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hv: add fixup to trampline code 

Now, trampline code is used by both AP start and BSP s3 resume.

For s3 resume, ACPI (5.2.10 Firmware ACPI Control Structure (FACS).
table 5-37) defines the real mode address should be set to:
  realmode address = CS(waking_vec >> 4): IP(wakeing_vec & 0x000F)

But not all bootloader (like ABL) follow ACPI definition about the
CS:IP setup before jump to trampline code for S3 resume.

To handle all these cases, a long jmp is issued at very beginning
of trampline code to fixup the CS:IP setup. After the fixup, the
CS is set to: (waking_vect >> 4), the IP is set to: (the_address_
of_next_instruction_of_long_jmp & 0xF). Which is aligned with ACPI
definition.

Another thing is that we can't calculate the fixup CS and IP value.
The reason is related with limitations of real mode (can't get
current ip address without stack). So we calculate the CS and IP
when preparing the trampline code.

Signed-off-by: Zheng Gen <gen.zheng@intel.com>
Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>
Acked-by: Eddie Dong <Eddie.dong@intel.com>
This commit is contained in:
Yin Fengwei 2018-06-07 14:00:51 +08:00 committed by lijinxia
parent f3831cdc80
commit e3346754e1
2 changed files with 74 additions and 6 deletions
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32
hypervisor/arch/x86/cpu.c
View File

@ -606,6 +606,32 @@ int cpu_find_logical_id(uint32_t lapic_id)
return -1;
}
extern uint16_t trampline_fixup_cs[];
extern uint16_t trampline_fixup_ip[];
extern uint32_t trampline_fixup_target;
void prepare_trampline(void)
{
uint64_t val;
/*Copy segment for AP initialization code below 1MB */
memcpy_s(_ld_trampline_start,
(unsigned long)&_ld_trampline_size,
_ld_trampline_load,
(unsigned long)&_ld_trampline_size);
/*
* calculate the fixup CS:IP according to fixup target address
* dynamically.
*
* FIXME:
* the val should be set to runtime address of trampline code
* after trampline relocation is enabled.
*/
val = (uint64_t) &trampline_fixup_target;
trampline_fixup_cs[0] = (uint16_t)(val >> 4) & 0xFFFF;
trampline_fixup_ip[0] = (uint16_t)(val & 0xf);
}
/*
* Start all secondary CPUs.
*/
@ -614,11 +640,7 @@ void start_cpus()
uint32_t timeout;
uint32_t expected_up;
/*Copy segment for AP initialization code below 1MB */
memcpy_s(_ld_trampline_start,
(unsigned long)&_ld_trampline_size,
_ld_trampline_load,
(unsigned long)&_ld_trampline_size);
prepare_trampline();
/* Set flag showing number of CPUs expected to be up to all
* cpus

48
hypervisor/arch/x86/trampline.S
View File

@ -2,6 +2,16 @@
* Copyright (C) 2018 Intel Corporation. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*
* This is entry for AP startup and BSP S3 wakeup
*
* When system jump to trampline_start16, the CPU is in x86 real
* mode with no stack setup. CS:IP points to trampline_start16.
*
* The CPU will be changed to long mode finally with temperay
* page table and gdt in this file. Then jump to different C main
* entry according to whether it's AP startup or BSP S3 resume.
* The real page table and gdt will be setup in C main entry.
*/
#include <spinlock.h>
@ -24,8 +34,44 @@
trampline_start16:
/* Disable local interrupts */
cli
/*
* There are two paths system could come here:
* - AP startup
* Silicon will set AP to real mode and setup CS:IP before
* jmp to trampline_start16. And the IP is always 0 for sure.
* - BSP wakeup from S3
* Some bootloader (like ABL) doesn't guarante IP is set to
* zero before jump to trampline_start16 after system resume
* from S3.
*
* To make trampline code could work with all these cases, a far
* jump is issued here as fixup. It will update the CS:IP according
* to where the trampline code is located.
*
* Here, we issue a far jump with "JMP ptr16:16" format (please refer
* sdm vol2A - JMP instruction description). The jump target is set
* to trampline_fixup_target_addr. From trampline_fixup_target_addr,
* The CS has same value for both AP startup and BSP wakeup from S3.
*
* Because the limitation of real mode (can't access ip register
* directly. So can't setup the trampline_fixup_ip and
* trampline_fixup_cs), we have to update the trampline_fixup_ip
* and trampline_fixup_cs when we preparing the trampline code.
*
* Refer to preparing_trampline() for fixup CS:IP setup
*/
.byte 0xea /* Opcode of "JMP ptr16:16" */
.global trampline_fixup_ip
trampline_fixup_ip:
.word 0 /* "EIP is intruction following JUMP instruction" */
.global trampline_fixup_cs
trampline_fixup_cs:
.word 0 /* CS */
.global trampline_fixup_target
trampline_fixup_target:
mov %cs, %ax
mov %ax, %ds