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From: Stefano Stabellini <sstabellini@kernel.org>
To: Julien Grall <julien.grall@arm.com>
Cc: xen-devel@lists.xenproject.org,
	Stefano Stabellini <sstabellini@kernel.org>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [Xen-devel] [PATCH v3 13/28] xen/arm32: head: Introduce distinct paths for the boot CPU and secondary CPUs
Date: Thu, 22 Aug 2019 10:11:18 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.21.1908221011090.22783@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <20190812173019.11956-14-julien.grall@arm.com>

On Mon, 12 Aug 2019, Julien Grall wrote:
> The boot code is currently quite difficult to go through because of the
> lack of documentation and a number of indirection to avoid executing
> some path in either the boot CPU or secondary CPUs.
> 
> In an attempt to make the boot code easier to follow, each parts of the
> boot are now in separate functions. Furthermore, the paths for the boot
> CPU and secondary CPUs are now distinct and for now will call each
> functions.
> 
> Follow-ups will remove unnecessary calls and do further improvement
> (such as adding documentation and reshuffling).
> 
> Note that the switch from using the ID mapping to the runtime mapping
> is duplicated for each path. This is because in the future we will need
> to stay longer in the ID mapping for the boot CPU.
> 
> Lastly, it is now required to save lr in cpu_init() becauswe the
> function will call other functions and therefore clobber lr.
> 
> Signed-off-by: Julien Grall <julien.grall@arm.com>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
>     Changes in v3:
>         - Remove hard tab
>         - s/ID map/1:1 mapping/
> 
>     Changes in v2:
>         - Patch added
> ---
>  xen/arch/arm/arm32/head.S | 65 +++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 54 insertions(+), 11 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index c4ee06ba93..4285f76463 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -148,7 +148,19 @@ past_zImage:
>  
>          mov   r12, #0                /* r12 := is_secondary_cpu */
>  
> -        b     common_start
> +        bl    check_cpu_mode
> +        bl    zero_bss
> +        bl    cpu_init
> +        bl    create_page_tables
> +        bl    enable_mmu
> +
> +        /* We are still in the 1:1 mapping. Jump to the runtime Virtual Address. */
> +        ldr   r0, =primary_switched
> +        mov   pc, r0
> +primary_switched:
> +        bl    setup_fixmap
> +        b     launch
> +ENDPROC(start)
>  
>  GLOBAL(init_secondary)
>          cpsid aif                    /* Disable all interrupts */
> @@ -179,8 +191,22 @@ GLOBAL(init_secondary)
>          print_reg r7
>          PRINT(" booting -\r\n")
>  #endif
> -
> -common_start:
> +        bl    check_cpu_mode
> +        bl    zero_bss
> +        bl    cpu_init
> +        bl    create_page_tables
> +        bl    enable_mmu
> +
> +
> +        /* We are still in the 1:1 mapping. Jump to the runtime Virtual Address. */
> +        ldr   r0, =secondary_switched
> +        mov   pc, r0
> +secondary_switched:
> +        bl    setup_fixmap
> +        b     launch
> +ENDPROC(init_secondary)
> +
> +check_cpu_mode:
>          /* Check that this CPU has Hyp mode */
>          mrc   CP32(r0, ID_PFR1)
>          and   r0, r0, #0xf000        /* Bits 12-15 define virt extensions */
> @@ -202,7 +228,10 @@ common_start:
>          b     fail
>  
>  hyp:    PRINT("- Xen starting in Hyp mode -\r\n")
> +        mov   pc, lr
> +ENDPROC(check_cpu_mode)
>  
> +zero_bss:
>          /* Zero BSS On the boot CPU to avoid nasty surprises */
>          teq   r12, #0
>          bne   skip_bss
> @@ -219,8 +248,14 @@ hyp:    PRINT("- Xen starting in Hyp mode -\r\n")
>          blo   1b
>  
>  skip_bss:
> +        mov   pc, lr
> +ENDPROC(zero_bss)
> +
> +cpu_init:
>          PRINT("- Setting up control registers -\r\n")
>  
> +        mov   r5, lr                       /* r5 := return address */
> +
>          /* Get processor specific proc info into r1 */
>          bl    __lookup_processor_type
>          teq   r1, #0
> @@ -231,7 +266,6 @@ skip_bss:
>          PRINT(" -\r\n")
>          b     fail
>  1:
> -
>          /* Jump to cpu_init */
>          ldr   r1, [r1, #PROCINFO_cpu_init]  /* r1 := vaddr(init func) */
>          adr   lr, cpu_init_done             /* Save return address */
> @@ -256,6 +290,10 @@ cpu_init_done:
>          ldr   r0, =HSCTLR_SET
>          mcr   CP32(r0, HSCTLR)
>  
> +        mov   pc, r5                        /* Return address is in r5 */
> +ENDPROC(cpu_init)
> +
> +create_page_tables:
>          /*
>           * Rebuild the boot pagetable's first-level entries. The structure
>           * is described in mm.c.
> @@ -359,15 +397,16 @@ cpu_init_done:
>          /* boot pagetable setup complete */
>  
>          cmp   r6, #1                /* Did we manage to create an identity mapping ? */
> -        beq   1f
> +        moveq pc, lr
>          PRINT("Unable to build boot page tables - Failed to identity map Xen.\r\n")
>          b     fail
>  virtphys_clash:
>          /* Identity map clashes with boot_third, which we cannot handle yet */
>          PRINT("- Unable to build boot page tables - virt and phys addresses clash. -\r\n")
>          b     fail
> +ENDPROC(create_page_tables)
>  
> -1:
> +enable_mmu:
>          PRINT("- Turning on paging -\r\n")
>  
>          /*
> @@ -377,16 +416,16 @@ virtphys_clash:
>          mcr   CP32(r0, TLBIALLH)     /* Flush hypervisor TLBs */
>          dsb   nsh
>  
> -        ldr   r1, =paging            /* Explicit vaddr, not RIP-relative */
>          mrc   CP32(r0, HSCTLR)
>          /* Enable MMU and D-cache */
>          orr   r0, r0, #(SCTLR_Axx_ELx_M|SCTLR_Axx_ELx_C)
>          dsb                          /* Flush PTE writes and finish reads */
>          mcr   CP32(r0, HSCTLR)       /* now paging is enabled */
>          isb                          /* Now, flush the icache */
> -        mov   pc, r1                 /* Get a proper vaddr into PC */
> -paging:
> +        mov   pc, lr
> +ENDPROC(enable_mmu)
>  
> +setup_fixmap:
>          /*
>           * Now we can install the fixmap and dtb mappings, since we
>           * don't need the 1:1 map any more
> @@ -436,12 +475,15 @@ paging:
>          mcr   CP32(r0, TLBIALLH)     /* Flush hypervisor TLB */
>          dsb                          /* Ensure completion of TLB flush */
>          isb
> +        mov   pc, lr
> +ENDPROC(setup_fixmap)
>  
> +launch:
>          PRINT("- Ready -\r\n")
>  
>          /* The boot CPU should go straight into C now */
>          teq   r12, #0
> -        beq   launch
> +        beq   1f
>  
>          /*
>           * Non-boot CPUs need to move on to the proper pagetables, which were
> @@ -460,7 +502,7 @@ paging:
>          dsb                          /* Ensure completion of TLB+BP flush */
>          isb
>  
> -launch:
> +1:
>          ldr   r0, =init_data
>          add   r0, #INITINFO_stack    /* Find the boot-time stack */
>          ldr   sp, [r0]
> @@ -471,6 +513,7 @@ launch:
>          moveq r1, r8                 /*               - DTB address */
>          beq   start_xen              /* and disappear into the land of C */
>          b     start_secondary        /* (to the appropriate entry point) */
> +ENDPROC(launch)
>  
>  /* Fail-stop */
>  fail:   PRINT("- Boot failed -\r\n")
> -- 
> 2.11.0
> 

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  reply	other threads:[~2019-08-22 17:11 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-12 17:29 [Xen-devel] [PATCH v3 00/28] xen/arm: Rework head.S to make it more compliant with the Arm Arm Julien Grall
2019-08-12 17:29 ` [Xen-devel] [PATCH v3 01/28] xen/arm: lpae: Allow more LPAE helpers to be used in assembly Julien Grall
2019-08-22 17:07   ` Stefano Stabellini
2019-08-12 17:29 ` [Xen-devel] [PATCH v3 02/28] xen/arm64: head: Remove 1:1 mapping as soon as it is not used Julien Grall
2019-08-22 17:58   ` Stefano Stabellini
2019-08-22 18:25     ` Julien Grall
2019-08-22 18:29       ` Stefano Stabellini
2019-08-12 17:29 ` [Xen-devel] [PATCH v3 03/28] xen/arm64: head: Rework and document setup_fixmap() Julien Grall
2019-08-12 17:29 ` [Xen-devel] [PATCH v3 04/28] xen/arm64: head: Rework and document launch() Julien Grall
2019-08-12 17:29 ` [Xen-devel] [PATCH v3 05/28] xen/arm64: head: Setup TTBR_EL2 in enable_mmu() and add missing isb Julien Grall
2019-08-12 17:29 ` [Xen-devel] [PATCH v3 06/28] xen/arm64: head: Introduce a macro to get a PC-relative address of a symbol Julien Grall
2019-08-12 17:29 ` [Xen-devel] [PATCH v3 07/28] xen/arm64: head: Fix typo in the documentation on top of init_uart() Julien Grall
2019-08-22 17:08   ` Stefano Stabellini
2019-08-12 17:29 ` [Xen-devel] [PATCH v3 08/28] xen/arm32: head: Add a macro to move an immediate constant into a 32-bit register Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 09/28] xen/arm32: head: Mark the end of subroutines with ENDPROC Julien Grall
2019-08-12 17:33   ` Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 10/28] xen/arm32: head: Don't clobber r14/lr in the macro PRINT Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 11/28] xen/arm32: head: Rework UART initialization on boot CPU Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 12/28] xen/arm32: head: Introduce print_reg Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 13/28] xen/arm32: head: Introduce distinct paths for the boot CPU and secondary CPUs Julien Grall
2019-08-22 17:11   ` Stefano Stabellini [this message]
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 14/28] xen/arm32: head: Rework and document check_cpu_mode() Julien Grall
2019-08-22 17:14   ` Stefano Stabellini
2019-09-07 10:35     ` Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 15/28] xen/arm32: head: Rework and document zero_bss() Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 16/28] xen/arm32: head: Document create_pages_tables() Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 17/28] xen/arm32: head: Document enable_mmu() Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 18/28] xen/arm32: head: Move assembly switch to the runtime PT in secondary CPUs path Julien Grall
2019-08-22 17:17   ` Stefano Stabellini
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 19/28] xen/arm32: head: Don't setup the fixmap on secondary CPUs Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 20/28] xen/arm32: head: Remove 1:1 mapping as soon as it is not used Julien Grall
2019-08-22 18:17   ` Stefano Stabellini
2019-08-22 18:31     ` Julien Grall
2019-08-22 22:53       ` Stefano Stabellini
2019-08-22 23:39         ` Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 21/28] xen/arm32: head: Rework and document setup_fixmap() Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 22/28] xen/arm32: head: Rework and document launch() Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 23/28] xen/arm32: head: Setup HTTBR in enable_mmu() and add missing isb Julien Grall
2019-08-22 17:15   ` Stefano Stabellini
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 24/28] xen/arm: Zero BSS after the MMU and D-cache is turned on Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 25/28] xen/arm64: head: Introduce macros to create table and mapping entry Julien Grall
2019-08-22 23:31   ` Stefano Stabellini
2019-08-22 23:44     ` Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 26/28] xen/arm64: head: Use a page mapping for the 1:1 mapping in create_page_tables() Julien Grall
2019-08-24  1:16   ` Stefano Stabellini
2019-09-17 17:53     ` Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 27/28] xen/arm32: head: Introduce macros to create table and mapping entry Julien Grall
2019-08-23  1:10   ` Stefano Stabellini
2019-08-23  9:40     ` Julien Grall
2019-08-12 17:30 ` [Xen-devel] [PATCH v3 28/28] xen/arm32: head: Use a page mapping for the 1:1 mapping in create_page_tables() Julien Grall

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