Re: [PATCH v9 10/19] x86: Secure Launch SMP bringup support

["Jarkko Sakkinen" <jarkko@kernel.org>]

On Fri May 31, 2024 at 4:03 AM EEST, Ross Philipson wrote:
> On Intel, the APs are left in a well documented state after TXT performs
> the late launch. Specifically they cannot have #INIT asserted on them so
> a standard startup via INIT/SIPI/SIPI cannot be performed. Instead the
> early SL stub code uses MONITOR and MWAIT to park the APs. The realmode/init.c
> code updates the jump address for the waiting APs with the location of the
> Secure Launch entry point in the RM piggy after it is loaded and fixed up.
> As the APs are woken up by writing the monitor, the APs jump to the Secure
> Launch entry point in the RM piggy which mimics what the real mode code would
> do then jumps to the standard RM piggy protected mode entry point.
>
> Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
> ---
>  arch/x86/include/asm/realmode.h      |  3 ++
>  arch/x86/kernel/smpboot.c            | 58 +++++++++++++++++++++++++++-
>  arch/x86/realmode/init.c             |  3 ++
>  arch/x86/realmode/rm/header.S        |  3 ++
>  arch/x86/realmode/rm/trampoline_64.S | 32 +++++++++++++++
>  5 files changed, 97 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
> index 87e5482acd0d..339b48e2543d 100644
> --- a/arch/x86/include/asm/realmode.h
> +++ b/arch/x86/include/asm/realmode.h
> @@ -38,6 +38,9 @@ struct real_mode_header {
>  #ifdef CONFIG_X86_64
>  	u32	machine_real_restart_seg;
>  #endif
> +#ifdef CONFIG_SECURE_LAUNCH
> +	u32	sl_trampoline_start32;
> +#endif
>  };
>  
>  /* This must match data at realmode/rm/trampoline_{32,64}.S */
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 0c35207320cb..adb521221d6c 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -60,6 +60,7 @@
>  #include <linux/stackprotector.h>
>  #include <linux/cpuhotplug.h>
>  #include <linux/mc146818rtc.h>
> +#include <linux/slaunch.h>
>  
>  #include <asm/acpi.h>
>  #include <asm/cacheinfo.h>
> @@ -868,6 +869,56 @@ int common_cpu_up(unsigned int cpu, struct task_struct *idle)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_SECURE_LAUNCH
> +
> +static bool slaunch_is_txt_launch(void)
> +{
> +	if ((slaunch_get_flags() & (SL_FLAG_ACTIVE|SL_FLAG_ARCH_TXT)) ==
> +	    (SL_FLAG_ACTIVE | SL_FLAG_ARCH_TXT))
> +		return true;
> +
> +	return false;
> +}

static inline bool slaunch_is_txt_launch(void)
{
	u32 mask =  SL_FLAG_ACTIVE | SL_FLAG_ARCH_TXT;

	return slaunch_get_flags() & mask == mask;
}


> +
> +/*
> + * TXT AP startup is quite different than normal. The APs cannot have #INIT
> + * asserted on them or receive SIPIs. The early Secure Launch code has parked
> + * the APs using monitor/mwait. This will wake the APs by writing the monitor
> + * and have them jump to the protected mode code in the rmpiggy where the rest
> + * of the SMP boot of the AP will proceed normally.
> + */
> +static void slaunch_wakeup_cpu_from_txt(int cpu, int apicid)
> +{
> +	struct sl_ap_wake_info *ap_wake_info;
> +	struct sl_ap_stack_and_monitor *stack_monitor = NULL;

struct sl_ap_stack_and_monitor *stack_monitor; /* note: no initialization */
struct sl_ap_wake_info *ap_wake_info;


> +
> +	ap_wake_info = slaunch_get_ap_wake_info();
> +
> +	stack_monitor = (struct sl_ap_stack_and_monitor *)__va(ap_wake_info->ap_wake_block +
> +							       ap_wake_info->ap_stacks_offset);
> +
> +	for (unsigned int i = TXT_MAX_CPUS - 1; i >= 0; i--) {
> +		if (stack_monitor[i].apicid == apicid) {
> +			/* Write the monitor */

I'd remove this comment.

> +			stack_monitor[i].monitor = 1;
> +			break;
> +		}
> +	}
> +}
> +
> +#else
> +
> +static inline bool slaunch_is_txt_launch(void)
> +{
> +	return false;
> +}
> +
> +static inline void slaunch_wakeup_cpu_from_txt(int cpu, int apicid)
> +{
> +}
> +
> +#endif  /* !CONFIG_SECURE_LAUNCH */
> +
>  /*
>   * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
>   * (ie clustered apic addressing mode), this is a LOGICAL apic ID.
> @@ -877,7 +928,7 @@ int common_cpu_up(unsigned int cpu, struct task_struct *idle)
>  static int do_boot_cpu(u32 apicid, int cpu, struct task_struct *idle)
>  {
>  	unsigned long start_ip = real_mode_header->trampoline_start;
> -	int ret;
> +	int ret = 0;
>  
>  #ifdef CONFIG_X86_64
>  	/* If 64-bit wakeup method exists, use the 64-bit mode trampoline IP */
> @@ -922,12 +973,15 @@ static int do_boot_cpu(u32 apicid, int cpu, struct task_struct *idle)
>  
>  	/*
>  	 * Wake up a CPU in difference cases:
> +	 * - Intel TXT DRTM launch uses its own method to wake the APs
>  	 * - Use a method from the APIC driver if one defined, with wakeup
>  	 *   straight to 64-bit mode preferred over wakeup to RM.
>  	 * Otherwise,
>  	 * - Use an INIT boot APIC message
>  	 */
> -	if (apic->wakeup_secondary_cpu_64)
> +	if (slaunch_is_txt_launch())
> +		slaunch_wakeup_cpu_from_txt(cpu, apicid);
> +	else if (apic->wakeup_secondary_cpu_64)
>  		ret = apic->wakeup_secondary_cpu_64(apicid, start_ip);
>  	else if (apic->wakeup_secondary_cpu)
>  		ret = apic->wakeup_secondary_cpu(apicid, start_ip);
> diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
> index f9bc444a3064..d95776cb30d3 100644
> --- a/arch/x86/realmode/init.c
> +++ b/arch/x86/realmode/init.c
> @@ -4,6 +4,7 @@
>  #include <linux/memblock.h>
>  #include <linux/cc_platform.h>
>  #include <linux/pgtable.h>
> +#include <linux/slaunch.h>
>  
>  #include <asm/set_memory.h>
>  #include <asm/realmode.h>
> @@ -210,6 +211,8 @@ void __init init_real_mode(void)
>  
>  	setup_real_mode();
>  	set_real_mode_permissions();
> +
> +	slaunch_fixup_jump_vector();
>  }
>  
>  static int __init do_init_real_mode(void)
> diff --git a/arch/x86/realmode/rm/header.S b/arch/x86/realmode/rm/header.S
> index 2eb62be6d256..3b5cbcbbfc90 100644
> --- a/arch/x86/realmode/rm/header.S
> +++ b/arch/x86/realmode/rm/header.S
> @@ -37,6 +37,9 @@ SYM_DATA_START(real_mode_header)
>  #ifdef CONFIG_X86_64
>  	.long	__KERNEL32_CS
>  #endif
> +#ifdef CONFIG_SECURE_LAUNCH
> +	.long	pa_sl_trampoline_start32
> +#endif
>  SYM_DATA_END(real_mode_header)
>  
>  	/* End signature, used to verify integrity */
> diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S
> index 14d9c7daf90f..b0ce6205d7ea 100644
> --- a/arch/x86/realmode/rm/trampoline_64.S
> +++ b/arch/x86/realmode/rm/trampoline_64.S
> @@ -122,6 +122,38 @@ SYM_CODE_END(sev_es_trampoline_start)
>  
>  	.section ".text32","ax"
>  	.code32
> +#ifdef CONFIG_SECURE_LAUNCH
> +	.balign 4
> +SYM_CODE_START(sl_trampoline_start32)
> +	/*
> +	 * The early secure launch stub AP wakeup code has taken care of all
> +	 * the vagaries of launching out of TXT. This bit just mimics what the
> +	 * 16b entry code does and jumps off to the real startup_32.
> +	 */
> +	cli
> +	wbinvd
> +
> +	/*
> +	 * The %ebx provided is not terribly useful since it is the physical
> +	 * address of tb_trampoline_start and not the base of the image.
> +	 * Use pa_real_mode_base, which is fixed up, to get a run time
> +	 * base register to use for offsets to location that do not have
> +	 * pa_ symbols.
> +	 */
> +	movl    $pa_real_mode_base, %ebx
> +
> +	LOCK_AND_LOAD_REALMODE_ESP lock_pa=1
> +
> +	lgdt    tr_gdt(%ebx)
> +	lidt    tr_idt(%ebx)
> +
> +	movw	$__KERNEL_DS, %dx	# Data segment descriptor
> +
> +	/* Jump to where the 16b code would have jumped */
> +	ljmpl	$__KERNEL32_CS, $pa_startup_32
> +SYM_CODE_END(sl_trampoline_start32)
> +#endif
> +
>  	.balign 4
>  SYM_CODE_START(startup_32)
>  	movl	%edx, %ss

BR, Jarkko