[PATCH v2 05/13] KVM: s390: pv: handle secure storage exceptions for normal guests

Claudio Imbrenda
2021-07-28T14:27:35Z

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, a non-secure guest might touch secure memory, which
will need to be handled properly.

Signed-off-by: Claudio Imbrenda <imbrenda@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 eb68b4f36927..b89d625ea2ec 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -767,6 +767,7 @@ 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;

/*
@@ -796,6 +797,16 @@ void do_secure_storage_access(struct pt_regs *regs)
}

switch (get_fault_type(regs)) {
+ case GMAP_FAULT:
+ gmap = (struct gmap *)S390_lowcore.gmap;
+ /*
+ * Very unlikely, but if it happens, simply try again.
+ * The next attempt will trigger a different exception.
+ */
+ addr = __gmap_translate(gmap, addr);
+ if (addr == -EFAULT)
+ break;
+ fallthrough;
case USER_FAULT:
mm = current->mm;
mmap_read_lock(mm);
@@ -824,7 +835,6 @@ 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);
--
2.31.1