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Smith" , =?UTF-8?Q?Marek_Marczykowski-G=C3=B3recki?= References: <20240924102811.86884-1-frediano.ziglio@cloud.com> <20240924102811.86884-4-frediano.ziglio@cloud.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: <20240924102811.86884-4-frediano.ziglio@cloud.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 24/09/2024 11:28 am, Frediano Ziglio wrote: > diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S > index 80bba6ff21..6d8eec554b 100644 > --- a/xen/arch/x86/boot/head.S > +++ b/xen/arch/x86/boot/head.S > @@ -253,36 +244,30 @@ __efi64_mb2_start: > shr $3, %ecx > xor %eax, %eax > rep stosq > - mov %edx, %eax > > - /* Check for Multiboot2 bootloader. */ > - cmp $MULTIBOOT2_BOOTLOADER_MAGIC,%eax > - je .Lefi_multiboot2_proto > - > - /* Jump to .Lnot_multiboot after switching CPU to x86_32 mode. */ > - lea .Lnot_multiboot(%rip), %r15 > - jmp x86_32_switch > + /* Save Multiboot2 magic on the stack. */ > + push %rdx > > -.Lefi_multiboot2_proto: > - /* Zero EFI SystemTable, EFI ImageHandle addresses and cmdline. */ > - xor %esi,%esi > - xor %edi,%edi > - xor %edx,%edx > + /* Save Multiboot2 pointer on the stack, keep the stack aligned. */ > + push %rbx I'd merge these two pushes, so     /* Spill MB2 magic.  Spill the pointer too, to keep the stack aligned. */     push %rdx     push %rbx and ... > > - /* Skip Multiboot2 information fixed part. */ > - lea (MB2_fixed_sizeof+MULTIBOOT2_TAG_ALIGN-1)(%rbx),%ecx > - and $~(MULTIBOOT2_TAG_ALIGN-1),%ecx > + /* > + * efi_parse_mbi2() is called according to System V AMD64 ABI: > + * - IN: %edi - Multiboot2 magic, %rsi - Multiboot2 pointer. %rsi below %edi please, for readability. > + * - OUT: %rax - error string. > + */ > + mov %edx, %edi > + mov %rbx, %rsi > + call efi_parse_mbi2 > + lea .Ldirect_error(%rip), %r15 > + test %rax, %rax > + jnz x86_32_switch > > -.Lefi_mb2_tsize: > - /* Check Multiboot2 information total size. */ > - mov %ecx,%r8d > - sub %ebx,%r8d > - cmp %r8d,MB2_fixed_total_size(%rbx) > - jbe .Lrun_bs > + /* Restore Multiboot2 pointer. */ > + pop %rbx > > - /* Are EFI boot services available? */ > - cmpl $MULTIBOOT2_TAG_TYPE_EFI_BS,MB2_tag_type(%rcx) > - jne .Lefi_mb2_st > + /* Restore Multiboot2 magic. */ > + pop %rax ... merge these pops too.  (It's a shame the pushes/pops implement a %edx -> %eax swap for magic, but it's for BSS clearing purposes.) > diff --git a/xen/arch/x86/efi/parse-mbi2.c b/xen/arch/x86/efi/parse-mbi2.c > new file mode 100644 > index 0000000000..6038f35b16 > --- /dev/null > +++ b/xen/arch/x86/efi/parse-mbi2.c > @@ -0,0 +1,58 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +void __init efi_multiboot2(EFI_HANDLE ImageHandle, > + EFI_SYSTEM_TABLE *SystemTable, > + const char *cmdline); This wants to be in a header file seen by all references.  I see you you've fixed up an error in the stub clearly caused by the absence of a shared header. > + > +const char * asmlinkage __init > +efi_parse_mbi2(uint32_t magic, const multiboot2_fixed_t *mbi) > +{ > + const multiboot2_tag_t *tag; > + EFI_HANDLE ImageHandle = NULL; > + EFI_SYSTEM_TABLE *SystemTable = NULL; > + const char *cmdline = NULL; > + bool have_bs = false; > + > + if ( magic != MULTIBOOT2_BOOTLOADER_MAGIC ) > + return "ERR: Not a Multiboot2 bootloader!"; > + > + /* Skip Multiboot2 information fixed part. */ > + tag = _p(ROUNDUP((unsigned long)(mbi + 1), MULTIBOOT2_TAG_ALIGN)); > + > + for ( ; (const void *)tag - (const void *)mbi < mbi->total_size > + && tag->type != MULTIBOOT2_TAG_TYPE_END; > + tag = _p(ROUNDUP((unsigned long)((const void *)tag + tag->size), > + MULTIBOOT2_TAG_ALIGN)) ) > + { > + if ( tag->type == MULTIBOOT2_TAG_TYPE_EFI_BS ) > + have_bs = true; > + else if ( tag->type == MULTIBOOT2_TAG_TYPE_EFI64 ) > + SystemTable = _p(((const multiboot2_tag_efi64_t *)tag)->pointer); > + else if ( tag->type == MULTIBOOT2_TAG_TYPE_EFI64_IH ) > + ImageHandle = _p(((const multiboot2_tag_efi64_ih_t *)tag)->pointer); > + else if ( tag->type == MULTIBOOT2_TAG_TYPE_CMDLINE ) > + cmdline = ((const multiboot2_tag_string_t *)tag)->string; switch ( tag->type ) please.  It's more lines, but more legible. Otherwise, LGTM.  Definitely nice to move this out of asm. ~Andrew