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[92.178.7.112]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3a6e8117187sm6429439f8f.101.2025.06.26.00.49.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Jun 2025 00:49:21 -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: 12821cea-5262-11f0-a30f-13f23c93f187 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1750924161; x=1751528961; darn=lists.xenproject.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=N2eBZ73J800zS0COuSSb7WwAu4nL1GCeHQjgrI24kL4=; b=BLUyqqfkkrE7h+Vw2RnLLdg7LMtCDL/2zwgznBry6ZyN7LpMEnZz/g1BzNlA6re8R3 YoU1JwHOmAS9Ow8J/5PWlf5fKCEhkHZ9gLMYUZy6+H4xDBsahNXSlnBb7km3ziF1MMd/ eERfPxmQlwaSj+4VjFqIxayOH8NwqmQwSIOw8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750924161; x=1751528961; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=N2eBZ73J800zS0COuSSb7WwAu4nL1GCeHQjgrI24kL4=; b=DuBYkVbihlfLTi6k4gYHQaBqVaa197ICkpVVrsc5EE89upSTrIBbH1U4Q0yQhb+GUb gcs25vcoiBpR1XBGSjfJzFEEdgvl8OnAMPGP5XGrPIHae53S70a446nawmF8eLp3PO3K 0KZvTFOBKoctQMfsYHgPiY2sczdpdEmmBHlo5zdE3LDPYSlVpdOaToTBOPoMFDMXU6QN ZR1NzFhC1bjPFgMIj3kdyQXdeH2147+iK+AbBif6Xzemdg6CuX0X49deFZdJrq9il98g 6FO9xOPS+EIPAOB4URdq7BWgIxI1wasBRHhRUFZRl5QGU34uxPbCi7rd36pzj/EhLrVR OuCQ== X-Forwarded-Encrypted: i=1; AJvYcCWt3HNzH77xHN1HclcJL3z76jD02bZGF+4nEdWg1D/HJBu7KtmgwraZqqW2b4Dum5rxfF/AHUhDTYQ=@lists.xenproject.org X-Gm-Message-State: AOJu0YwIhB6NDY15UFMs8sQt8JT7bHBU16xYdriimvEW6S6Z+jncrdyS 9UKx8zSpoJwd9WmghhJobWWpoIUAa9nDuV9Ndbw4eDJB5OLIAMGSHi3SSMBan2gjdT4= X-Gm-Gg: ASbGncunn68UIX1lnACNLqufZmOJ5Hg/YWFCYomGYlHT5cvrx8dMabATeZqsN8OnQW/ 00TGjrTVmt//au5O23sJeGxAftGxTz7PSge25wcpBvPPBt5MlFP0OHnD1x9+0PkHRGSTL7F4lf5 epKxB/Z5nMrrCazuHfZdnWAoiOAoJ+ouq44WW9DSOdRekYohUJQprl0oi9uJip9ZL/3m1A8nvNG SWXZLDqAgltAJF+v98yP6njVZNFMKTWUuf1iQJrsEFDPgA7QVSjMOOgvz31kK3Kj2EVk48ShPPm jUpHHOGqypo2bJNX8eJkVz8HdrnpfGiv8sLFnv1tIOJgNazPH+1IlY23lfAQkQ9tobtT1BELdWd 3wvzNgemUQZIPh/5lnqfUJpeWYN6/1zEDafGVGt1f0GbNSQ== X-Google-Smtp-Source: AGHT+IEX8T0o9JAt/xqkiCO4Z4Di1M0dnj4pP/mnuAu8IsEmIwPyUZom3xaz9I61nrm4fV9WdYOIwg== X-Received: by 2002:a05:600c:4684:b0:450:cea0:1781 with SMTP id 5b1f17b1804b1-45381ae456bmr62138925e9.16.1750924161364; Thu, 26 Jun 2025 00:49:21 -0700 (PDT) Date: Thu, 26 Jun 2025 09:49:20 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , Stefano Stabellini , xen-devel@lists.xenproject.org Subject: Re: [PATCH v2 2/8] kconfig: turn PDX compression into a choice Message-ID: References: <20250620111130.29057-1-roger.pau@citrix.com> <20250620111130.29057-3-roger.pau@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Tue, Jun 24, 2025 at 03:13:27PM +0200, Jan Beulich wrote: > On 20.06.2025 13:11, Roger Pau Monne wrote: > > Rename the current CONFIG_PDX_COMPRESSION to CONFIG_PDX_MASK_COMPRESSION, > > and make it part of the PDX compression choice block, in preparation for > > adding further PDX compression algorithms. > > > > No functional change intended as the PDX compression defaults should still > > be the same for all architectures, however the choice block cannot be > > protected under EXPERT and still have a default choice being > > unconditionally selected. As a result, the new "PDX (Page inDeX) > > compression" item will be unconditionally visible in Kconfig. > > Just to mention it: Afaict there is a functional change, but one I actually > appreciate, at least in part. So far ... > > > --- a/xen/common/Kconfig > > +++ b/xen/common/Kconfig > > @@ -52,9 +52,10 @@ config EVTCHN_FIFO > > > > If unsure, say Y. > > > > -config PDX_COMPRESSION > > - bool "PDX (Page inDeX) compression" if EXPERT && !X86 && !RISCV > > - default ARM || PPC > > ... for x86 (and RISC-V) this option couldn't be selected. Whereas ... > > > @@ -67,6 +68,17 @@ config PDX_COMPRESSION > > If your platform does not have sparse RAM banks, do not enable PDX > > compression. > > > > +config PDX_MASK_COMPRESSION > > + bool "Mask compression" > > + help > > + Compression relying on all RAM addresses sharing a zeroed bit region. > > ... this option is now available, as the prior !X86 && !RISCV doesn't > re-appear here. (As the description mentions it, that dependency clearly > can't appear on the enclosing choice itself.) Since x86 actually still > should have mask compression implemented properly, that's fine (from my > pov; iirc I even asked that it would have remained available when the > earlier change was done), whereas I think for RISC-V it's not quite right > to offer the option. It also did escape me why the option was made > available for PPC, which I'm pretty sure also lacks the logic to determine > a suitable mask. Yes, the only architectures that have functional PDX compression are x86 and ARM, as neither RISC-V nor PowerPC call the initialization functions. AFAICT this is harmless apart from giving the wrong impression to the user that PDX compression might be implemented. Would you prefer for me to introduce a new HAS_PDX config option that's selected by x86 and ARM, and is used to enable the choice PDX config? Thanks, Roger.