On 10/24/19 6:07 PM, David Hildenbrand wrote:
> On 24.10.19 13:40, Janosch Frank wrote:
>> KSM will not work on secure pages, because when the kernel reads a
>> secure page, it will be encrypted and hence no two pages will look the
>> same.
>>
>> Let's mark the guest pages as unmergeable when we transition to secure
>> mode.
>>
>> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
>> ---
>> arch/s390/include/asm/gmap.h | 1 +
>> arch/s390/kvm/kvm-s390.c | 6 ++++++
>> arch/s390/mm/gmap.c | 28 ++++++++++++++++++----------
>> 3 files changed, 25 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
>> index 6efc0b501227..eab6a2ec3599 100644
>> --- a/arch/s390/include/asm/gmap.h
>> +++ b/arch/s390/include/asm/gmap.h
>> @@ -145,4 +145,5 @@ int gmap_mprotect_notify(struct gmap *, unsigned long start,
>>
>> void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
>> unsigned long gaddr, unsigned long vmaddr);
>> +int gmap_mark_unmergeable(void);
>> #endif /* _ASM_S390_GMAP_H */
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 924132d92782..d1ba12f857e7 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -2176,6 +2176,12 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
>> if (r)
>> break;
>>
>> + down_write(¤t->mm->mmap_sem);
>> + r = gmap_mark_unmergeable();
>> + up_write(¤t->mm->mmap_sem);
>> + if (r)
>> + break;
>> +
>> mutex_lock(&kvm->lock);
>> kvm_s390_vcpu_block_all(kvm);
>> /* FMT 4 SIE needs esca */
>> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
>> index edcdca97e85e..bf365a09f900 100644
>> --- a/arch/s390/mm/gmap.c
>> +++ b/arch/s390/mm/gmap.c
>> @@ -2548,6 +2548,23 @@ int s390_enable_sie(void)
>> }
>> EXPORT_SYMBOL_GPL(s390_enable_sie);
>>
>> +int gmap_mark_unmergeable(void)
>> +{
>> + struct mm_struct *mm = current->mm;
>> + struct vm_area_struct *vma;
>> +
>> + 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.uses_skeys = 0;
>
> That skey setting does not make too much sense when coming via
> kvm_s390_handle_pv(). handle that in the caller?
Hmm, I think the name of that variable is just plain wrong.
It should be "can_use_skeys" or "uses_unmergeable" (which would fit
better into the mm context anyway) and then we could add a
kvm->arch.uses_skeys to tell that we actually used them for migration
checks, etc..
I had long discussions with Martin over these variable names a long time
ago..
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