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Wed, 26 Feb 2025 05:37:53 -0800 (PST) Message-ID: <87289f57-8862-4300-948c-62e05e4de5ff@citrix.com> Date: Wed, 26 Feb 2025 13:37:52 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6/8] x86/IDT: Generate bsp_idt[] at build time To: Jan Beulich Cc: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Xen-devel References: <20250224160509.1117847-1-andrew.cooper3@citrix.com> <20250224160509.1117847-7-andrew.cooper3@citrix.com> <9524c92f-cc5c-480a-935c-f3b51618c03e@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: <9524c92f-cc5c-480a-935c-f3b51618c03e@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 26/02/2025 12:39 pm, Jan Beulich wrote: > On 24.02.2025 17:05, Andrew Cooper wrote: >> --- /dev/null >> +++ b/xen/arch/x86/include/asm/gen-idt.h >> @@ -0,0 +1,121 @@ >> +/* >> + * Generator for IDT entries. >> + * >> + * Caller to provide GEN(vector, symbol, dpl, autogen) macro >> + * >> + * Symbols are 'entry_0xYY' if there is no better name available. Regular >> + * handlers set autogen=1, while manual (autogen=0) require the symbol to be >> + * implemented somewhere else. >> + */ > Doesn't this need something for Eclair to spot the deliberate absence of a > header guard? Eclair doesn't complain, although I'm not entirely sure why. >> +#define DPL0 0 >> +#define DPL1 1 >> +#define DPL3 3 >> + >> +#define manual 0 >> +#define autogen 1 >> + >> +#define GEN16(i) \ >> + GEN(0x ## i ## 0, entry_0x ## i ## 0, DPL0, autogen) \ >> + GEN(0x ## i ## 1, entry_0x ## i ## 1, DPL0, autogen) \ >> + GEN(0x ## i ## 2, entry_0x ## i ## 2, DPL0, autogen) \ >> + GEN(0x ## i ## 3, entry_0x ## i ## 3, DPL0, autogen) \ >> + GEN(0x ## i ## 4, entry_0x ## i ## 4, DPL0, autogen) \ >> + GEN(0x ## i ## 5, entry_0x ## i ## 5, DPL0, autogen) \ >> + GEN(0x ## i ## 6, entry_0x ## i ## 6, DPL0, autogen) \ >> + GEN(0x ## i ## 7, entry_0x ## i ## 7, DPL0, autogen) \ >> + GEN(0x ## i ## 8, entry_0x ## i ## 8, DPL0, autogen) \ >> + GEN(0x ## i ## 9, entry_0x ## i ## 9, DPL0, autogen) \ >> + GEN(0x ## i ## a, entry_0x ## i ## a, DPL0, autogen) \ >> + GEN(0x ## i ## b, entry_0x ## i ## b, DPL0, autogen) \ >> + GEN(0x ## i ## c, entry_0x ## i ## c, DPL0, autogen) \ >> + GEN(0x ## i ## d, entry_0x ## i ## d, DPL0, autogen) \ >> + GEN(0x ## i ## e, entry_0x ## i ## e, DPL0, autogen) \ >> + GEN(0x ## i ## f, entry_0x ## i ## f, DPL0, autogen) >> + >> + >> +GEN(0x00, entry_DE, DPL0, manual) >> +GEN(0x01, entry_DB, DPL0, manual) >> +GEN(0x02, entry_NMI, DPL0, manual) >> +GEN(0x03, entry_BP, DPL3, manual) >> +GEN(0x04, entry_OF, DPL3, manual) > Would this better be > > #ifdef CONFIG_PV32 > GEN(0x04, entry_OF, DPL3, manual) > #else > GEN(0x04, entry_0x04, DPL0, autogen) > #endif > > ? (Not necessarily in this patch, but in principle.) No.  INTO can still be used in compatibility mode segment. Furthermore, for any exception we know about, we want a manual one to avoid the error-code realignment logic where possible. > >> --- /dev/null >> +++ b/xen/arch/x86/include/asm/gen-idt.lds.h >> @@ -0,0 +1,27 @@ >> +/* >> + * Linker file fragment to help format the IDT correctly >> + * >> + * The IDT, having grown compatibly since the 16 bit days, has the entrypoint >> + * address field split into 3. x86 ELF lacks the @lo/@hi/etc relocation forms >> + * commonly found in other architectures for accessing a part of a resolved >> + * symbol address. >> + * >> + * However, the linker can perform the necessary calculations and provide them >> + * under new symbol names. We use this to generate the low and next 16 bits >> + * of the address for each handler. >> + * >> + * The upper 32 bits are always a constant as Xen's .text/data/rodata sits in >> + * a single aligned 1G range, so do not need calculating in this manner. >> + */ >> +#ifndef X86_IDT_GEN_LDS_H >> +#define X86_IDT_GEN_LDS_H >> + >> +#define GEN(vec, sym, dpl, auto) \ >> + PROVIDE_HIDDEN(IDT_ ## sym ## _ADDR1 = ABSOLUTE(((sym) & 0xffff))); \ >> + PROVIDE_HIDDEN(IDT_ ## sym ## _ADDR2 = ABSOLUTE(((sym >> 16) & 0xffff))); > Not sure if Eclair gets to see this at all, but maybe better parenthesize > sym also in the latter instance? Oh, yes. > As to the final semicolon - ideally this would be on the use sites of GEN(), > for things to look more C-ish. Yet I won't insist, as gen-idt.h ends up > looking sufficiently uniform for this to not be a major concern. I'm afraid it's necessary (and too in entry stubs). It's the GEN16() macro, which expands 16x GEN() on the same line. I could drop the GEN16() macro and do everything longhand, but I suspect you'd like that even less. ~Andrew