Re: [PATCH 4/4] s390/mm: disable KSM for storage key enabled pages

[Paolo Bonzini]

Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

(missing R-b on patch 1 is _not_ a mistake :))

Paolo

On 10/22/2014 01:09 PM, Dominik Dingel wrote:
> When storage keys are enabled unmerge already merged pages and prevent
> new pages from being merged.
> 
> Signed-off-by: Dominik Dingel <dingel@xxxxxxxxxxxxxxxxxx>
> Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
>  arch/s390/include/asm/pgtable.h |  2 +-
>  arch/s390/kvm/priv.c            | 17 ++++++++++++-----
>  arch/s390/mm/pgtable.c          | 16 +++++++++++++++-
>  3 files changed, 28 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index 0da98d6..dfb38af 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -1754,7 +1754,7 @@ static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
>  extern int vmem_add_mapping(unsigned long start, unsigned long size);
>  extern int vmem_remove_mapping(unsigned long start, unsigned long size);
>  extern int s390_enable_sie(void);
> -extern void s390_enable_skey(void);
> +extern int s390_enable_skey(void);
>  extern void s390_reset_cmma(struct mm_struct *mm);
>  
>  /*
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index f89c1cd..e0967fd 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -156,21 +156,25 @@ static int handle_store_cpu_address(struct kvm_vcpu *vcpu)
>  	return 0;
>  }
>  
> -static void __skey_check_enable(struct kvm_vcpu *vcpu)
> +static int __skey_check_enable(struct kvm_vcpu *vcpu)
>  {
> +	int rc = 0;
>  	if (!(vcpu->arch.sie_block->ictl & (ICTL_ISKE | ICTL_SSKE | ICTL_RRBE)))
> -		return;
> +		return rc;
>  
> -	s390_enable_skey();
> +	rc = s390_enable_skey();
>  	trace_kvm_s390_skey_related_inst(vcpu);
>  	vcpu->arch.sie_block->ictl &= ~(ICTL_ISKE | ICTL_SSKE | ICTL_RRBE);
> +	return rc;
>  }
>  
>  
>  static int handle_skey(struct kvm_vcpu *vcpu)
>  {
> -	__skey_check_enable(vcpu);
> +	int rc = __skey_check_enable(vcpu);
>  
> +	if (rc)
> +		return rc;
>  	vcpu->stat.instruction_storage_key++;
>  
>  	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> @@ -692,7 +696,10 @@ static int handle_pfmf(struct kvm_vcpu *vcpu)
>  		}
>  
>  		if (vcpu->run->s.regs.gprs[reg1] & PFMF_SK) {
> -			__skey_check_enable(vcpu);
> +			int rc = __skey_check_enable(vcpu);
> +
> +			if (rc)
> +				return rc;
>  			if (set_guest_storage_key(current->mm, useraddr,
>  					vcpu->run->s.regs.gprs[reg1] & PFMF_KEY,
>  					vcpu->run->s.regs.gprs[reg1] & PFMF_NQ))
> diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
> index 58d7eb2..82aa528 100644
> --- a/arch/s390/mm/pgtable.c
> +++ b/arch/s390/mm/pgtable.c
> @@ -18,6 +18,8 @@
>  #include <linux/rcupdate.h>
>  #include <linux/slab.h>
>  #include <linux/swapops.h>
> +#include <linux/ksm.h>
> +#include <linux/mman.h>
>  
>  #include <asm/pgtable.h>
>  #include <asm/pgalloc.h>
> @@ -1328,22 +1330,34 @@ static int __s390_enable_skey(pte_t *pte, unsigned long addr,
>  	return 0;
>  }
>  
> -void s390_enable_skey(void)
> +int s390_enable_skey(void)
>  {
>  	struct mm_walk walk = { .pte_entry = __s390_enable_skey };
>  	struct mm_struct *mm = current->mm;
> +	struct vm_area_struct *vma;
> +	int rc = 0;
>  
>  	down_write(&mm->mmap_sem);
>  	if (mm_use_skey(mm))
>  		goto out_up;
>  
>  	mm->context.use_skey = 1;
> +	for (vma = mm->mmap; vma; vma = vma->vm_next) {
> +		if (ksm_madvise(vma, vma->vm_start, vma->vm_end,
> +				MADV_UNMERGEABLE, &vma->vm_flags)) {
> +			mm->context.use_skey = 0;
> +			rc = -ENOMEM;
> +			goto out_up;
> +		}
> +	}
> +	mm->def_flags &= ~VM_MERGEABLE;
>  
>  	walk.mm = mm;
>  	walk_page_range(0, TASK_SIZE, &walk);
>  
>  out_up:
>  	up_write(&mm->mmap_sem);
> +	return rc;
>  }
>  EXPORT_SYMBOL_GPL(s390_enable_skey);
>  
> 
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