From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Daniel Kiper <daniel.kiper@oracle.com>, xen-devel@lists.xenproject.org
Cc: jgross@suse.com, sstabellini@kernel.org, cardoe@cardoe.com,
pgnet.dev@gmail.com, ning.sun@intel.com, julien.grall@arm.com,
david.vrabel@citrix.com, jbeulich@suse.com,
qiaowei.ren@intel.com, gang.wei@intel.com, fu.wei@linaro.org
Subject: Re: [PATCH v9 07/13] x86: add multiboot2 protocol support for EFI platforms
Date: Wed, 23 Nov 2016 18:52:27 +0000 [thread overview]
Message-ID: <79d93447-f387-ddcd-1dfa-bba4ae5bbe85@citrix.com> (raw)
In-Reply-To: <1475185362-14198-8-git-send-email-daniel.kiper@oracle.com>
On 29/09/16 22:42, 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>
> ---
> 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 | 260 ++++++++++++++++++++++++++++++++++---
> 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, 346 insertions(+), 23 deletions(-)
>
> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> index d423fd8..0155b32 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 +107,49 @@ multiboot2_header_start:
> gdt_boot_descr:
> .word 6*8-1
> .long sym_phys(trampoline_gdt)
> + .long 0 /* Needed for 64-bit lgdt */
> +
> +cs32_switch_addr:
> + .long sym_phys(cs32_switch)
> + .word BOOT_CS32
> +
> + .align 4
> +vga_text_buffer:
> + .long 0xb8000
Why is this turned into a variable?
>
> .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 +159,182 @@ 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
> +
> + /*
> + * Yes, store that info in skip_realmode variable. I agree that
> + * its name is a bit unfortunate in this context, however, by the
> + * way we disable real mode and other legacy stuff which should
> + * not be run on EFI platforms.
> + */
> + incb skip_realmode(%rip)
Always use add/sub 1 in preference to inc and dec. They are the same
length to encode in 64bit, and avoids a pipeline stall from a merge of
the eflags register.
> + 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,skip_realmode(%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
What is %rax being preserved for?
> + 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. */
> + ljmpl *cs32_switch_addr(%rip)
This would be cleaner and shorter as
push $BOOT_CS32
push $cs32_switch
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 +362,7 @@ __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 +374,33 @@ __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 +416,19 @@ 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 +440,14 @@ 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(skip_realmode)
> + jnz 1f
This should be moved earlier in the BIOS case, rather than inserting
jump. It can go ahead of even the multiboot check, immediately after
loading the gdt.
> +
> + /* Initialize BSS (no nasty surprises!). */
> mov $sym_phys(__bss_start),%edi
> mov $sym_phys(__bss_end),%ecx
> sub %edi,%ecx
> @@ -231,6 +455,7 @@ trampoline_setup:
> shr $2,%ecx
> rep stosl
>
> +1:
> /* Interrogate CPU extended features via CPUID. */
> mov $0x80000000,%eax
> cpuid
> @@ -282,8 +507,13 @@ trampoline_setup:
> cmp $sym_phys(__trampoline_seg_stop),%edi
> jb 1b
>
> + /* Do not parse command line on EFI platform here. */
> + cmpb $0,sym_phys(skip_realmode)
Please don't reuse skip_realmode for something unrelated. For the sake
of one extra byte of data, its not worth the confusion when reading the
code.
~Andrew
> + jnz 1f
> +
> call cmdline_parse_early
>
> +1:
> /* Switch to low-memory stack. */
> mov sym_phys(trampoline_phys),%edi
> lea 0x10000(%edi),%esp
>
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next prev parent reply other threads:[~2016-11-23 18:52 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-29 21:42 [PATCH v9 00/13] x86: multiboot2 protocol support Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 01/13] x86: add " Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 02/13] efi: create efi_enabled() Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 03/13] x86: allow EFI reboot method neither on EFI platforms Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 04/13] x86: properly calculate xen ELF end of image address Daniel Kiper
2016-09-30 9:43 ` Jan Beulich
2016-09-29 21:42 ` [PATCH v9 05/13] efi: build xen.gz with EFI code Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 06/13] efi: create new early memory allocator Daniel Kiper
2016-09-30 9:46 ` Jan Beulich
2016-09-30 10:49 ` Daniel Kiper
2016-10-05 7:02 ` Daniel Kiper
2016-10-05 15:45 ` Julien Grall
2016-10-05 18:30 ` Julien Grall
2016-10-06 12:21 ` Jan Beulich
2016-10-11 13:39 ` Julien Grall
2016-10-12 11:45 ` Jan Beulich
2016-10-12 12:51 ` Julien Grall
2016-10-12 12:59 ` Jan Beulich
2016-10-24 9:03 ` Daniel Kiper
2016-10-24 9:57 ` Jan Beulich
2016-11-03 13:48 ` Daniel Kiper
2016-11-10 10:34 ` Daniel Kiper
2016-10-31 13:32 ` Julien Grall
2016-09-29 21:42 ` [PATCH v9 07/13] x86: add multiboot2 protocol support for EFI platforms Daniel Kiper
2016-11-23 18:52 ` Andrew Cooper [this message]
2016-11-24 11:08 ` Jan Beulich
2016-11-24 21:44 ` Daniel Kiper
2016-11-25 7:50 ` Jan Beulich
2016-11-30 13:45 ` Daniel Kiper
2016-11-30 13:59 ` Jan Beulich
2016-11-30 17:21 ` Daniel Kiper
2016-11-24 21:31 ` Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 08/13] x86/boot: implement early command line parser in C Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 09/13] x86: change default load address from 1 MiB to 2 MiB Daniel Kiper
2016-09-30 10:02 ` Jan Beulich
2016-09-29 21:42 ` [PATCH v9 10/13] x86/setup: use XEN_IMG_OFFSET instead of Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 11/13] x86: make Xen early boot code relocatable Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 12/13] x86/boot: rename sym_phys() to sym_offs() Daniel Kiper
2016-09-29 21:42 ` [PATCH v9 13/13] x86: add multiboot2 protocol support for relocatable images Daniel Kiper
2016-09-30 10:03 ` Jan Beulich
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