Re: [PATCH gnumach] apic: Set up LAPICs in xAPIC mode

[Samuel Thibault]

Hello,

Damien Zammit, le lun. 29 janv. 2024 10:06:38 +0000, a ecrit:
> Clear flag in msr for xAPIC mode.
> 
> ---
>  i386/i386/apic.h      | 3 ++-
>  i386/i386/cpuboot.S   | 3 ++-
>  i386/i386at/boothdr.S | 3 ++-
>  3 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/i386/i386/apic.h b/i386/i386/apic.h
> index e870dcf8..9f908159 100644
> --- a/i386/i386/apic.h
> +++ b/i386/i386/apic.h
> @@ -298,7 +298,8 @@ extern int cpu_id_lut[];
>  
>  #define APIC_MSR                       0x1b
>  #define APIC_MSR_BSP                   0x100 /* Processor is a BSP */
> -#define APIC_MSR_ENABLE                0x800
> +#define APIC_MSR_X2APIC                0x400 /* LAPIC is in x2APIC mode */
> +#define APIC_MSR_ENABLE                0x800 /* LAPIC is enabled */
>  
>  /* Set or clear a bit in a 255-bit APIC mask register.
>     These registers are spread through eight 32-bit registers.  */
> diff --git a/i386/i386/cpuboot.S b/i386/i386/cpuboot.S
> index c85c4ddb..6c3cfcb3 100644
> --- a/i386/i386/cpuboot.S
> +++ b/i386/i386/cpuboot.S
> @@ -175,13 +175,14 @@ _apboot:
>       mov     apboot_idt_ptr, %ebx
>       lidt    (%ebx)
>  
> -     /* Enable local apic */
> +     /* Enable local apic in xAPIC mode */
>       xorl    %eax, %eax
>       xorl    %edx, %edx
>       movl    $APIC_MSR, %ecx
>       rdmsr
>       orl     $APIC_MSR_ENABLE, %eax
>       andl    $(~APIC_MSR_BSP), %eax
> +     andl    $(~APIC_MSR_X2APIC), %eax

You can probably integrate the two andl:

        andl    $(~(APIC_MSR_BSP | APIC_MSR_X2APIC)), %eax

>       movl    $APIC_MSR, %ecx
>       wrmsr
>  
> diff --git a/i386/i386at/boothdr.S b/i386/i386at/boothdr.S
> index 6696d966..daaf57db 100644
> --- a/i386/i386at/boothdr.S
> +++ b/i386/i386at/boothdr.S
> @@ -67,13 +67,14 @@ boot_entry:
>       movl    $solid_intstack+INTSTACK_SIZE-4, %esp
>       andl    $0xfffffff0,%esp
>  
> -     /* Enable local apic */
> +     /* Enable local apic in xAPIC mode */
>       xorl    %eax, %eax
>       xorl    %edx, %edx
>       movl    $APIC_MSR, %ecx
>       rdmsr
>       orl     $APIC_MSR_ENABLE, %eax
>       orl     $APIC_MSR_BSP, %eax
> +     andl    $(~APIC_MSR_X2APIC), %eax
>       movl    $APIC_MSR, %ecx
>       wrmsr
>  
> -- 
> 2.43.0
> 
> 
>