[kvm-unit-tests PATCH v2 5/7] lib: s390x: Use a new asce for each PV guest

[Janosch Frank <frankja@linux.ibm.com>]

Every PV guest needs its own ASCE so let's copy the topmost table
designated by CR1 to create a new ASCE for the PV guest. Before and
after SIE we now need to switch ASCEs to and from the PV guest / test
ASCE. The SIE assembly function does that automatically.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
---
 lib/s390x/asm-offsets.c |  2 ++
 lib/s390x/sie.c         |  2 ++
 lib/s390x/sie.h         |  2 ++
 lib/s390x/uv.c          | 24 +++++++++++++++++++++++-
 lib/s390x/uv.h          |  5 ++---
 s390x/cpu.S             |  6 ++++++
 6 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/lib/s390x/asm-offsets.c b/lib/s390x/asm-offsets.c
index fbea3278..f612f327 100644
--- a/lib/s390x/asm-offsets.c
+++ b/lib/s390x/asm-offsets.c
@@ -75,9 +75,11 @@ int main(void)
 	OFFSET(SIE_SAVEAREA_HOST_GRS, vm_save_area, host.grs[0]);
 	OFFSET(SIE_SAVEAREA_HOST_FPRS, vm_save_area, host.fprs[0]);
 	OFFSET(SIE_SAVEAREA_HOST_FPC, vm_save_area, host.fpc);
+	OFFSET(SIE_SAVEAREA_HOST_ASCE, vm_save_area, host.asce);
 	OFFSET(SIE_SAVEAREA_GUEST_GRS, vm_save_area, guest.grs[0]);
 	OFFSET(SIE_SAVEAREA_GUEST_FPRS, vm_save_area, guest.fprs[0]);
 	OFFSET(SIE_SAVEAREA_GUEST_FPC, vm_save_area, guest.fpc);
+	OFFSET(SIE_SAVEAREA_GUEST_ASCE, vm_save_area, guest.asce);
 	OFFSET(STACK_FRAME_INT_BACKCHAIN, stack_frame_int, back_chain);
 	OFFSET(STACK_FRAME_INT_FPC, stack_frame_int, fpc);
 	OFFSET(STACK_FRAME_INT_FPRS, stack_frame_int, fprs);
diff --git a/lib/s390x/sie.c b/lib/s390x/sie.c
index 3fee3def..6efad965 100644
--- a/lib/s390x/sie.c
+++ b/lib/s390x/sie.c
@@ -85,6 +85,8 @@ void sie_guest_create(struct vm *vm, uint64_t guest_mem, uint64_t guest_mem_len)
 
 	/* Guest memory chunks are always 1MB */
 	assert(!(guest_mem_len & ~HPAGE_MASK));
+	/* For non-PV guests we re-use the host's ASCE for ease of use */
+	vm->save_area.guest.asce = stctg(1);
 	/* Currently MSO/MSL is the easiest option */
 	vm->sblk->mso = (uint64_t)guest_mem;
 	vm->sblk->msl = (uint64_t)guest_mem + ((guest_mem_len - 1) & HPAGE_MASK);
diff --git a/lib/s390x/sie.h b/lib/s390x/sie.h
index 320c4218..3e3605c9 100644
--- a/lib/s390x/sie.h
+++ b/lib/s390x/sie.h
@@ -205,12 +205,14 @@ union {
 struct vm_uv {
 	uint64_t vm_handle;
 	uint64_t vcpu_handle;
+	uint64_t asce;
 	void *conf_base_stor;
 	void *conf_var_stor;
 	void *cpu_stor;
 };
 
 struct vm_save_regs {
+	uint64_t asce;
 	uint64_t grs[16];
 	uint64_t fprs[16];
 	uint32_t fpc;
diff --git a/lib/s390x/uv.c b/lib/s390x/uv.c
index 3b4cafa9..0b6eb843 100644
--- a/lib/s390x/uv.c
+++ b/lib/s390x/uv.c
@@ -90,6 +90,25 @@ void uv_init(void)
 	initialized = true;
 }
 
+/*
+ * Create a new ASCE for the UV config because they can't be shared
+ * for security reasons. We just simply copy the top most table into a
+ * fresh set of allocated pages and use those pages as the asce.
+ */
+static uint64_t create_asce(void)
+{
+	void *pgd_new, *pgd_old;
+	uint64_t asce = stctg(1);
+
+	pgd_new = memalign_pages_flags(PAGE_SIZE, PAGE_SIZE * 4, 0);
+	pgd_old = (void *)(asce & PAGE_MASK);
+
+	memcpy(pgd_new, pgd_old, PAGE_SIZE * 4);
+
+	asce = __pa(pgd_new) | ASCE_DT_REGION1 | REGION_TABLE_LENGTH | ASCE_P;
+	return asce;
+}
+
 void uv_create_guest(struct vm *vm)
 {
 	struct uv_cb_cgc uvcb_cgc = {
@@ -125,7 +144,8 @@ void uv_create_guest(struct vm *vm)
 	vm->uv.cpu_stor = memalign_pages_flags(PAGE_SIZE, uvcb_qui.cpu_stor_len, 0);
 	uvcb_csc.stor_origin = (uint64_t)vm->uv.cpu_stor;
 
-	uvcb_cgc.guest_asce = (uint64_t)stctg(1);
+	uvcb_cgc.guest_asce = create_asce();
+	vm->save_area.guest.asce = uvcb_cgc.guest_asce;
 	uvcb_cgc.guest_sca = (uint64_t)vm->sca;
 
 	cc = uv_call(0, (uint64_t)&uvcb_cgc);
@@ -166,6 +186,8 @@ void uv_destroy_guest(struct vm *vm)
 	assert(cc == 0);
 	free_pages(vm->uv.conf_base_stor);
 	free_pages(vm->uv.conf_var_stor);
+
+	free_pages((void *)(vm->uv.asce & PAGE_MASK));
 }
 
 int uv_unpack(struct vm *vm, uint64_t addr, uint64_t len, uint64_t tweak)
diff --git a/lib/s390x/uv.h b/lib/s390x/uv.h
index 44264861..5fe29bda 100644
--- a/lib/s390x/uv.h
+++ b/lib/s390x/uv.h
@@ -28,9 +28,8 @@ static inline void uv_setup_asces(void)
 	/* We need to have a valid primary ASCE to run guests. */
 	setup_vm();
 
-	/* Set P bit in ASCE as it is required for PV guests */
-	asce = stctg(1) | ASCE_P;
-	lctlg(1, asce);
+	/* Grab the ASCE which setup_vm() just set up */
+	asce = stctg(1);
 
 	/* Copy ASCE into home space CR */
 	lctlg(13, asce);
diff --git a/s390x/cpu.S b/s390x/cpu.S
index 82b5e25d..45bd551a 100644
--- a/s390x/cpu.S
+++ b/s390x/cpu.S
@@ -76,6 +76,9 @@ sie64a:
 	.endr
 	stfpc	SIE_SAVEAREA_HOST_FPC(%r3)
 
+	stctg	%c1, %c1, SIE_SAVEAREA_HOST_ASCE(%r3)
+	lctlg	%c1, %c1, SIE_SAVEAREA_GUEST_ASCE(%r3)
+
 	# Store scb and save_area pointer into stack frame
 	stg	%r2,__SF_SIE_CONTROL(%r15)	# save control block pointer
 	stg	%r3,__SF_SIE_SAVEAREA(%r15)	# save guest register save area
@@ -102,6 +105,9 @@ sie_exit:
 	# Load guest register save area
 	lg	%r14,__SF_SIE_SAVEAREA(%r15)
 
+	# Restore the host asce
+	lctlg	%c1, %c1, SIE_SAVEAREA_HOST_ASCE(%r14)
+
 	# Store guest's gprs, fprs and fpc
 	stmg	%r0,%r13,SIE_SAVEAREA_GUEST_GRS(%r14)	# save guest gprs 0-13
 	.irp i, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-- 
2.34.1