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d="scan'208";a="14901986" To: Jan Beulich References: <20200323101724.15655-1-andrew.cooper3@citrix.com> <20200323101724.15655-8-andrew.cooper3@citrix.com> <3e157f6d-e237-68d2-f628-10f4d42e578b@citrix.com> From: Andrew Cooper Message-ID: <154fef1b-5c73-4716-e649-4ea99cba3c72@citrix.com> Date: Thu, 26 Mar 2020 14:50:47 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-GB X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To AMSPEX02CL02.citrite.net (10.69.22.126) Subject: Re: [Xen-devel] [PATCH 7/7] x86/ucode/intel: Fold structures together 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: , Cc: Xen-devel , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 26/03/2020 12:24, Jan Beulich wrote: > On 25.03.2020 15:32, Andrew Cooper wrote: >> On 25/03/2020 14:16, Jan Beulich wrote: >>> On 23.03.2020 11:17, Andrew Cooper wrote: >>>> Currently, we allocate an 8 byte struct microcode_patch to point at a >>>> separately allocated struct microcode_intel. This is wasteful. >>> As indicated elsewhere I'm very much in favor of this, but I think it >>> wants doing in one of the earlier series, and then for AMD at the same >>> time. >> I've got some ideas for an AMD series given the replies I got, and will >> be able to do an equivalent microcode_amd => microcode_patch folding on >> that side.  There is also further work to do, including unbreaking the >> OSVW logic (which has been totally clobbered by the start/end_update >> debacle). >> >> However, given that it taken this whole series to make the transition >> look safe on the Intel side, I really don't see a way of doing this >> "earlier". >> >> In particular, no amount of ifdefary suggested below can AFAICT make it >> safe to do this transform without having microcode_patch opaque to being >> with. >> >> Yes - there is a bit of churn, but I can't see a safe alternative. > Something like the one below (compile tested only, and not really > cleaned up in any way)? > > Jan Thanks.  I'll experiment with this approach. On a perhaps tangential note, what (if anything) are you plans regarding backport here? These defines are ok for a transitional period across a series (and probably means I'll need to get the AMD side ready to be committed at the same time), but I don't think we'd want them in the code for the longterm. I personally wasn't overly concerned about backports, but if you are, we should probably take this into consideration for the fixes. ~Andrew