| Message ID | 6d2a906f3321f4f846ccede25a600a4b85183a38.1689710519.git.sanastasio@raptorengineering.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Early serial on Power | expand |
On 18.07.2023 22:20, Shawn Anastasio wrote: > Update ppc64/head.S to set up an initial boot stack, zero the .bss > section, and jump to C. > > Also refactor the endian fixup trampoline into its own macro, since it > will need to be used in multiple places, including every time we make a > call into firmware (see next commit). Please avoid statements making relative connections between patches or commits. You can't know how many commits will end up between both patches; there's no guarantee any series will be committed all in one go. (In rare cases, where needed for one reason or another, committers may be asked to keep things together.) That said, such statements are much less of a problem if given in the remarks section, which isn't going to be committed. > --- a/xen/arch/ppc/include/asm/config.h > +++ b/xen/arch/ppc/include/asm/config.h > @@ -43,7 +43,7 @@ > > #define SMP_CACHE_BYTES (1 << 6) > > -#define STACK_ORDER 2 > +#define STACK_ORDER 0 From the v3 discussion I thought it would follow that the description gain mention of this change (and the why behind it). Strictly speaking this could be a separate change (at which point stating the "why" would hopefully be an obvious part), but I wouldn't want to go as far as demanding this to be split off. > --- a/xen/arch/ppc/ppc64/head.S > +++ b/xen/arch/ppc/ppc64/head.S > @@ -1,30 +1,28 @@ > /* SPDX-License-Identifier: GPL-2.0-or-later */ > > +#include <asm/asm-defns.h> > + > .section .text.header, "ax", %progbits > > ENTRY(start) > /* > - * Depending on how we were booted, the CPU could be running in either > - * Little Endian or Big Endian mode. The following trampoline from Linux > - * cleverly uses an instruction that encodes to a NOP if the CPU's > - * endianness matches the assumption of the assembler (LE, in our case) > - * or a branch to code that performs the endian switch in the other case. > + * NOTE: argument registers (r3-r9) must be preserved until the C entrypoint > */ > - tdi 0, 0, 0x48 /* Reverse endian of b . + 8 */ > - b . + 44 /* Skip trampoline if endian is good */ > - .long 0xa600607d /* mfmsr r11 */ > - .long 0x01006b69 /* xori r11,r11,1 */ > - .long 0x00004039 /* li r10,0 */ > - .long 0x6401417d /* mtmsrd r10,1 */ > - .long 0x05009f42 /* bcl 20,31,$+4 */ > - .long 0xa602487d /* mflr r10 */ > - .long 0x14004a39 /* addi r10,r10,20 */ > - .long 0xa6035a7d /* mtsrr0 r10 */ > - .long 0xa6037b7d /* mtsrr1 r11 */ > - .long 0x2400004c /* rfid */ > - > - /* Now that the endianness is confirmed, continue */ > -1: b 1b > + FIXUP_ENDIAN > + > + /* set up the TOC pointer */ > + LOAD_IMM32(%r2, .TOC.) > + > + /* set up the initial stack */ > + LOAD_IMM32(%r1, cpu0_boot_stack) Similarly I had hoped that if not a code comment, a sentence in the description would appear regarding the (temporary) non-PIC-ness. Jan
diff --git a/xen/arch/ppc/Makefile b/xen/arch/ppc/Makefile index 98220648af..530fba2121 100644 --- a/xen/arch/ppc/Makefile +++ b/xen/arch/ppc/Makefile @@ -1,5 +1,7 @@ obj-$(CONFIG_PPC64) += ppc64/ +obj-y += setup.o + $(TARGET): $(TARGET)-syms cp -f $< $@ diff --git a/xen/arch/ppc/include/asm/asm-defns.h b/xen/arch/ppc/include/asm/asm-defns.h new file mode 100644 index 0000000000..6ea35f6edb --- /dev/null +++ b/xen/arch/ppc/include/asm/asm-defns.h @@ -0,0 +1,40 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#ifndef _ASM_PPC_ASM_DEFNS_H +#define _ASM_PPC_ASM_DEFNS_H + +/* + * Load a 64-bit immediate value into the specified GPR. + */ +#define LOAD_IMM64(reg, val) \ + lis reg, (val) @highest; \ + ori reg, reg, (val) @higher; \ + rldicr reg, reg, 32, 31; \ + oris reg, reg, (val) @h; \ + ori reg, reg, (val) @l; + +#define LOAD_IMM32(reg, val) \ + lis reg, (val) @h; \ + ori reg, reg, (val) @l; \ + +/* + * Depending on how we were booted, the CPU could be running in either + * Little Endian or Big Endian mode. The following trampoline from Linux + * cleverly uses an instruction that encodes to a NOP if the CPU's + * endianness matches the assumption of the assembler (LE, in our case) + * or a branch to code that performs the endian switch in the other case. + */ +#define FIXUP_ENDIAN \ + tdi 0, 0, 0x48; /* Reverse endian of b . + 8 */ \ + b . + 44; /* Skip trampoline if endian is good */ \ + .long 0xa600607d; /* mfmsr r11 */ \ + .long 0x01006b69; /* xori r11,r11,1 */ \ + .long 0x00004039; /* li r10,0 */ \ + .long 0x6401417d; /* mtmsrd r10,1 */ \ + .long 0x05009f42; /* bcl 20,31,$+4 */ \ + .long 0xa602487d; /* mflr r10 */ \ + .long 0x14004a39; /* addi r10,r10,20 */ \ + .long 0xa6035a7d; /* mtsrr0 r10 */ \ + .long 0xa6037b7d; /* mtsrr1 r11 */ \ + .long 0x2400004c /* rfid */ + +#endif /* _ASM_PPC_ASM_DEFNS_H */ diff --git a/xen/arch/ppc/include/asm/config.h b/xen/arch/ppc/include/asm/config.h index b9a6814f00..01ca5d0803 100644 --- a/xen/arch/ppc/include/asm/config.h +++ b/xen/arch/ppc/include/asm/config.h @@ -43,7 +43,7 @@ #define SMP_CACHE_BYTES (1 << 6) -#define STACK_ORDER 2 +#define STACK_ORDER 0 #define STACK_SIZE (PAGE_SIZE << STACK_ORDER) /* 288 bytes below the stack pointer must be preserved by interrupt handlers */ diff --git a/xen/arch/ppc/ppc64/head.S b/xen/arch/ppc/ppc64/head.S index 2fcefb40d8..17f4a3e19c 100644 --- a/xen/arch/ppc/ppc64/head.S +++ b/xen/arch/ppc/ppc64/head.S @@ -1,30 +1,28 @@ /* SPDX-License-Identifier: GPL-2.0-or-later */ +#include <asm/asm-defns.h> + .section .text.header, "ax", %progbits ENTRY(start) /* - * Depending on how we were booted, the CPU could be running in either - * Little Endian or Big Endian mode. The following trampoline from Linux - * cleverly uses an instruction that encodes to a NOP if the CPU's - * endianness matches the assumption of the assembler (LE, in our case) - * or a branch to code that performs the endian switch in the other case. + * NOTE: argument registers (r3-r9) must be preserved until the C entrypoint */ - tdi 0, 0, 0x48 /* Reverse endian of b . + 8 */ - b . + 44 /* Skip trampoline if endian is good */ - .long 0xa600607d /* mfmsr r11 */ - .long 0x01006b69 /* xori r11,r11,1 */ - .long 0x00004039 /* li r10,0 */ - .long 0x6401417d /* mtmsrd r10,1 */ - .long 0x05009f42 /* bcl 20,31,$+4 */ - .long 0xa602487d /* mflr r10 */ - .long 0x14004a39 /* addi r10,r10,20 */ - .long 0xa6035a7d /* mtsrr0 r10 */ - .long 0xa6037b7d /* mtsrr1 r11 */ - .long 0x2400004c /* rfid */ - - /* Now that the endianness is confirmed, continue */ -1: b 1b + FIXUP_ENDIAN + + /* set up the TOC pointer */ + LOAD_IMM32(%r2, .TOC.) + + /* set up the initial stack */ + LOAD_IMM32(%r1, cpu0_boot_stack) + li %r11, 0 + stdu %r11, -STACK_FRAME_OVERHEAD(%r1) + + /* call the C entrypoint */ + bl start_xen + + /* should never return */ + trap .size start, . - start .type start, %function diff --git a/xen/arch/ppc/setup.c b/xen/arch/ppc/setup.c new file mode 100644 index 0000000000..9e90a6179a --- /dev/null +++ b/xen/arch/ppc/setup.c @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#include <xen/init.h> + +/* Xen stack for bringing up the first CPU. */ +unsigned char __initdata cpu0_boot_stack[STACK_SIZE] __aligned(STACK_SIZE); + +/* Macro to adjust thread priority for hardware multithreading */ +#define HMT_very_low() asm volatile ( "or %r31, %r31, %r31" ) + +void __init noreturn start_xen(unsigned long r3, unsigned long r4, + unsigned long r5, unsigned long r6, + unsigned long r7) +{ + for ( ; ; ) + /* Set current hardware thread to very low priority */ + HMT_very_low(); + + unreachable(); +}
Update ppc64/head.S to set up an initial boot stack, zero the .bss section, and jump to C. Also refactor the endian fixup trampoline into its own macro, since it will need to be used in multiple places, including every time we make a call into firmware (see next commit). Signed-off-by: Shawn Anastasio <sanastasio@raptorengineering.com> --- xen/arch/ppc/Makefile | 2 ++ xen/arch/ppc/include/asm/asm-defns.h | 40 ++++++++++++++++++++++++++++ xen/arch/ppc/include/asm/config.h | 2 +- xen/arch/ppc/ppc64/head.S | 38 +++++++++++++------------- xen/arch/ppc/setup.c | 19 +++++++++++++ 5 files changed, 80 insertions(+), 21 deletions(-) create mode 100644 xen/arch/ppc/include/asm/asm-defns.h create mode 100644 xen/arch/ppc/setup.c