linux-kernel - RE: [PATCH] x86/kernel: remove tboot 1:1 page table creation code

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Date:	Fri, 31 Aug 2012 05:18:45 +0000
From:	"Wei, Gang" <gang.wei@...el.com>
To:	"Zhang, Xiaoyan" <xiaoyan.zhang@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"Cihula, Joseph" <joseph.cihula@...el.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"Wei, Gang" <gang.wei@...el.com>
Subject: RE: [PATCH] x86/kernel: remove tboot 1:1 page table creation code

Acked-by: Gang Wei <gang.wei@...el.com>

> From: Xiaoyan Zhang <xiaoyan.zhang@...el.com>
> 
> For TXT boot, while Linux kernel trys to shutdown/S3/S4/reboot, it need to
> jump back to tboot code and do TXT teardown work. Previously kernel zapped
> all mem page identity mapping (va=pa) after booting, so tboot code mem
> address
> was mapped again with identity mapping. Now kernel didn't zap the identity
> mapping page table, so tboot related code can remove the remapping code
> before
> trapping back now.
> 
> Signed-off-by: Xiaoyan Zhang <xiaoyan.zhang@...el.com>
> ---
>  arch/x86/kernel/tboot.c |   78
+++--------------------------------------------
>  1 files changed, 5 insertions(+), 73 deletions(-)
> 
> diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
> index f84fe00..d4f460f 100644
> --- a/arch/x86/kernel/tboot.c
> +++ b/arch/x86/kernel/tboot.c
> @@ -103,71 +103,13 @@ void __init tboot_probe(void)
>  	pr_debug("tboot_size: 0x%x\n", tboot->tboot_size);
>  }
> 
> -static pgd_t *tboot_pg_dir;
> -static struct mm_struct tboot_mm = {
> -	.mm_rb          = RB_ROOT,
> -	.pgd            = swapper_pg_dir,
> -	.mm_users       = ATOMIC_INIT(2),
> -	.mm_count       = ATOMIC_INIT(1),
> -	.mmap_sem       = __RWSEM_INITIALIZER(init_mm.mmap_sem),
> -	.page_table_lock =
> __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
> -	.mmlist         = LIST_HEAD_INIT(init_mm.mmlist),
> -};
> -
>  static inline void switch_to_tboot_pt(void)
>  {
> -	write_cr3(virt_to_phys(tboot_pg_dir));
> -}
> -
> -static int map_tboot_page(unsigned long vaddr, unsigned long pfn,
> -			  pgprot_t prot)
> -{
> -	pgd_t *pgd;
> -	pud_t *pud;
> -	pmd_t *pmd;
> -	pte_t *pte;
> -
> -	pgd = pgd_offset(&tboot_mm, vaddr);
> -	pud = pud_alloc(&tboot_mm, pgd, vaddr);
> -	if (!pud)
> -		return -1;
> -	pmd = pmd_alloc(&tboot_mm, pud, vaddr);
> -	if (!pmd)
> -		return -1;
> -	pte = pte_alloc_map(&tboot_mm, NULL, pmd, vaddr);
> -	if (!pte)
> -		return -1;
> -	set_pte_at(&tboot_mm, vaddr, pte, pfn_pte(pfn, prot));
> -	pte_unmap(pte);
> -	return 0;
> -}
> -
> -static int map_tboot_pages(unsigned long vaddr, unsigned long start_pfn,
> -			   unsigned long nr)
> -{
> -	/* Reuse the original kernel mapping */
> -	tboot_pg_dir = pgd_alloc(&tboot_mm);
> -	if (!tboot_pg_dir)
> -		return -1;
> -
> -	for (; nr > 0; nr--, vaddr += PAGE_SIZE, start_pfn++) {
> -		if (map_tboot_page(vaddr, start_pfn, PAGE_KERNEL_EXEC))
> -			return -1;
> -	}
> -
> -	return 0;
> -}
> -
> -static void tboot_create_trampoline(void)
> -{
> -	u32 map_base, map_size;
> -
> -	/* Create identity map for tboot shutdown code. */
> -	map_base = PFN_DOWN(tboot->tboot_base);
> -	map_size = PFN_UP(tboot->tboot_size);
> -	if (map_tboot_pages(map_base << PAGE_SHIFT, map_base, map_size))
> -		panic("tboot: Error mapping tboot pages (mfns) @ 0x%x,
0x%x\n",
> -		      map_base, map_size);
> +#ifdef CONFIG_X86_32
> +	load_cr3(initial_page_table);
> +#else
> +	write_cr3(real_mode_header->trampoline_pgd);
> +#endif
>  }
> 
>  #ifdef CONFIG_ACPI_SLEEP
> @@ -225,14 +167,6 @@ void tboot_shutdown(u32 shutdown_type)
>  	if (!tboot_enabled())
>  		return;
> 
> -	/*
> -	 * if we're being called before the 1:1 mapping is set up then just
> -	 * return and let the normal shutdown happen; this should only be
> -	 * due to very early panic()
> -	 */
> -	if (!tboot_pg_dir)
> -		return;
> -
>  	/* if this is S3 then set regions to MAC */
>  	if (shutdown_type == TB_SHUTDOWN_S3)
>  		if (tboot_setup_sleep())
> @@ -343,8 +277,6 @@ static __init int tboot_late_init(void)
>  	if (!tboot_enabled())
>  		return 0;
> 
> -	tboot_create_trampoline();
> -
>  	atomic_set(&ap_wfs_count, 0);
>  	register_hotcpu_notifier(&tboot_cpu_notifier);
> 
> --
> 1.7.7.6


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