Re: [PATCH v11 07/13] x86: add multiboot2 protocol support for EFI platforms

[Doug Goldstein <cardoe@cardoe.com>]

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On 12/5/16 4:25 PM, Daniel Kiper wrote:
> This way Xen can be loaded on EFI platforms using GRUB2 and
> other boot loaders which support multiboot2 protocol.
> 
> Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> ---
> v10 - suggestions/fixes:
>     - replace ljmpl with lretq
>       (suggested by Andrew Cooper),
>     - introduce efi_platform to increase code readability
>       (suggested by Andrew Cooper).
> 
> v9 - suggestions/fixes:
>    - use .L labels instead of numeric ones in multiboot2 data scanning loops
>      (suggested by Jan Beulich).
> 
> v8 - suggestions/fixes:
>    - use __bss_start(%rip)/__bss_end(%rip) instead of
>      of .startof.(.bss)(%rip)/$.sizeof.(.bss) because
>      latter is not tested extensively in different
>      built environments yet
>      (suggested by Andrew Cooper),
>    - fix multiboot2 data scanning loop in x86_32 code
>      (suggested by Jan Beulich),
>    - add check for extra mem for mbi data if Xen is loaded
>      via multiboot2 protocol on EFI platform
>      (suggested by Jan Beulich),
>    - improve comments
>      (suggested by Jan Beulich).
> 
> v7 - suggestions/fixes:
>    - do not allocate twice memory for trampoline if we were
>      loaded via multiboot2 protocol on EFI platform,
>    - wrap long line
>      (suggested by Jan Beulich),
>    - improve comments
>      (suggested by Jan Beulich).
> 
> v6 - suggestions/fixes:
>    - improve label names in assembly
>      error printing code
>      (suggested by Jan Beulich),
>    - improve comments
>      (suggested by Jan Beulich),
>    - various minor cleanups and fixes
>      (suggested by Jan Beulich).
> 
> v4 - suggestions/fixes:
>    - remove redundant BSS alignment,
>    - update BSS alignment check,
>    - use __set_bit() instead of set_bit() if possible
>      (suggested by Jan Beulich),
>    - call efi_arch_cpu() from efi_multiboot2()
>      even if the same work is done later in
>      other place right now
>      (suggested by Jan Beulich),
>    - xen/arch/x86/efi/stub.c:efi_multiboot2()
>      fail properly on EFI platforms,
>    - do not read data beyond the end of multiboot2
>      information in xen/arch/x86/boot/head.S
>      (suggested by Jan Beulich),
>    - use 32-bit registers in x86_64 code if possible
>      (suggested by Jan Beulich),
>    - multiboot2 information address is 64-bit
>      in x86_64 code, so, treat it is as is
>      (suggested by Jan Beulich),
>    - use cmovcc if possible,
>    - leave only one space between rep and stosq
>      (suggested by Jan Beulich),
>    - improve error handling,
>    - improve early error messages,
>      (suggested by Jan Beulich),
>    - improve early error messages printing code,
>    - improve label names
>      (suggested by Jan Beulich),
>    - improve comments
>      (suggested by Jan Beulich),
>    - various minor cleanups.
> 
> v3 - suggestions/fixes:
>    - take into account alignment when skipping multiboot2 fixed part
>      (suggested by Konrad Rzeszutek Wilk),
>    - improve segment registers initialization
>      (suggested by Jan Beulich),
>    - improve comments
>      (suggested by Jan Beulich and Konrad Rzeszutek Wilk),
>    - improve commit message
>      (suggested by Jan Beulich).
> 
> v2 - suggestions/fixes:
>    - generate multiboot2 header using macros
>      (suggested by Jan Beulich),
>    - switch CPU to x86_32 mode before
>      jumping to 32-bit code
>      (suggested by Andrew Cooper),
>    - reduce code changes to increase patch readability
>      (suggested by Jan Beulich),
>    - improve comments
>      (suggested by Jan Beulich),
>    - ignore MULTIBOOT2_TAG_TYPE_BASIC_MEMINFO tag on EFI platform
>      and find on my own multiboot2.mem_lower value,
>    - stop execution if EFI platform is detected
>      in legacy BIOS path.
> ---
>  xen/arch/x86/boot/head.S          |  263 ++++++++++++++++++++++++++++++++++---
>  xen/arch/x86/efi/efi-boot.h       |   54 +++++++-
>  xen/arch/x86/efi/stub.c           |   38 ++++++
>  xen/arch/x86/x86_64/asm-offsets.c |    2 +
>  xen/arch/x86/xen.lds.S            |    4 +-
>  xen/common/efi/boot.c             |   11 ++
>  6 files changed, 349 insertions(+), 23 deletions(-)
> 
> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> index d423fd8..ac93df0 100644
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -89,6 +89,13 @@ multiboot2_header_start:
>                     0, /* Number of the lines - no preference. */ \
>                     0  /* Number of bits per pixel - no preference. */
>  
> +        /* Inhibit bootloader from calling ExitBootServices(). */
> +        mb2ht_init MB2_HT(EFI_BS), MB2_HT(OPTIONAL)
> +
> +        /* EFI64 entry point. */
> +        mb2ht_init MB2_HT(ENTRY_ADDRESS_EFI64), MB2_HT(OPTIONAL), \
> +                   sym_phys(__efi64_start)
> +
>          /* Multiboot2 header end tag. */
>          mb2ht_init MB2_HT(END), MB2_HT(REQUIRED)
>  .Lmultiboot2_header_end:
> @@ -100,20 +107,48 @@ multiboot2_header_start:
>  gdt_boot_descr:
>          .word   6*8-1
>          .long   sym_phys(trampoline_gdt)
> +        .long   0 /* Needed for 64-bit lgdt */
> +
> +        .align 4
> +vga_text_buffer:
> +        .long   0xb8000
> +
> +efi_platform:
> +        .byte   0
>  
>  .Lbad_cpu_msg: .asciz "ERR: Not a 64-bit CPU!"
>  .Lbad_ldr_msg: .asciz "ERR: Not a Multiboot bootloader!"
> +.Lbad_ldr_nbs: .asciz "ERR: Bootloader shutdown EFI x64 boot services!"
> +.Lbad_ldr_nst: .asciz "ERR: EFI SystemTable is not provided by bootloader!"
> +.Lbad_ldr_nih: .asciz "ERR: EFI ImageHandle is not provided by bootloader!"
> +.Lbad_efi_msg: .asciz "ERR: EFI IA-32 platforms are not supported!"
>  
>          .section .init.text, "ax", @progbits
>  
>  bad_cpu:
>          mov     $(sym_phys(.Lbad_cpu_msg)),%esi # Error message
> -        jmp     print_err
> +        jmp     .Lget_vtb
>  not_multiboot:
>          mov     $(sym_phys(.Lbad_ldr_msg)),%esi # Error message
> -print_err:
> -        mov     $0xB8000,%edi  # VGA framebuffer
> -1:      mov     (%esi),%bl
> +        jmp     .Lget_vtb
> +.Lmb2_no_st:
> +        mov     $(sym_phys(.Lbad_ldr_nst)),%esi # Error message
> +        jmp     .Lget_vtb
> +.Lmb2_no_ih:
> +        mov     $(sym_phys(.Lbad_ldr_nih)),%esi # Error message
> +        jmp     .Lget_vtb
> +.Lmb2_no_bs:
> +        mov     $(sym_phys(.Lbad_ldr_nbs)),%esi # Error message
> +        xor     %edi,%edi                       # No VGA text buffer
> +        jmp     .Lsend_chr
> +.Lmb2_efi_ia_32:
> +        mov     $(sym_phys(.Lbad_efi_msg)),%esi # Error message
> +        xor     %edi,%edi                       # No VGA text buffer
> +        jmp     .Lsend_chr
> +.Lget_vtb:
> +        mov     sym_phys(vga_text_buffer),%edi
> +.Lsend_chr:
> +        mov     (%esi),%bl
>          test    %bl,%bl        # Terminate on '\0' sentinel
>          je      .Lhalt
>          mov     $0x3f8+5,%dx   # UART Line Status Register
> @@ -123,13 +158,186 @@ print_err:
>          mov     $0x3f8+0,%dx   # UART Transmit Holding Register
>          mov     %bl,%al
>          out     %al,%dx        # Send a character over the serial line
> -        movsb                  # Write a character to the VGA framebuffer
> +        test    %edi,%edi      # Is the VGA text buffer available?
> +        jz      .Lsend_chr
> +        movsb                  # Write a character to the VGA text buffer
>          mov     $7,%al
> -        stosb                  # Write an attribute to the VGA framebuffer
> -        jmp     1b
> +        stosb                  # Write an attribute to the VGA text buffer
> +        jmp     .Lsend_chr
>  .Lhalt: hlt
>          jmp     .Lhalt
>  
> +        .code64
> +
> +__efi64_start:
> +        cld
> +
> +        /* VGA is not available on EFI platforms. */
> +        movl   $0,vga_text_buffer(%rip)
> +
> +        /* Check for Multiboot2 bootloader. */
> +        cmp     $MULTIBOOT2_BOOTLOADER_MAGIC,%eax
> +        je      .Lefi_multiboot2_proto
> +
> +        /* Jump to not_multiboot after switching CPU to x86_32 mode. */
> +        lea     not_multiboot(%rip),%edi
> +        jmp     x86_32_switch
> +
> +.Lefi_multiboot2_proto:
> +        /* Zero EFI SystemTable and EFI ImageHandle addresses. */
> +        xor     %esi,%esi
> +        xor     %edi,%edi
> +
> +        /* Skip Multiboot2 information fixed part. */
> +        lea     (MB2_fixed_sizeof+MULTIBOOT2_TAG_ALIGN-1)(%rbx),%ecx
> +        and     $~(MULTIBOOT2_TAG_ALIGN-1),%ecx
> +
> +.Lefi_mb2_tsize:
> +        /* Check Multiboot2 information total size. */
> +        mov     %ecx,%r8d
> +        sub     %ebx,%r8d
> +        cmp     %r8d,MB2_fixed_total_size(%rbx)
> +        jbe     run_bs
> +
> +        /* Are EFI boot services available? */
> +        cmpl    $MULTIBOOT2_TAG_TYPE_EFI_BS,MB2_tag_type(%rcx)
> +        jne     .Lefi_mb2_st
> +
> +        /* We are on EFI platform and EFI boot services are available. */
> +        incb    efi_platform(%rip)
> +
> +        /*
> +         * Disable real mode and other legacy stuff which should not
> +         * be run on EFI platforms.
> +         */
> +        incb    skip_realmode(%rip)
> +        jmp     .Lefi_mb2_next_tag
> +
> +.Lefi_mb2_st:
> +        /* Get EFI SystemTable address from Multiboot2 information. */
> +        cmpl    $MULTIBOOT2_TAG_TYPE_EFI64,MB2_tag_type(%rcx)
> +        cmove   MB2_efi64_st(%rcx),%rsi
> +        je      .Lefi_mb2_next_tag
> +
> +        /* Get EFI ImageHandle address from Multiboot2 information. */
> +        cmpl    $MULTIBOOT2_TAG_TYPE_EFI64_IH,MB2_tag_type(%rcx)
> +        cmove   MB2_efi64_ih(%rcx),%rdi
> +        je      .Lefi_mb2_next_tag
> +
> +        /* Is it the end of Multiboot2 information? */
> +        cmpl    $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%rcx)
> +        je      run_bs
> +
> +.Lefi_mb2_next_tag:
> +        /* Go to next Multiboot2 information tag. */
> +        add     MB2_tag_size(%rcx),%ecx
> +        add     $(MULTIBOOT2_TAG_ALIGN-1),%ecx
> +        and     $~(MULTIBOOT2_TAG_ALIGN-1),%ecx
> +        jmp     .Lefi_mb2_tsize
> +
> +run_bs:
> +        /* Are EFI boot services available? */
> +        cmpb    $0,efi_platform(%rip)
> +        jnz     0f
> +
> +        /* Jump to .Lmb2_no_bs after switching CPU to x86_32 mode. */
> +        lea     .Lmb2_no_bs(%rip),%edi
> +        jmp     x86_32_switch
> +
> +0:
> +        /* Is EFI SystemTable address provided by boot loader? */
> +        test    %rsi,%rsi
> +        jnz     1f
> +
> +        /* Jump to .Lmb2_no_st after switching CPU to x86_32 mode. */
> +        lea     .Lmb2_no_st(%rip),%edi
> +        jmp     x86_32_switch
> +
> +1:
> +        /* Is EFI ImageHandle address provided by boot loader? */
> +        test    %rdi,%rdi
> +        jnz     2f
> +
> +        /* Jump to .Lmb2_no_ih after switching CPU to x86_32 mode. */
> +        lea     .Lmb2_no_ih(%rip),%edi
> +        jmp     x86_32_switch
> +
> +2:
> +        push    %rax
> +        push    %rdi
> +
> +        /*
> +         * Initialize BSS (no nasty surprises!).
> +         * It must be done earlier than in BIOS case
> +         * because efi_multiboot2() touches it.
> +         */
> +        lea     __bss_start(%rip),%edi
> +        lea     __bss_end(%rip),%ecx
> +        sub     %edi,%ecx
> +        shr     $3,%ecx
> +        xor     %eax,%eax
> +        rep stosq
> +
> +        pop     %rdi
> +
> +        /*
> +         * efi_multiboot2() is called according to System V AMD64 ABI:
> +         *   - IN: %rdi - EFI ImageHandle, %rsi - EFI SystemTable,
> +         *   - OUT: %rax - highest usable memory address below 1 MiB;
> +         *                 memory above this address is reserved for trampoline;
> +         *                 memory below this address is used as a storage for
> +         *                 mbi struct created in reloc().
> +         *
> +         * MULTIBOOT2_TAG_TYPE_BASIC_MEMINFO tag is not provided
> +         * on EFI platforms. Hence, it could not be used like
> +         * on legacy BIOS platforms.
> +         */
> +        call    efi_multiboot2
> +
> +        /* Convert memory address to bytes/16 and store it in safe place. */
> +        shr     $4,%eax
> +        mov     %eax,%ecx
> +
> +        pop     %rax
> +
> +        /* Jump to trampoline_setup after switching CPU to x86_32 mode. */
> +        lea     trampoline_setup(%rip),%edi
> +
> +x86_32_switch:
> +        cli
> +
> +        /* Initialize GDTR. */
> +        lgdt    gdt_boot_descr(%rip)
> +
> +        /* Reload code selector. */
> +        pushq   $BOOT_CS32
> +        lea     cs32_switch(%rip),%edx
> +        push    %rdx
> +        lretq
> +
> +        .code32
> +
> +cs32_switch:
> +        /* Initialize basic data segments. */
> +        mov     $BOOT_DS,%edx
> +        mov     %edx,%ds
> +        mov     %edx,%es
> +        mov     %edx,%ss
> +        /* %esp is initialized later. */
> +
> +        /* Load null descriptor to unused segment registers. */
> +        xor     %edx,%edx
> +        mov     %edx,%fs
> +        mov     %edx,%gs
> +
> +        /* Disable paging. */
> +        mov     %cr0,%edx
> +        and     $(~X86_CR0_PG),%edx
> +        mov     %edx,%cr0
> +
> +        /* Jump to earlier loaded address. */
> +        jmp     *%edi
> +
>  __start:
>          cld
>          cli
> @@ -157,7 +365,7 @@ __start:
>  
>          /* Not available? BDA value will be fine. */
>          cmovnz  MB_mem_lower(%ebx),%edx
> -        jmp     trampoline_setup
> +        jmp     trampoline_bios_setup
>  
>  .Lmultiboot2_proto:
>          /* Skip Multiboot2 information fixed part. */
> @@ -169,24 +377,33 @@ __start:
>          mov     %ecx,%edi
>          sub     %ebx,%edi
>          cmp     %edi,MB2_fixed_total_size(%ebx)
> -        jbe     trampoline_setup
> +        jbe     trampoline_bios_setup
>  
>          /* Get mem_lower from Multiboot2 information. */
>          cmpl    $MULTIBOOT2_TAG_TYPE_BASIC_MEMINFO,MB2_tag_type(%ecx)
>          cmove   MB2_mem_lower(%ecx),%edx
> -        je      trampoline_setup
> +        je      .Lmb2_next_tag
> +
> +        /* EFI IA-32 platforms are not supported. */
> +        cmpl    $MULTIBOOT2_TAG_TYPE_EFI32,MB2_tag_type(%ecx)
> +        je      .Lmb2_efi_ia_32
> +
> +        /* Bootloader shutdown EFI x64 boot services. */
> +        cmpl    $MULTIBOOT2_TAG_TYPE_EFI64,MB2_tag_type(%ecx)
> +        je      .Lmb2_no_bs
>  
>          /* Is it the end of Multiboot2 information? */
>          cmpl    $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%ecx)
> -        je      trampoline_setup
> +        je      trampoline_bios_setup
>  
> +.Lmb2_next_tag:
>          /* Go to next Multiboot2 information tag. */
>          add     MB2_tag_size(%ecx),%ecx
>          add     $(MULTIBOOT2_TAG_ALIGN-1),%ecx
>          and     $~(MULTIBOOT2_TAG_ALIGN-1),%ecx
>          jmp     .Lmb2_tsize
>  
> -trampoline_setup:
> +trampoline_bios_setup:
>          /* Set up trampoline segment 64k below EBDA */
>          movzwl  0x40e,%ecx          /* EBDA segment */
>          cmp     $0xa000,%ecx        /* sanity check (high) */
> @@ -202,16 +419,19 @@ trampoline_setup:
>           * multiboot structure (if available) and use the smallest.
>           */
>          cmp     $0x100,%edx         /* is the multiboot value too small? */
> -        jb      2f                  /* if so, do not use it */
> +        jb      trampoline_setup    /* if so, do not use it */
>          shl     $10-4,%edx
>          cmp     %ecx,%edx           /* compare with BDA value */
>          cmovb   %edx,%ecx           /* and use the smaller */
>  
> -2:      /* Reserve 64kb for the trampoline */
> +        /* Reserve 64kb for the trampoline. */
>          sub     $0x1000,%ecx
>  
>          /* From arch/x86/smpboot.c: start_eip had better be page-aligned! */
>          xor     %cl, %cl
> +
> +trampoline_setup:
> +        /* Save trampoline address for later use. */
>          shl     $4, %ecx
>          mov     %ecx,sym_phys(trampoline_phys)
>  
> @@ -223,7 +443,14 @@ trampoline_setup:
>          call    reloc
>          mov     %eax,sym_phys(multiboot_ptr)
>  
> -        /* Initialize BSS (no nasty surprises!) */
> +        /*
> +         * Do not zero BSS on EFI platform here.
> +         * It was initialized earlier.
> +         */
> +        cmpb    $0,sym_phys(efi_platform)
> +        jnz     1f
> +
> +        /* Initialize BSS (no nasty surprises!). */
>          mov     $sym_phys(__bss_start),%edi
>          mov     $sym_phys(__bss_end),%ecx
>          sub     %edi,%ecx
> @@ -231,6 +458,7 @@ trampoline_setup:
>          shr     $2,%ecx
>          rep stosl
>  
> +1:
>          /* Interrogate CPU extended features via CPUID. */
>          mov     $0x80000000,%eax
>          cpuid
> @@ -282,8 +510,13 @@ trampoline_setup:
>          cmp     $sym_phys(__trampoline_seg_stop),%edi
>          jb      1b
>  
> +        /* Do not parse command line on EFI platform here. */
> +        cmpb    $0,sym_phys(efi_platform)
> +        jnz     1f
> +
>          call    cmdline_parse_early
>  
> +1:
>          /* Switch to low-memory stack.  */
>          mov     sym_phys(trampoline_phys),%edi
>          lea     0x10000(%edi),%esp
> diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
> index 62c010e..dc857d8 100644
> --- a/xen/arch/x86/efi/efi-boot.h
> +++ b/xen/arch/x86/efi/efi-boot.h
> @@ -146,6 +146,8 @@ static void __init efi_arch_process_memory_map(EFI_SYSTEM_TABLE *SystemTable,
>  {
>      struct e820entry *e;
>      unsigned int i;
> +    /* Check for extra mem for mbi data if Xen is loaded via multiboot2 protocol. */
> +    UINTN extra_mem = efi_enabled(EFI_LOADER) ? 0 : (64 << 10);

Just wondering where the constant came from? And if there should be a
little bit of information about it. To me its just weird to shift 64.

>  
>      /* Populate E820 table and check trampoline area availability. */
>      e = e820map - 1;
> @@ -168,7 +170,8 @@ static void __init efi_arch_process_memory_map(EFI_SYSTEM_TABLE *SystemTable,
>              /* fall through */
>          case EfiConventionalMemory:
>              if ( !trampoline_phys && desc->PhysicalStart + len <= 0x100000 &&
> -                 len >= cfg.size && desc->PhysicalStart + len > cfg.addr )
> +                 len >= cfg.size + extra_mem &&
> +                 desc->PhysicalStart + len > cfg.addr )
>                  cfg.addr = (desc->PhysicalStart + len - cfg.size) & PAGE_MASK;

So this is where the current series blows up and fails on real hardware.
No where in the EFI + MB2 code path is cfg.size ever initialized. Its
only initialized in the straight EFI case. The result is that cfg.addr
is set to the section immediately following this. Took a bit to
trackdown because I checked for memory overlaps with where Xen was
loaded and where it was relocated to but forgot to check for overlaps
with the trampoline code. This is the address where the trampoline jumps
are copied.

Personally I'd like to see an ASSERT added or the code swizzled around
in such a way that its not possible to get into a bad state. But this is
probably another patch series.

>              /* fall through */
>          case EfiLoaderCode:
> @@ -210,12 +213,14 @@ static void *__init efi_arch_allocate_mmap_buffer(UINTN map_size)
>  
>  static void __init efi_arch_pre_exit_boot(void)
>  {
> -    if ( !trampoline_phys )
> -    {
> -        if ( !cfg.addr )
> -            blexit(L"No memory for trampoline");
> +    if ( trampoline_phys )
> +        return;
> +
> +    if ( !cfg.addr )
> +        blexit(L"No memory for trampoline");
> +
> +    if ( efi_enabled(EFI_LOADER) )
>          relocate_trampoline(cfg.addr);
> -    }
>  }
>  
>  static void __init noreturn efi_arch_post_exit_boot(void)
> @@ -653,6 +658,43 @@ static bool_t __init efi_arch_use_config_file(EFI_SYSTEM_TABLE *SystemTable)
>  
>  static void efi_arch_flush_dcache_area(const void *vaddr, UINTN size) { }
>  
> +paddr_t __init efi_multiboot2(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
> +{
> +    EFI_GRAPHICS_OUTPUT_PROTOCOL *gop;
> +    UINTN cols, gop_mode = ~0, rows;
> +
> +    __set_bit(EFI_BOOT, &efi_flags);
> +    __set_bit(EFI_RS, &efi_flags);
> +
> +    efi_init(ImageHandle, SystemTable);
> +
> +    efi_console_set_mode();
> +
> +    if ( StdOut->QueryMode(StdOut, StdOut->Mode->Mode,
> +                           &cols, &rows) == EFI_SUCCESS )
> +        efi_arch_console_init(cols, rows);
> +
> +    gop = efi_get_gop();
> +
> +    if ( gop )
> +        gop_mode = efi_find_gop_mode(gop, 0, 0, 0);
> +
> +    efi_arch_edd();
> +    efi_arch_cpu();
> +
> +    efi_tables();
> +    setup_efi_pci();
> +    efi_variables();

This is probably where you missed the call to "efi_arch_memory_setup();"
that gave me hell above.


> +
> +    if ( gop )
> +        efi_set_gop_mode(gop, gop_mode);
> +
> +    efi_exit_boot(ImageHandle, SystemTable);
> +
> +    /* Return highest usable memory address below 1 MiB. */
> +    return cfg.addr;
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/xen/arch/x86/efi/stub.c b/xen/arch/x86/efi/stub.c
> index 4158124..6ea6aa1 100644
> --- a/xen/arch/x86/efi/stub.c
> +++ b/xen/arch/x86/efi/stub.c
> @@ -3,6 +3,44 @@
>  #include <xen/init.h>
>  #include <xen/lib.h>
>  #include <asm/page.h>
> +#include <asm/efibind.h>
> +#include <efi/efidef.h>
> +#include <efi/eficapsule.h>
> +#include <efi/eficon.h>
> +#include <efi/efidevp.h>
> +#include <efi/efiapi.h>
> +
> +/*
> + * Here we are in EFI stub. EFI calls are not supported due to lack
> + * of relevant functionality in compiler and/or linker.
> + *
> + * efi_multiboot2() is an exception. Please look below for more details.
> + */
> +
> +paddr_t __init noreturn efi_multiboot2(EFI_HANDLE ImageHandle,
> +                                       EFI_SYSTEM_TABLE *SystemTable)
> +{
> +    CHAR16 *err = L"Xen does not have EFI code build in!!!\r\nSystem halted!!!\r\n";
> +    SIMPLE_TEXT_OUTPUT_INTERFACE *StdErr;
> +
> +    StdErr = SystemTable->StdErr ? SystemTable->StdErr : SystemTable->ConOut;
> +
> +    /*
> +     * Print error message and halt the system.
> +     *
> +     * We have to open code MS x64 calling convention
> +     * in assembly because here this convention may
> +     * not be directly supported by C compiler.
> +     */
> +    asm volatile(
> +    "    call %2                      \n"
> +    "0:  hlt                          \n"
> +    "    jmp  0b                      \n"
> +       : "+c" (StdErr), "+d" (err) : "g" (StdErr->OutputString)
> +       : "rax", "r8", "r9", "r10", "r11", "memory");
> +
> +    unreachable();
> +}
>  
>  bool efi_enabled(unsigned int feature)
>  {
> diff --git a/xen/arch/x86/x86_64/asm-offsets.c b/xen/arch/x86/x86_64/asm-offsets.c
> index b437a8f..2a22659 100644
> --- a/xen/arch/x86/x86_64/asm-offsets.c
> +++ b/xen/arch/x86/x86_64/asm-offsets.c
> @@ -175,6 +175,8 @@ void __dummy__(void)
>      OFFSET(MB2_tag_type, multiboot2_tag_t, type);
>      OFFSET(MB2_tag_size, multiboot2_tag_t, size);
>      OFFSET(MB2_mem_lower, multiboot2_tag_basic_meminfo_t, mem_lower);
> +    OFFSET(MB2_efi64_st, multiboot2_tag_efi64_t, pointer);
> +    OFFSET(MB2_efi64_ih, multiboot2_tag_efi64_ih_t, pointer);
>      BLANK();
>  
>      OFFSET(DOMAIN_vm_assist, struct domain, vm_assist);
> diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> index b0b1c9b..e0e2529 100644
> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -331,5 +331,5 @@ ASSERT(IS_ALIGNED(__init_end,   PAGE_SIZE), "__init_end misaligned")
>  
>  ASSERT(IS_ALIGNED(trampoline_start, 4), "trampoline_start misaligned")
>  ASSERT(IS_ALIGNED(trampoline_end,   4), "trampoline_end misaligned")
> -ASSERT(IS_ALIGNED(__bss_start,      4), "__bss_start misaligned")
> -ASSERT(IS_ALIGNED(__bss_end,        4), "__bss_end misaligned")
> +ASSERT(IS_ALIGNED(__bss_start,      8), "__bss_start misaligned")
> +ASSERT(IS_ALIGNED(__bss_end,        8), "__bss_end misaligned")
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index 0a93e61..70ed836 100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -79,6 +79,17 @@ static size_t wstrlen(const CHAR16 * s);
>  static int set_color(u32 mask, int bpp, u8 *pos, u8 *sz);
>  static bool_t match_guid(const EFI_GUID *guid1, const EFI_GUID *guid2);
>  
> +static void efi_init(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable);
> +static void efi_console_set_mode(void);
> +static EFI_GRAPHICS_OUTPUT_PROTOCOL *efi_get_gop(void);
> +static UINTN efi_find_gop_mode(EFI_GRAPHICS_OUTPUT_PROTOCOL *gop,
> +                               UINTN cols, UINTN rows, UINTN depth);
> +static void efi_tables(void);
> +static void setup_efi_pci(void);
> +static void efi_variables(void);
> +static void efi_set_gop_mode(EFI_GRAPHICS_OUTPUT_PROTOCOL *gop, UINTN gop_mode);
> +static void efi_exit_boot(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable);
> +
>  static const EFI_BOOT_SERVICES *__initdata efi_bs;
>  static UINT32 __initdata efi_bs_revision;
>  static EFI_HANDLE __initdata efi_ih;
> 

So as an aside, IMHO this is where the series should end and the next
set of patches should be a follow on.
-- 
Doug Goldstein


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