Re: [Xen-devel] [PATCH] x86/HVM: replace open-coded non-local cache flushing

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 04/25/2014 06:51 AM, Jan Beulich wrote:
> We accumulated quite a number of these, despite having a pre-canned
> interface for it.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

Somewhat related: I also noticed that in on_selected_cpus() (that this 
patch is replacing for flushing) we take a global lock. I wonder whether 
this may cause scaling issues on big systems. (The same would be true 
for flush_all/mask but to a lesser extent since at least that's a lock 
dedicated to a particular operation)
-boris

> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -1823,11 +1823,6 @@ static bool_t domain_exit_uc_mode(struct
>       return 1;
>   }
>   
> -static void local_flush_cache(void *info)
> -{
> -    wbinvd();
> -}
> -
>   static void hvm_set_uc_mode(struct vcpu *v, bool_t is_in_uc_mode)
>   {
>       v->domain->arch.hvm_domain.is_in_uc_mode = is_in_uc_mode;
> @@ -1927,7 +1922,7 @@ void hvm_shadow_handle_cd(struct vcpu *v
>               domain_pause_nosync(v->domain);
>   
>               /* Flush physical caches. */
> -            on_each_cpu(local_flush_cache, NULL, 1);
> +            flush_all(FLUSH_CACHE);
>               hvm_set_uc_mode(v, 1);
>   
>               domain_unpause(v->domain);
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -2106,15 +2106,10 @@ static void svm_vmexit_mce_intercept(
>       }
>   }
>   
> -static void wbinvd_ipi(void *info)
> -{
> -    wbinvd();
> -}
> -
>   static void svm_wbinvd_intercept(void)
>   {
>       if ( cache_flush_permitted(current->domain) )
> -        on_each_cpu(wbinvd_ipi, NULL, 1);
> +        flush_all(FLUSH_CACHE);
>   }
>   
>   static void svm_vmexit_do_invalidate_cache(struct cpu_user_regs *regs)
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -1301,11 +1301,6 @@ void vm_resume_fail(void)
>       domain_crash_synchronous();
>   }
>   
> -static void wbinvd_ipi(void *info)
> -{
> -    wbinvd();
> -}
> -
>   void vmx_do_resume(struct vcpu *v)
>   {
>       bool_t debug_state;
> @@ -1332,7 +1327,7 @@ void vmx_do_resume(struct vcpu *v)
>           {
>               int cpu = v->arch.hvm_vmx.active_cpu;
>               if ( cpu != -1 )
> -                on_selected_cpus(cpumask_of(cpu), wbinvd_ipi, NULL, 1);
> +                flush_mask(cpumask_of(cpu), FLUSH_CACHE);
>           }
>   
>           vmx_clear_vmcs(v);
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2307,18 +2307,13 @@ static void vmx_do_extint(struct cpu_use
>       do_IRQ(regs);
>   }
>   
> -static void wbinvd_ipi(void *info)
> -{
> -    wbinvd();
> -}
> -
>   static void vmx_wbinvd_intercept(void)
>   {
>       if ( !cache_flush_permitted(current->domain) || iommu_snoop )
>           return;
>   
>       if ( cpu_has_wbinvd_exiting )
> -        on_each_cpu(wbinvd_ipi, NULL, 1);
> +        flush_all(FLUSH_CACHE);
>       else
>           wbinvd();
>   }

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