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Thu, 27 Mar 2025 06:36:27 -0700 (PDT) Message-ID: <92bcf196-a138-4784-8bfd-c73a1d430321@suse.com> Date: Thu, 27 Mar 2025 14:36:25 +0100 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: Andrew Cooper 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-US From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 27.03.2025 13:53, Andrew Cooper wrote: > 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. Yes indeed. > All of this needs purging from the API/ABIs before RISC-V/PPC inherit > the mistakes that are holding x86 and ARM back. I'm curious to learn how you envision to support a 32-bit guest on RV128, for example. You dislike the compat layer, and you also dislike xen_ulong_t (I agree its name is potentially misleading). So you must be thinking of something entirely new to express in particular interfacing structures. Jan