[PATCH 06/35] s390/mm: add (non)secure page access exceptions handlers

[Christian Borntraeger <borntraeger@xxxxxxxxxx>]

From: Vasily Gorbik <gor@xxxxxxxxxxxxx>

Add exceptions handlers performing transparent transition of non-secure
pages to secure (import) upon guest access and secure pages to
non-secure (export) upon hypervisor access.

Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
[frankja@xxxxxxxxxxxxx: adding checks for failures]
Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
[imbrenda@xxxxxxxxxxxxx:  adding a check for gmap fault]
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
[borntraeger@xxxxxxxxxx: patch merging, splitting, fixing]
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
 arch/s390/kernel/pgm_check.S |  4 +-
 arch/s390/mm/fault.c         | 86 ++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kernel/pgm_check.S b/arch/s390/kernel/pgm_check.S
index 59dee9d3bebf..27ac4f324c70 100644
--- a/arch/s390/kernel/pgm_check.S
+++ b/arch/s390/kernel/pgm_check.S
@@ -78,8 +78,8 @@ PGM_CHECK(do_dat_exception)		/* 39 */
 PGM_CHECK(do_dat_exception)		/* 3a */
 PGM_CHECK(do_dat_exception)		/* 3b */
 PGM_CHECK_DEFAULT			/* 3c */
-PGM_CHECK_DEFAULT			/* 3d */
-PGM_CHECK_DEFAULT			/* 3e */
+PGM_CHECK(do_secure_storage_access)	/* 3d */
+PGM_CHECK(do_non_secure_storage_access)	/* 3e */
 PGM_CHECK_DEFAULT			/* 3f */
 PGM_CHECK_DEFAULT			/* 40 */
 PGM_CHECK_DEFAULT			/* 41 */
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 7b0bb475c166..fab4219fa0be 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -38,6 +38,7 @@
 #include <asm/irq.h>
 #include <asm/mmu_context.h>
 #include <asm/facility.h>
+#include <asm/uv.h>
 #include "../kernel/entry.h"
 
 #define __FAIL_ADDR_MASK -4096L
@@ -816,3 +817,88 @@ static int __init pfault_irq_init(void)
 early_initcall(pfault_irq_init);
 
 #endif /* CONFIG_PFAULT */
+
+#if IS_ENABLED(CONFIG_KVM)
+void do_secure_storage_access(struct pt_regs *regs)
+{
+	unsigned long addr = regs->int_parm_long & __FAIL_ADDR_MASK;
+	struct vm_area_struct *vma;
+	struct mm_struct *mm;
+	struct page *page;
+	int rc;
+
+	switch (get_fault_type(regs)) {
+	case USER_FAULT:
+		mm = current->mm;
+		down_read(&mm->mmap_sem);
+		vma = find_vma(mm, addr);
+		if (!vma) {
+			up_read(&mm->mmap_sem);
+			do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
+			break;
+		}
+		page = follow_page(vma, addr, FOLL_WRITE | FOLL_GET);
+		if (IS_ERR_OR_NULL(page)) {
+			up_read(&mm->mmap_sem);
+			break;
+		}
+		if (arch_make_page_accessible(page))
+			send_sig(SIGSEGV, current, 0);
+		put_page(page);
+		up_read(&mm->mmap_sem);
+		break;
+	case KERNEL_FAULT:
+		page = phys_to_page(addr);
+		if (unlikely(!try_get_page(page)))
+			break;
+		rc = arch_make_page_accessible(page);
+		put_page(page);
+		if (rc)
+			BUG();
+		break;
+	case VDSO_FAULT:
+		/* fallthrough */
+	case GMAP_FAULT:
+		/* fallthrough */
+	default:
+		do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
+		WARN_ON_ONCE(1);
+	}
+}
+NOKPROBE_SYMBOL(do_secure_storage_access);
+
+void do_non_secure_storage_access(struct pt_regs *regs)
+{
+	unsigned long gaddr = regs->int_parm_long & __FAIL_ADDR_MASK;
+	struct gmap *gmap = (struct gmap *)S390_lowcore.gmap;
+	struct uv_cb_cts uvcb = {
+		.header.cmd = UVC_CMD_CONV_TO_SEC_STOR,
+		.header.len = sizeof(uvcb),
+		.guest_handle = gmap->guest_handle,
+		.gaddr = gaddr,
+	};
+	int rc;
+
+	if (get_fault_type(regs) != GMAP_FAULT) {
+		do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	rc = uv_make_secure(gmap, gaddr, &uvcb);
+	if (rc == -EINVAL && uvcb.header.rc != 0x104)
+		send_sig(SIGSEGV, current, 0);
+}
+NOKPROBE_SYMBOL(do_non_secure_storage_access);
+
+#else
+void do_secure_storage_access(struct pt_regs *regs)
+{
+	default_trap_handler(regs);
+}
+
+void do_non_secure_storage_access(struct pt_regs *regs)
+{
+	default_trap_handler(regs);
+}
+#endif
-- 
2.24.0