On 04.02.20 21:52, Thomas Huth wrote:
> On 03/02/2020 14.19, Christian Borntraeger wrote:
>> Before we destroy the secure configuration, we better make all
>> pages accessible again. This also happens during reboot, where we reboot
>> into a non-secure guest that then can go again into a secure mode. As
>> this "new" secure guest will have a new ID we cannot reuse the old page
>> state.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>> ---
>> arch/s390/include/asm/pgtable.h | 1 +
>> arch/s390/kvm/pv.c | 2 ++
>> arch/s390/mm/gmap.c | 35 +++++++++++++++++++++++++++++++++
>> 3 files changed, 38 insertions(+)
>>
>> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
>> index 65b6bb47af0a..6e167dcc35f1 100644
>> --- a/arch/s390/include/asm/pgtable.h
>> +++ b/arch/s390/include/asm/pgtable.h
>> @@ -1669,6 +1669,7 @@ extern int vmem_remove_mapping(unsigned long start, unsigned long size);
>> extern int s390_enable_sie(void);
>> extern int s390_enable_skey(void);
>> extern void s390_reset_cmma(struct mm_struct *mm);
>> +extern void s390_reset_acc(struct mm_struct *mm);
>>
>> /* s390 has a private copy of get unmapped area to deal with cache synonyms */
>> #define HAVE_ARCH_UNMAPPED_AREA
>> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
>> index a867b9e9c069..24d802072ac7 100644
>> --- a/arch/s390/kvm/pv.c
>> +++ b/arch/s390/kvm/pv.c
>> @@ -66,6 +66,8 @@ int kvm_s390_pv_destroy_vm(struct kvm *kvm)
>> int rc;
>> u32 ret;
>>
>> + /* make all pages accessible before destroying the guest */
>> + s390_reset_acc(kvm->mm);
>> rc = uv_cmd_nodata(kvm_s390_pv_handle(kvm),
>> UVC_CMD_DESTROY_SEC_CONF, &ret);
>> WRITE_ONCE(kvm->arch.gmap->se_handle, 0);
>> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
>> index bf365a09f900..0b00e8d5fa39 100644
>> --- a/arch/s390/mm/gmap.c
>> +++ b/arch/s390/mm/gmap.c
>> @@ -2648,3 +2648,38 @@ void s390_reset_cmma(struct mm_struct *mm)
>> up_write(&mm->mmap_sem);
>> }
>> EXPORT_SYMBOL_GPL(s390_reset_cmma);
>> +
>> +/*
>> + * make inaccessible pages accessible again
>> + */
>> +static int __s390_reset_acc(pte_t *ptep, unsigned long addr,
>> + unsigned long next, struct mm_walk *walk)
>> +{
>> + pte_t pte = READ_ONCE(*ptep);
>> +
>> + if (pte_present(pte))
>> + uv_convert_from_secure(pte_val(pte) & PAGE_MASK);
>
> Is it ok to ignore the return value from uv_convert_from_secure() ?
> Problems might go unnoticed ... maybe use at least a WARN_ONCE ?
Hmm, it is certainly one of these "should not happen" cases.
So yes, I will add a WARN_ON_ONCE.
>
>> + return 0;
>> +}
>> +
>> +static const struct mm_walk_ops reset_acc_walk_ops = {
>> + .pte_entry = __s390_reset_acc,
>> +};
>> +
>> +#include <linux/sched/mm.h>
>> +void s390_reset_acc(struct mm_struct *mm)
>> +{
>> + /*
>> + * we might be called during
>> + * reset: we walk the pages and clear
>> + * close of all kvm file descriptor: we walk the pages and clear
>> + * exit of process on fd closure: vma already gone, do nothing
>> + */
>> + if (!mmget_not_zero(mm))
>> + return;
>> + down_read(&mm->mmap_sem);
>> + walk_page_range(mm, 0, TASK_SIZE, &reset_acc_walk_ops, NULL);
>> + up_read(&mm->mmap_sem);
>> + mmput(mm);
>> +}
>> +EXPORT_SYMBOL_GPL(s390_reset_acc);
>>
>
> Anyway,
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
>
thanks.
