Re: [Xen-devel] [PATCH v3] x86: do not enable global pages when virtualized on AMD hardware

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.12.2019 16:12, Roger Pau Monne wrote:
> --- a/xen/arch/x86/pv/domain.c
> +++ b/xen/arch/x86/pv/domain.c
> @@ -118,6 +118,19 @@ unsigned long pv_fixup_guest_cr4(const struct vcpu *v, 
> unsigned long cr4)
>              (mmu_cr4_features & PV_CR4_GUEST_VISIBLE_MASK));
>  }
>  
> +static int8_t __read_mostly opt_global_pages = -1;
> +boolean_runtime_param("global-pages", opt_global_pages);
> +
> +static int __init pge_init(void)
> +{
> +    if ( opt_global_pages == -1 )
> +        opt_global_pages = !cpu_has_hypervisor ||
> +                           boot_cpu_data.x86_vendor != X86_VENDOR_AMD;
> +
> +    return 0;
> +}
> +__initcall(pge_init);
> +
>  unsigned long pv_make_cr4(const struct vcpu *v)
>  {
>      const struct domain *d = v->domain;
> @@ -130,7 +143,7 @@ unsigned long pv_make_cr4(const struct vcpu *v)
>       */
>      if ( d->arch.pv.pcid )
>          cr4 |= X86_CR4_PCIDE;
> -    else if ( !d->arch.pv.xpti )
> +    else if ( !d->arch.pv.xpti && opt_global_pages )
>          cr4 |= X86_CR4_PGE;

I'm sorry for noticing this only now, but what about XEN_MINIMAL_CR4,
which includes X86_CR4_PGE?

I also have to admit I'm still feeling uneasy about the runtime
adjustment you permit. I can't point at anything that's wrong in this
regard, but anyway.

Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel