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Thu, 27 Mar 2025 05:53:30 -0700 (PDT) Message-ID: Date: Thu, 27 Mar 2025 12:53:28 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] xen/config.h: Move BITS_PER_* definitions from asm/config.h to xen/config.h To: Jan Beulich Cc: Stefano Stabellini , Julien Grall , Bertrand Marquis , Michal Orzel , Volodymyr Babchuk , Anthony PERARD , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Shawn Anastasio , Alistair Francis , Bob Eshleman , Connor Davis , Oleksii Kurochko , xen-devel@lists.xenproject.org References: <4f085bcbf5b6f1bc42824bfb08724e8a9bbd4918.1743005389.git.oleksii.kurochko@gmail.com> <17a808cf-e676-4c30-9068-34a9a4d568d7@citrix.com> <994b9d44-f82f-4eb7-8742-9041ba2caf17@suse.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; keydata= xsFNBFLhNn8BEADVhE+Hb8i0GV6mihnnr/uiQQdPF8kUoFzCOPXkf7jQ5sLYeJa0cQi6Penp VtiFYznTairnVsN5J+ujSTIb+OlMSJUWV4opS7WVNnxHbFTPYZVQ3erv7NKc2iVizCRZ2Kxn srM1oPXWRic8BIAdYOKOloF2300SL/bIpeD+x7h3w9B/qez7nOin5NzkxgFoaUeIal12pXSR Q354FKFoy6Vh96gc4VRqte3jw8mPuJQpfws+Pb+swvSf/i1q1+1I4jsRQQh2m6OTADHIqg2E ofTYAEh7R5HfPx0EXoEDMdRjOeKn8+vvkAwhviWXTHlG3R1QkbE5M/oywnZ83udJmi+lxjJ5 YhQ5IzomvJ16H0Bq+TLyVLO/VRksp1VR9HxCzItLNCS8PdpYYz5TC204ViycobYU65WMpzWe LFAGn8jSS25XIpqv0Y9k87dLbctKKA14Ifw2kq5OIVu2FuX+3i446JOa2vpCI9GcjCzi3oHV e00bzYiHMIl0FICrNJU0Kjho8pdo0m2uxkn6SYEpogAy9pnatUlO+erL4LqFUO7GXSdBRbw5 gNt25XTLdSFuZtMxkY3tq8MFss5QnjhehCVPEpE6y9ZjI4XB8ad1G4oBHVGK5LMsvg22PfMJ ISWFSHoF/B5+lHkCKWkFxZ0gZn33ju5n6/FOdEx4B8cMJt+cWwARAQABzSlBbmRyZXcgQ29v cGVyIDxhbmRyZXcuY29vcGVyM0BjaXRyaXguY29tPsLBegQTAQgAJAIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUCWKD95wIZAQAKCRBlw/kGpdefoHbdD/9AIoR3k6fKl+RFiFpyAhvO 59ttDFI7nIAnlYngev2XUR3acFElJATHSDO0ju+hqWqAb8kVijXLops0gOfqt3VPZq9cuHlh IMDquatGLzAadfFx2eQYIYT+FYuMoPZy/aTUazmJIDVxP7L383grjIkn+7tAv+qeDfE+txL4 SAm1UHNvmdfgL2/lcmL3xRh7sub3nJilM93RWX1Pe5LBSDXO45uzCGEdst6uSlzYR/MEr+5Z JQQ32JV64zwvf/aKaagSQSQMYNX9JFgfZ3TKWC1KJQbX5ssoX/5hNLqxMcZV3TN7kU8I3kjK mPec9+1nECOjjJSO/h4P0sBZyIUGfguwzhEeGf4sMCuSEM4xjCnwiBwftR17sr0spYcOpqET ZGcAmyYcNjy6CYadNCnfR40vhhWuCfNCBzWnUW0lFoo12wb0YnzoOLjvfD6OL3JjIUJNOmJy RCsJ5IA/Iz33RhSVRmROu+TztwuThClw63g7+hoyewv7BemKyuU6FTVhjjW+XUWmS/FzknSi dAG+insr0746cTPpSkGl3KAXeWDGJzve7/SBBfyznWCMGaf8E2P1oOdIZRxHgWj0zNr1+ooF /PzgLPiCI4OMUttTlEKChgbUTQ+5o0P080JojqfXwbPAyumbaYcQNiH1/xYbJdOFSiBv9rpt TQTBLzDKXok86M7BTQRS4TZ/ARAAkgqudHsp+hd82UVkvgnlqZjzz2vyrYfz7bkPtXaGb9H4 Rfo7mQsEQavEBdWWjbga6eMnDqtu+FC+qeTGYebToxEyp2lKDSoAsvt8w82tIlP/EbmRbDVn 7bhjBlfRcFjVYw8uVDPptT0TV47vpoCVkTwcyb6OltJrvg/QzV9f07DJswuda1JH3/qvYu0p vjPnYvCq4NsqY2XSdAJ02HrdYPFtNyPEntu1n1KK+gJrstjtw7KsZ4ygXYrsm/oCBiVW/OgU g/XIlGErkrxe4vQvJyVwg6YH653YTX5hLLUEL1NS4TCo47RP+wi6y+TnuAL36UtK/uFyEuPy wwrDVcC4cIFhYSfsO0BumEI65yu7a8aHbGfq2lW251UcoU48Z27ZUUZd2Dr6O/n8poQHbaTd 6bJJSjzGGHZVbRP9UQ3lkmkmc0+XCHmj5WhwNNYjgbbmML7y0fsJT5RgvefAIFfHBg7fTY/i kBEimoUsTEQz+N4hbKwo1hULfVxDJStE4sbPhjbsPCrlXf6W9CxSyQ0qmZ2bXsLQYRj2xqd1 bpA+1o1j2N4/au1R/uSiUFjewJdT/LX1EklKDcQwpk06Af/N7VZtSfEJeRV04unbsKVXWZAk uAJyDDKN99ziC0Wz5kcPyVD1HNf8bgaqGDzrv3TfYjwqayRFcMf7xJaL9xXedMcAEQEAAcLB XwQYAQgACQUCUuE2fwIbDAAKCRBlw/kGpdefoG4XEACD1Qf/er8EA7g23HMxYWd3FXHThrVQ HgiGdk5Yh632vjOm9L4sd/GCEACVQKjsu98e8o3ysitFlznEns5EAAXEbITrgKWXDDUWGYxd pnjj2u+GkVdsOAGk0kxczX6s+VRBhpbBI2PWnOsRJgU2n10PZ3mZD4Xu9kU2IXYmuW+e5KCA vTArRUdCrAtIa1k01sPipPPw6dfxx2e5asy21YOytzxuWFfJTGnVxZZSCyLUO83sh6OZhJkk b9rxL9wPmpN/t2IPaEKoAc0FTQZS36wAMOXkBh24PQ9gaLJvfPKpNzGD8XWR5HHF0NLIJhgg 4ZlEXQ2fVp3XrtocHqhu4UZR4koCijgB8sB7Tb0GCpwK+C4UePdFLfhKyRdSXuvY3AHJd4CP 4JzW0Bzq/WXY3XMOzUTYApGQpnUpdOmuQSfpV9MQO+/jo7r6yPbxT7CwRS5dcQPzUiuHLK9i nvjREdh84qycnx0/6dDroYhp0DFv4udxuAvt1h4wGwTPRQZerSm4xaYegEFusyhbZrI0U9tJ B8WrhBLXDiYlyJT6zOV2yZFuW47VrLsjYnHwn27hmxTC/7tvG3euCklmkn9Sl9IAKFu29RSo d5bD8kMSCYsTqtTfT6W4A3qHGvIDta3ptLYpIAOD2sY3GYq2nf3Bbzx81wZK14JdDDHUX2Rs 6+ahAA== In-Reply-To: <994b9d44-f82f-4eb7-8742-9041ba2caf17@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 27/03/2025 8:21 am, Jan Beulich wrote: > On 27.03.2025 01:44, Andrew Cooper wrote: >> On 26/03/2025 5:47 pm, Oleksii Kurochko wrote: >>> diff --git a/xen/include/xen/config.h b/xen/include/xen/config.h >>> index d888b2314d..dbbf2fce62 100644 >>> --- a/xen/include/xen/config.h >>> +++ b/xen/include/xen/config.h >>> @@ -98,4 +98,13 @@ >>> #define ZERO_BLOCK_PTR ((void *)-1L) >>> #endif >>> >>> +#define BYTES_PER_LONG __SIZEOF_LONG__ >>> + >>> +#define BITS_PER_BYTE __CHAR_BIT__ >>> +#define BITS_PER_INT (__SIZEOF_INT__ << 3) >>> +#define BITS_PER_LONG (BYTES_PER_LONG << 3) >>> +#define BITS_PER_LLONG (__SIZEOF_LONG_LONG__ << 3) >>> + >>> +#define POINTER_ALIGN __SIZEOF_POINTER__ >> See how much nicer this is.  This patch possibly wants to wait until >> I've fixed the compiler checks to update to the new baseline, or we can >> just say that staging is staging and corner case error messages are fine. >> >> One thing, you have to replace the "<< 3" as you're hard-coding 8 here >> and ignoring __CHAR_BIT__. >> >> I'd suggest keeping the BITS_PER_BYTE on the LHS, e.g: >> >> #define BITS_PER_INT    (BITS_PER_BYTE * __SIZEOF_INT__) >> >> which tabulates better. >> >> I suggest keeping BITS_PER_XEN_ULONG to be arch-local. > I agree here despite ... > >>   ARM is the >> odd-one-out having a non-64bit arch use a 64bit XEN_ULONG. > ... not agreeing here: x86 is the odd-one-out; I sincerely hope any new ports > to 32-bit architectures / flavors will avoid compat layer translation by making > this type a proper 64-bit one. Architectures truly being 32-bit only, with no > expectation of a 64-bit flavor ever appearing, would be different. I have some very firm opinions about this. It is an error that the type xen_ulong exists, anywhere.  The fact it wasn't named guest_ulong shows a profound misunderstanding of its purpose and usage in the API/ABI. Similarly, BITS_PER_XEN_ULONG is buggily named, and should be BITS_PER_GUEST_ULONG, as demonstrated by it's singular use in Xen (calculating BITS_PER_EVTCHN_WORD(d)). ARM declaring that arm32 uses 64-bit xen_ulongs was cutting a corner that's going to bite twice as hard when 128bit comes along, and RISCV-128 is in progress already. All of this needs purging from the API/ABIs before RISC-V/PPC inherit the mistakes that are holding x86 and ARM back. ~Andrew