Re: [Xen-devel] [PATCH 1/6] x86/AMD Split init_amd() into per-uarch helpers

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Dec 28, 2018 at 12:39:31PM +0000, Andrew Cooper wrote:
> This reduces the complexity of init_amd(), and collects related
> workarounds together.
> 
> It also offers us the opportunity to stop performing workarounds when
> virtualised - doing so is wasteful, as it all involves poking MSRs which
> no hypervisor will let us touch in practice.
> 
> As amd.c has diverged almost entirely from its Linux heratage, start
> switching it to using Xen hypervisor style.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> I've dropped various printk()s about working around some errata, because
> their use was completely inconsistent.  They want to be uniform, whether
> that is missing or present.
> ---
>  xen/arch/x86/cpu/amd.c | 266 
> ++++++++++++++++++++++++++++---------------------
>  1 file changed, 153 insertions(+), 113 deletions(-)
> 
> diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
> index c790416..c3aa1f4 100644
> --- a/xen/arch/x86/cpu/amd.c
> +++ b/xen/arch/x86/cpu/amd.c
> @@ -534,22 +534,165 @@ static void early_init_amd(struct cpuinfo_x86 *c)
>       ctxt_switch_levelling(NULL);
>  }
>  
> +static void init_amd_k8(struct cpuinfo_x86 *c)
> +{
> +    uint64_t val;
> +
> +    /*
> +     * Skip errata workarounds if we are virtualised.  We won't have
> +     * sufficient control of hardware to do anything useful.
> +     */
> +    if ( !cpu_has_hypervisor )

I think you want `if ( cpu_has_hypervisor ) return;` according to the
comment (here and below).

The rest LGTM, as is mostly code movement AFAICT:

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

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