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[54.240.197.238]) by smtp.gmail.com with ESMTPSA id b2sm2884607ejv.61.2020.04.06.03.34.40 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Apr 2020 03:34:41 -0700 (PDT) From: Paul Durrant X-Google-Original-From: "Paul Durrant" To: "'Julien Grall'" , References: <20200327185012.1795-1-paul@xen.org> <20200327185012.1795-2-paul@xen.org> <5a26a89a-6422-b41d-daac-8f33a48ae23b@xen.org> <002201d609d0$55a76690$00f633b0$@xen.org> <001701d60bed$25606f80$70214e80$@xen.org> <002701d60bf4$4b640460$e22c0d20$@xen.org> In-Reply-To: Subject: RE: [PATCH 1/5] xen/common: introduce a new framework for save/restore of 'domain' context Date: Mon, 6 Apr 2020 11:34:39 +0100 Message-ID: <002801d60bfe$fab5de70$f0219b50$@xen.org> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Content-Language: en-gb Thread-Index: AQG3I8TZM/MLMEc/e2It3WEXPZVs8AC9qttvAt7KY/0Cn78SegKGUxSNAT1JVvEC2KVtyQKYWtbpAi2RjHuoHMJVgA== X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Reply-To: paul@xen.org Cc: 'Stefano Stabellini' , 'Wei Liu' , 'Andrew Cooper' , 'Ian Jackson' , 'George Dunlap' , 'Jan Beulich' Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" > -----Original Message----- [snip] > >> * The name of the hypercall does not say anything about "PV". So a > >> contributor could think it would be fine to save/restore new HVM state > >> in the new generic hypercall. Is it going to be an issue? If so, how do > >> we prevent it? > > > > The commit message says: > > > > "Domain context is state held in the hypervisor that does not come under > > the category of 'HVM state' but is instead 'PV state' that is common > > between PV guests and enlightened HVM guests (i.e. those that have PV > > drivers) such as event channel state, grant entry state, etc." > > This does not seem to cover all the cases. For instance, where would you > save IOREQ servers information? > Ok, I agree that is ambiguous. I'd still call it PV state but of course it does only relate to HVM guests. > > > > Do you think this should also appear in a comment? Do we really care? Nothing fundamentally prevents > the mechanism being used for HVM state, but that may introduce an ordering dependency. > > I don't particularly like the idea to let the contributor decide where > "HVM context" or as part of the "Domain context". > > This is going to result to unwanted dependency and possibly > bikeshedding on where they should be saved. > > My preference would be to mark the existing framework as deprecated and > force all the new states to be saved as part of the new "Domain Context". > I'm ok with that. Any others have any opinion to the contrary? > > > >> * Are we going to deprecate the existing framework? > >> > > > > There is no intention as yet. > > > >> I am not suggesting we should not go with two frameworks, but the > >> reasons and implications are not clear to me. Hence, why I think the > >> commit message should be expanded with some rationale. > >> > > > > Ok, I can add a paragraph to try to explain a little more. > > That would be appreciated. Thank you! > I'll mention the deprecation of the HVM context interface there too. Paul