Re: [Xen-devel] [PATCH v6.5 26/26] x86/idle: Clear SPEC_CTRL while idle

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.01.18 at 01:15, <andrew.cooper3@xxxxxxxxxx> wrote:
> @@ -31,6 +33,38 @@ static inline void init_shadow_spec_ctrl_state(void)
>      info->shadow_spec_ctrl = info->use_shadow_spec_ctrl = 0;
>  }
>  
> +/* WARNING! `ret`, `call *`, `jmp *` not safe after this call. */
> +static always_inline void spec_ctrl_enter_idle(struct cpu_info *info)
> +{
> +    uint32_t val = 0;
> +
> +    /*
> +     * Latch the new shadow value, then enable shadowing, then update the 
> MSR.
> +     * There are no SMP issues here; only local processor ordering concerns.
> +     */
> +    info->shadow_spec_ctrl = val;
> +    barrier();
> +    info->use_shadow_spec_ctrl = true;
> +    barrier();
> +    asm volatile (ALTERNATIVE(ASM_NOP3, "wrmsr", X86_FEATURE_XEN_IBRS_SET)
> +                  :: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory");

Missing blanks immediately inside the outermost parentheses (also
another time further down).

Jan


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