Re: [Minios-devel] [UNIKRAFT PATCH 6/9] plat/kvm: streamline Firecracker early boot

["Haibo Xu (Arm Technology China)" <Haibo.Xu@xxxxxxx>]

This patch looks good.

Reviewed-by: Haibo Xu <haibo.xu@xxxxxxx>

On 2019/6/3 22:56, Florian Schmidt wrote:
> There are several pieces in the early boot code that are unnecessary
> when building for Firecracker: namely, the multiboot header is not
> required; and the 32-bit setup which forms the very earliest steps of
> the boot process can be skipped because Firecracker drops us off in long
> mode. However, move the page table setup code into the 64-bit part to
> make sure that it is executed.
>
> Signed-off-by: Florian Schmidt <florian.schmidt@xxxxxxxxx>
> ---
>  plat/kvm/x86/entry64.S | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/plat/kvm/x86/entry64.S b/plat/kvm/x86/entry64.S
> index 274ab0b3..186f6ce4 100644
> --- a/plat/kvm/x86/entry64.S
> +++ b/plat/kvm/x86/entry64.S
> @@ -27,6 +27,7 @@
>   * SUCH DAMAGE.
>   */
>
> +#include <uk/config.h>
>  #include <x86/cpu_defs.h>
>  #include <kvm-x86/traps.h>
>  #include <kvm-x86/multiboot_defs.h>
> @@ -37,6 +38,7 @@
>  #define MYMULTIBOOT_FLAGS \
>      (MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE)
>
> +#if KVMQPLAT
>  .section .data.boot
>
>  .align 4
> @@ -50,11 +52,13 @@ _multiboot_header:
>  .long _end                                        /* bss end addr */
>  .long _libkvmplat_start32                         /* entry addr */
>
> +#endif
>  .section .bss
>
>  .space 4096
>  bootstack:
>
> +#if KVMQPLAT
>  /*
>   * Bootloader entry point.
>   *
> @@ -90,15 +94,6 @@ ENTRY(_libkvmplat_start32)
>       orl $X86_EFER_LME, %eax
>       wrmsr
>
> -     /* 3: load pml4 pointer */
> -     movl $cpu_pml4, %eax
> -     movl %eax, %cr3
> -
> -     /* 4: enable paging */
> -     movl %cr0, %eax
> -     orl $X86_CR0_PG, %eax
> -     movl %eax, %cr0
> -
>       jmp _libkvmplat_start64
>
>       /* NOTREACHED */
> @@ -111,6 +106,7 @@ haltme:
>       hlt
>       jmp haltme
>  END(_libkvmplat_start32)
> +#endif
>
>  /*
>   * amd64 programmer's manual:
> @@ -149,6 +145,15 @@ mxcsr_ptr:
>  .section .text.boot
>
>  ENTRY(_libkvmplat_start64)
> +     /* load pml4 pointer */
> +     movq $cpu_pml4, %rax
> +     movq %rax, %cr3
> +
> +     /* enable paging */
> +     movq %cr0, %rax
> +     orl $X86_CR0_PG, %eax
> +     movq %rax, %cr0
> +
>       /* set up the boot stack */
>       movq $bootstack, %rsp
>       xorq %rbp, %rbp
>
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