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 ?
> + 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>
