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Message-ID: <20061118012515.GC4321@in.ibm.com> Date: Fri, 17 Nov 2006 20:25:15 -0500 From: Vivek Goyal <vgoyal@...ibm.com> To: Pavel Machek <pavel@....cz> Cc: linux kernel mailing list <linux-kernel@...r.kernel.org>, Reloc Kernel List <fastboot@...ts.osdl.org>, ebiederm@...ssion.com, akpm@...l.org, ak@...e.de, hpa@...or.com, magnus.damm@...il.com, lwang@...hat.com, dzickus@...hat.com, rjw@...k.pl Subject: Re: [PATCH 12/20] x86_64: wakeup.S Misc cleanup On Sat, Nov 18, 2006 at 01:19:07AM +0100, Pavel Machek wrote: > Hi! > > > o Various cleanups. One of the main purpose of cleanups is that make > > wakeup.S as close as possible to trampoline.S. > > > > o Following are the changes > > - Indentations for comments. > > - Changed the gdt table to compact form and to resemble the > > one in trampoline.S > > - Take the jump to 32bit from real mode using ljmpl. Makes code > > more readable. > > - After enabling long mode, directly take a long jump for 64bit > > mode. No need to take an extra jump to "reach_comaptibility_mode" > > - Stack is not used after real mode. So don't load stack in > > 32 bit mode. > > - No need to enable PGE here. > > - No need to do extra EFER read, anyway we trash the read contents. > > - No need to enable system call (EFER_SCE). Anyway it will be > > enabled when original EFER is restored. > > - No need to set MP, ET, NE, WP, AM bits in cr0. Very soon we will > > reload the original cr0 while restroing the processor state. > > > > Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com> > > Signed-off-by: Vivek Goyal <vgoyal@...ibm.com> > > ACK, minor nitpicks: > > > + /* ??? Why I need the accessed bit set in order for this to work? */ > > Yes, I'd like to know :-). > I don't know. :-( May be it is present because in original code also it is present. I just changed it from 9b00 to 9a00 for __KERNEL32_CS and __KERNEL_CS to mark the entry unaccessed and it works fine for me. Eric, any thoughts on this. ? > > + .quad 0x00cf9b000000ffff # __KERNEL32_CS > > + .quad 0x00af9b000000ffff # __KERNEL_CS > > + .quad 0x00cf93000000ffff # __KERNEL_DS > > Can we get a comment telling us what to keep it in sync with? > Ok. Just added a line mentioning that keep it in sync with trampoline.S Please find attached the revised patch. Thanks Vivek o Various cleanups. One of the main purpose of cleanups is that make wakeup.S as close as possible to trampoline.S. o Following are the changes - Indentations for comments. - Changed the gdt table to compact form and to resemble the one in trampoline.S - Take the jump to 32bit from real mode using ljmpl. Makes code more readable. - After enabling long mode, directly take a long jump for 64bit mode. No need to take an extra jump to "reach_comaptibility_mode" - Stack is not used after real mode. So don't load stack in 32 bit mode. - No need to enable PGE here. - No need to do extra EFER read, anyway we trash the read contents. - No need to enable system call (EFER_SCE). Anyway it will be enabled when original EFER is restored. - No need to set MP, ET, NE, WP, AM bits in cr0. Very soon we will reload the original cr0 while restroing the processor state. Signed-off-by: Vivek Goyal <vgoyal@...ibm.com> --- arch/x86_64/kernel/acpi/wakeup.S | 112 +++++++++++++-------------------------- 1 file changed, 40 insertions(+), 72 deletions(-) diff -puN arch/x86_64/kernel/acpi/wakeup.S~x86_64-wakeup.S-misc-cleanups arch/x86_64/kernel/acpi/wakeup.S --- linux-2.6.19-rc5-git2-reloc/arch/x86_64/kernel/acpi/wakeup.S~x86_64-wakeup.S-misc-cleanups 2006-11-17 00:29:30.000000000 -0500 +++ linux-2.6.19-rc5-git2-reloc-root/arch/x86_64/kernel/acpi/wakeup.S 2006-11-17 10:01:10.000000000 -0500 @@ -30,11 +30,12 @@ wakeup_code: cld # setup data segment movw %cs, %ax - movw %ax, %ds # Make ds:0 point to wakeup_start + movw %ax, %ds # Make ds:0 point to wakeup_start movw %ax, %ss - mov $(wakeup_stack - wakeup_code), %sp # Private stack is needed for ASUS board + # Private stack is needed for ASUS board + mov $(wakeup_stack - wakeup_code), %sp - pushl $0 # Kill any dangerous flags + pushl $0 # Kill any dangerous flags popfl movl real_magic - wakeup_code, %eax @@ -45,7 +46,7 @@ wakeup_code: jz 1f lcall $0xc000,$3 movw %cs, %ax - movw %ax, %ds # Bios might have played with that + movw %ax, %ds # Bios might have played with that movw %ax, %ss 1: @@ -75,9 +76,12 @@ wakeup_code: jmp 1f 1: - .byte 0x66, 0xea # prefix + jmpi-opcode - .long wakeup_32 - __START_KERNEL_map - .word __KERNEL_CS + ljmpl *(wakeup_32_vector - wakeup_code) + + .balign 4 +wakeup_32_vector: + .long wakeup_32 - __START_KERNEL_map + .word __KERNEL32_CS, 0 .code32 wakeup_32: @@ -96,65 +100,50 @@ wakeup_32: jnc bogus_cpu movl %edx,%edi - movw $__KERNEL_DS, %ax - movw %ax, %ds - movw %ax, %es - movw %ax, %fs - movw %ax, %gs + movl $__KERNEL_DS, %eax + movl %eax, %ds - movw $__KERNEL_DS, %ax - movw %ax, %ss - - mov $(wakeup_stack - __START_KERNEL_map), %esp movl saved_magic - __START_KERNEL_map, %eax cmpl $0x9abcdef0, %eax jne bogus_32_magic + movw $0x0e00 + 'i', %ds:(0xb8012) + movb $0xa8, %al ; outb %al, $0x80; + /* * Prepare for entering 64bits mode */ - /* Enable PAE mode and PGE */ + /* Enable PAE */ xorl %eax, %eax btsl $5, %eax - btsl $7, %eax movl %eax, %cr4 /* Setup early boot stage 4 level pagetables */ movl $(wakeup_level4_pgt - __START_KERNEL_map), %eax movl %eax, %cr3 - /* Setup EFER (Extended Feature Enable Register) */ - movl $MSR_EFER, %ecx - rdmsr - /* Fool rdmsr and reset %eax to avoid dependences */ - xorl %eax, %eax /* Enable Long Mode */ + xorl %eax, %eax btsl $_EFER_LME, %eax - /* Enable System Call */ - btsl $_EFER_SCE, %eax - /* No Execute supported? */ + /* No Execute supported? */ btl $20,%edi jnc 1f btsl $_EFER_NX, %eax -1: /* Make changes effective */ +1: movl $MSR_EFER, %ecx + xorl %edx, %edx wrmsr - wbinvd xorl %eax, %eax btsl $31, %eax /* Enable paging and in turn activate Long Mode */ btsl $0, %eax /* Enable protected mode */ - btsl $1, %eax /* Enable MP */ - btsl $4, %eax /* Enable ET */ - btsl $5, %eax /* Enable NE */ - btsl $16, %eax /* Enable WP */ - btsl $18, %eax /* Enable AM */ /* Make changes effective */ movl %eax, %cr0 + /* At this point: CR4.PAE must be 1 CS.L must be 0 @@ -162,11 +151,6 @@ wakeup_32: Next instruction must be a branch This must be on identity-mapped page */ - jmp reach_compatibility_mode -reach_compatibility_mode: - movw $0x0e00 + 'i', %ds:(0xb8012) - movb $0xa8, %al ; outb %al, $0x80; - /* * At this point we're in long mode but in 32bit compatibility mode * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn @@ -174,24 +158,19 @@ reach_compatibility_mode: * the new gdt/idt that has __KERNEL_CS with CS.L = 1. */ - movw $0x0e00 + 'n', %ds:(0xb8014) - movb $0xa9, %al ; outb %al, $0x80 - - /* Load new GDT with the 64bit segment using 32bit descriptor */ - movl $(pGDT32 - __START_KERNEL_map), %eax - lgdt (%eax) - - movl $(wakeup_jumpvector - __START_KERNEL_map), %eax /* Finally jump in 64bit mode */ - ljmp *(%eax) + ljmp *(wakeup_long64_vector - __START_KERNEL_map) -wakeup_jumpvector: - .long wakeup_long64 - __START_KERNEL_map - .word __KERNEL_CS + .balign 4 +wakeup_long64_vector: + .long wakeup_long64 - __START_KERNEL_map + .word __KERNEL_CS, 0 .code64 - /* Hooray, we are in Long 64-bit mode (but still running in low memory) */ + /* Hooray, we are in Long 64-bit mode (but still running in + * low memory) + */ wakeup_long64: /* * We must switch to a new descriptor in kernel space for the GDT @@ -201,6 +180,9 @@ wakeup_long64: */ lgdt cpu_gdt_descr - __START_KERNEL_map + movw $0x0e00 + 'n', %ds:(0xb8014) + movb $0xa9, %al ; outb %al, $0x80 + movw $0x0e00 + 'u', %ds:(0xb8016) nop @@ -227,33 +209,19 @@ wakeup_long64: .align 64 gdta: + /* Good to keep gdt in sync with the one in trampoline.S */ .word 0, 0, 0, 0 # dummy - - .word 0, 0, 0, 0 # unused - - .word 0xFFFF # 4Gb - (0x100000*0x1000 = 4Gb) - .word 0 # base address = 0 - .word 0x9B00 # code read/exec. ??? Why I need 0x9B00 (as opposed to 0x9A00 in order for this to work?) - .word 0x00CF # granularity = 4096, 386 - # (+5th nibble of limit) - - .word 0xFFFF # 4Gb - (0x100000*0x1000 = 4Gb) - .word 0 # base address = 0 - .word 0x9200 # data read/write - .word 0x00CF # granularity = 4096, 386 - # (+5th nibble of limit) -# this is 64bit descriptor for code - .word 0xFFFF - .word 0 - .word 0x9A00 # code read/exec - .word 0x00AF # as above, but it is long mode and with D=0 + /* ??? Why I need the accessed bit set in order for this to work? */ + .quad 0x00cf9b000000ffff # __KERNEL32_CS + .quad 0x00af9b000000ffff # __KERNEL_CS + .quad 0x00cf93000000ffff # __KERNEL_DS idt_48a: .word 0 # idt limit = 0 .word 0, 0 # idt base = 0L gdt_48a: - .word 0x8000 # gdt limit=2048, + .word 0x800 # gdt limit=2048, # 256 GDT entries .word 0, 0 # gdt base (filled in later) @@ -263,7 +231,7 @@ video_mode: .quad 0 video_flags: .quad 0 bogus_real_magic: - movb $0xba,%al ; outb %al,$0x80 + movb $0xba,%al ; outb %al,$0x80 jmp bogus_real_magic bogus_32_magic: _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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