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[86.180.176.157]) by smtp.gmail.com with ESMTPSA id m67sm6887745wme.27.2021.04.22.05.34.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Apr 2021 05:34:50 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: a193514f-67be-4540-aca0-cb1a575cf820 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:reply-to:subject:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=AmBH9C2DvdJD1Qbut0x7AsSjfa7QJN90/FQP5z35c8A=; b=NPef0TvdctJ6AOx+vkiORmHfXywolN99axDxNevrsgU7MIZ3y+V+QdiYN/sY9G74jN YE6DsRpi/bllNRzo7LFZJkH/LWn8uUsUyr6H7jwB8iDWx94//6ELDi6RGqSAyoEx4i6N WyNPY0eTIn9NO3ggrmk86350tHMPrxiCqAkqVXG9Ya5adHyi9AxRi16HFYgkkcA/OS6z ZqEtZWRyocVEHBmT+mww7OS+g8h/DT9Y5a0VPfa0GJEY1isJ3iy1EubgYmEwUWpPluJA +Dkb3vh9f72XR6Wkdt+yCwii4axEcgRVR8UDbz2s2lEp+3ghts3y3Pzsj9pXZ+OowGjQ DK9A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:reply-to:subject:to:cc:references :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=AmBH9C2DvdJD1Qbut0x7AsSjfa7QJN90/FQP5z35c8A=; b=ake36ziT41AjB00zgh58k6lj8yUb+hoWQsmP9z5Bdi1KzR/bm/29U7BVD5yDOcZqdZ owuvQwEEDU1pwNgSlLizmdv2nDkSqg1O7OfgQ7TqEKEDlbtS8tAjWxZqlrK3gEby55Gt lMY8BMH/fZEZ3U2Q2jPL2OTgeWdOM/0tcAhjhlg5R2zWC8cAl51YhykwbYgWAafHN2y5 tS8svAgiGrkmWPwplms/r70BWKvrbCGhVNlQlEuAFDAYtvc/2Sjkfi8bkXg6MTUXk8M9 ZLph5c8Ji1JQPJ/S3DtnqpSrEyiXPLeJAJXSk60GoeId9AyQwsKRf7dawpdnF40WzOWf QRIg== X-Gm-Message-State: AOAM530Tpxq/olWvFnl5WdHaeoJcsmCrtgjLN/rpPHe19OEZ8ifTV63w iIhdlZlN9Bl1iWG1IdQ1L+jFmxOWEj4= X-Google-Smtp-Source: ABdhPJyqr349qli+0LIui+wStN/YEwJH7ZDXsAL5ap8ocdupdEx0SImz6TW39P2NK0d2S2EdGLg3gQ== X-Received: by 2002:a05:600c:cc:: with SMTP id u12mr3599214wmm.110.1619094891228; Thu, 22 Apr 2021 05:34:51 -0700 (PDT) From: Paul Durrant X-Google-Original-From: Paul Durrant Reply-To: paul@xen.org Subject: Re: Ping: [PATCH v3] x86/CPUID: shrink max_{,sub}leaf fields according to actual leaf contents To: Jan Beulich , Wei Liu Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , "xen-devel@lists.xenproject.org" References: <9ecd03b2-f8fa-2a8b-69ad-4b31920ea205@suse.com> <9a2058cc-d6af-d01a-8630-ab897a75ccbc@suse.com> Message-ID: <215292c9-79f6-4532-c051-0b7a0c53c138@xen.org> Date: Thu, 22 Apr 2021 13:34:50 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: <9a2058cc-d6af-d01a-8630-ab897a75ccbc@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit On 22/04/2021 12:38, Jan Beulich wrote: > On 16.04.2021 15:16, Jan Beulich wrote: >> Zapping leaf data for out of range leaves is just one half of it: To >> avoid guests (bogusly or worse) inferring information from mere leaf >> presence, also shrink maximum indicators such that the respective >> trailing entry is not all blank (unless of course it's the initial >> subleaf of a leaf that's not the final one). >> >> This is also in preparation of bumping the maximum basic leaf we >> support, to ensure guests not getting exposed related features won't >> observe a change in behavior. >> >> Signed-off-by: Jan Beulich > > First of all - I'm sorry Paul, I forgot to Cc you on the original > submission. > Ok. I did notice some discussion but wasn't really paying attention. > May I ask for an ack or otherwise for the Viridian part of this? > Please be sure, however, that you have seen the earlier discussion, > also on v2, as Roger is questioning whether the Viridian change > here wouldn't better be dropped. > I confess that I'm not a fan of the recursive calls and I do agree with Roger that limiting the leaves simply because they have zero values is probably not the right thing to do and it could lead to issues with Windows. I think, to be on the safe side, it's best to leave the viridian code as-is. Paul