Re: [Xen-devel] [PATCH] Revert "VMX: flush cache when vmentry back to UC guest"

["Liu, Jinsong" <jinsong.liu@xxxxxxxxx>]

Jan Beulich wrote:
> This reverts commit 86d60e85 as well as one related change from
> 62652c00 ("VMX: fix cr0.cd handling"), on the basis that all of this
> flushing is still insufficient and, while not known to fix anything,
> is known to negatively affect performance.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Liu Jinsong <jinsong.liu@xxxxxxxxx>

> 
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -2566,9 +2566,6 @@ static enum hvm_copy_result __hvm_copy(
>          return HVMCOPY_unhandleable;
>  #endif
> 
> -    if ( unlikely(curr->arch.hvm_vcpu.cache_mode ==
> NO_FILL_CACHE_MODE) ) 
> -        curr->arch.hvm_vcpu.hypervisor_access_uc_hvm_memory = 1;
> -
>      while ( todo > 0 )
>      {
>          count = min_t(int, PAGE_SIZE - (addr & ~PAGE_MASK), todo);
> @@ -2680,9 +2677,6 @@ static enum hvm_copy_result __hvm_clear(
>          return HVMCOPY_unhandleable;
>  #endif
> 
> -    if ( unlikely(curr->arch.hvm_vcpu.cache_mode ==
> NO_FILL_CACHE_MODE) ) 
> -        curr->arch.hvm_vcpu.hypervisor_access_uc_hvm_memory = 1;
> -
>      while ( todo > 0 )
>      {
>          count = min_t(int, PAGE_SIZE - (addr & ~PAGE_MASK), todo);
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -643,10 +643,6 @@ static void vmx_ctxt_switch_to(struct vc
>              __invept(INVEPT_SINGLE_CONTEXT, ept_get_eptp(ept_data),
>      0); }
> 
> -    /* For guest cr0.cd setting, do not use potentially polluted
> cache */ 
> -    if ( unlikely(v->arch.hvm_vcpu.cache_mode == NO_FILL_CACHE_MODE)
> ) 
> -        wbinvd();
> -
>      vmx_restore_guest_msrs(v);
>      vmx_restore_dr(v);
>  }
> @@ -2999,13 +2995,6 @@ void vmx_vmenter_helper(const struct cpu
>      struct hvm_vcpu_asid *p_asid;
>      bool_t need_flush;
> 
> -    /* In case hypervisor access hvm memory when guest uc mode */
> -    if (
> unlikely(curr->arch.hvm_vcpu.hypervisor_access_uc_hvm_memory) ) 
> -    {
> -        curr->arch.hvm_vcpu.hypervisor_access_uc_hvm_memory = 0;
> -        wbinvd();
> -    }
> -
>      if ( !cpu_has_vmx_vpid )
>          goto out;
>      if ( nestedhvm_vcpu_in_guestmode(curr) )
> --- a/xen/include/asm-x86/hvm/vcpu.h
> +++ b/xen/include/asm-x86/hvm/vcpu.h
> @@ -169,7 +169,6 @@ struct hvm_vcpu {
> 
>      /* Which cache mode is this VCPU in (CR0:CD/NW)? */
>      u8                  cache_mode;
> -    bool_t              hypervisor_access_uc_hvm_memory;
> 
>      struct hvm_vcpu_io  hvm_io;


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel