Re: [Minios-devel] [UNIKRAFT PATCH v2 2/9] plat/kvm: Make mxcsr_ptr in entry64.S a 32-bit value

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

Reviewed-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>

Florian Schmidt <florian.schmidt@xxxxxxxxx> writes:

> LDMXCSR reads 32 bits into the register. If mxcsr_ptr is only a .word
> (and thus 16 bits), the instruction reads adjacent bytes into the MXCSR
> register, which can to produce #GP faults on LDMXCSR when those adjacent
> bytes contain 1's in bit locations that are reserved in MXCSR.
>
> Signed-off-by: Florian Schmidt <florian.schmidt@xxxxxxxxx>
> ---
>  plat/kvm/x86/entry64.S | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/plat/kvm/x86/entry64.S b/plat/kvm/x86/entry64.S
> index 35738b67..dc3614a2 100644
> --- a/plat/kvm/x86/entry64.S
> +++ b/plat/kvm/x86/entry64.S
> @@ -160,8 +160,7 @@ gdt64_ptr:
>  
>  .type mxcsr_ptr, @object
>  mxcsr_ptr:
> -     .word 0x1f80                    /* Intel SDM power-on default */
> -
> +     .long 0x1f80                    /* Intel SDM power-on default */
>  
>  
>  #include "pagetable.S"
> -- 
> 2.19.2
>

-- 
Yuri Volchkov
Software Specialist

NEC Europe Ltd
Kurfürsten-Anlage 36
D-69115 Heidelberg

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