Re: [Minios-devel] [UNIKRAFT PATCH 3/3] plat/kvm: set write protect flag in CR0

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

Reviewed-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>

On 30.05.19 22:52, Florian Schmidt wrote:
> The last patch introduced read-only pages into the page table. However,
> unless the WP flag is set in CR0, this information is ignored in
> supervisor (i.e., kernel) mode. So set it at boot time to enable write
> protection of pages.
>
> Signed-off-by: Florian Schmidt <florian.schmidt@xxxxxxxxx>
> ---
>   plat/common/include/x86/cpu_defs.h | 1 +
>   plat/kvm/x86/entry64.S             | 2 +-
>   2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/plat/common/include/x86/cpu_defs.h 
> b/plat/common/include/x86/cpu_defs.h
> index e968a832..107f0f0a 100644
> --- a/plat/common/include/x86/cpu_defs.h
> +++ b/plat/common/include/x86/cpu_defs.h
> @@ -60,6 +60,7 @@
>   #define X86_CR0_EM              (1 << 2)    /* Emulation */
>   #define X86_CR0_TS              (1 << 3)    /* Task Switched */
>   #define X86_CR0_NE              (1 << 5)    /* Numeric Exception */
> +#define X86_CR0_WP              (1 << 16)   /* Write Protect */
>   #define X86_CR0_PG              (1 << 31)   /* Paging */
>   
>   /*
> diff --git a/plat/kvm/x86/entry64.S b/plat/kvm/x86/entry64.S
> index 828cd1bc..274ab0b3 100644
> --- a/plat/kvm/x86/entry64.S
> +++ b/plat/kvm/x86/entry64.S
> @@ -184,7 +184,7 @@ ENTRY(_libkvmplat_start64)
>         /* FPU and SSE are part of base x86-64, so no need to check for their
>          * availability before enabling and initializing. */
>         andl $(~(X86_CR0_EM | X86_CR0_TS)), %esi
> -       orl $(X86_CR0_MP | X86_CR0_NE), %esi
> +       orl $(X86_CR0_MP | X86_CR0_NE | X86_CR0_WP), %esi
>         movq %rsi, %cr0
>         fninit
>   #if __SSE__
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