said before, there's no "ABI promise" to be derived from "const". In fact I'd prefer VMCS reads in general to be viewed as reading "state", not memory, and it just so happens that in certain cases some syncing between memory and CPU needs to be done for correct "state" to be returned. This doesn't alter what the caller sees (i.e. there's no change to "state", and any locks acquired get released again before returning). I'd like to re-emphasize the similarity to C++'s mutable here. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
WARNING: multiple messages have this Message-ID (diff)
From: "Jan Beulich" <jbeulich@suse.com> To: <andrew.cooper3@citrix.com> Cc: xen-devel@lists.xenproject.org, kevin.tian@intel.com, wei.liu2@citrix.com, jun.nakajima@intel.com, roger.pau@citrix.com Subject: Re: [Xen-devel] [PATCH v2] x86/msr: Fix fallout from mostly c/s 832c180 Date: Mon, 15 Apr 2019 09:49:29 -0600 [thread overview] Message-ID: <5CB4A8090200007800155576@prv1-mh.provo.novell.com> (raw) Message-ID: <20190415154929.4BAgJrgTXx0C1MMeVLy73uI2287r6Wotj1b9fQ7Fyuc@z> (raw) In-Reply-To: <1555329809-3248-1-git-send-email-andrew.cooper3@citrix.com> >>> Andrew Cooper <andrew.cooper3@citrix.com> 04/15/19 2:03 PM >>> >* Fix the shim build by providing a !CONFIG_HVM declaration for >hvm_get_guest_bndcfgs(), and removing the introduced >ASSERT(is_hvm_domain(d))'s. They are needed for DCE to keep the build >working. Furthermore, in this way, the risk of runtime type confusion is >removed. >* Revert the de-const'ing of the vcpu pointer in vmx_get_guest_bndcfgs(). >vmx_vmcs_enter() really does mutate the vcpu, and may cause it to undergo a >full de/reschedule, which is in violation of the ABI described by >hvm_get_guest_bndcfgs(). guest_rdmsr() was always going to need to lose >its const parameter, and this was the correct time for it to happen. With the ABI violation claim here removed (e.g. replaced by saying that it might be confusing to the reader) Acked-by: Jan Beulich <jbeulich@suse.com> This wrong (at least I continue to be of the opinion that it is) claim - just to make it explicit - is what I've previously called being factual incorrect on the v1 thread. As said before, there's no "ABI promise" to be derived from "const". In fact I'd prefer VMCS reads in general to be viewed as reading "state", not memory, and it just so happens that in certain cases some syncing between memory and CPU needs to be done for correct "state" to be returned. This doesn't alter what the caller sees (i.e. there's no change to "state", and any locks acquired get released again before returning). I'd like to re-emphasize the similarity to C++'s mutable here. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
next prev parent reply other threads:[~2019-04-15 15:45 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-04-15 12:03 [PATCH v2] x86/msr: Fix fallout from mostly c/s 832c180 Andrew Cooper 2019-04-15 12:03 ` [Xen-devel] " Andrew Cooper 2019-04-15 15:49 ` Jan Beulich [this message] 2019-04-15 15:49 ` Jan Beulich 2019-04-16 10:53 ` Paul Durrant 2019-04-16 10:53 ` [Xen-devel] " Paul Durrant 2019-04-24 6:46 ` Tian, Kevin 2019-04-24 6:46 ` [Xen-devel] " Tian, Kevin
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