Re: [PATCH v7 03/17] KVM: s390: pv: handle secure storage exceptions for normal guests

Janosch Frank
2022-02-07T10:00:48Z

On 2/4/22 16:53, Claudio Imbrenda wrote:
> With upcoming patches, normal guests might touch secure pages.
>
> This patch extends the existing exception handler to convert the pages
> to non secure also when the exception is triggered by a normal guest.
>
> This can happen for example when a secure guest reboots; the first
> stage of a secure guest is non secure, and in general a secure guest
> can reboot into non-secure mode.
>
> If the secure memory of the previous boot has not been cleared up
> completely yet (which will be allowed to happen in an upcoming patch),
> a non-secure guest might touch secure memory, which will need to be
> handled properly.
>
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Once you fix the compiler warning:
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

> ---
> arch/s390/mm/fault.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
> index 47b52e5384f8..bbd37e2c7962 100644
> --- a/arch/s390/mm/fault.c
> +++ b/arch/s390/mm/fault.c
> @@ -770,6 +770,7 @@ void do_secure_storage_access(struct pt_regs *regs)
> struct vm_area_struct *vma;
> struct mm_struct *mm;
> struct page *page;
> + struct gmap *gmap;
> int rc;
>
> /*
> @@ -799,6 +800,16 @@ void do_secure_storage_access(struct pt_regs *regs)
> }
>
> switch (get_fault_type(regs)) {
> + case GMAP_FAULT:
> + gmap = (struct gmap *)S390_lowcore.gmap;
> + mmap_read_lock(mm);
> + addr = __gmap_translate(gmap, addr);
> + mmap_read_unlock(mm);
> + if (IS_ERR_VALUE(addr)) {
> + do_fault_error(regs, VM_ACCESS_FLAGS, VM_FAULT_BADMAP);
> + break;
> + }
> + fallthrough;
> case USER_FAULT:
> mm = current->mm;
> mmap_read_lock(mm);
> @@ -827,7 +838,6 @@ void do_secure_storage_access(struct pt_regs *regs)
> if (rc)
> BUG();
> break;
> - case GMAP_FAULT:
> default:
> do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
> WARN_ON_ONCE(1);
>