drm/i915/gvt: introduced failsafe mode into vgpu

New failsafe mode is introduced, when we detect guest not supporting
GVT-g.
In failsafe mode, we will ignore all the MMIO and cfg space read/write
from guest.

This patch can fix the issue that when guest kernel or graphics driver
version is too low, there will be a lot of kernel traces in host.

V5: rebased onto latest gvt-staging
V4: changed coding style by Zhenyu and Ping's advice
V3: modified coding style and error messages according to Zhenyu's comment
V2: 1) implemented MMIO/GTT/WP pages read/write logic; 2) used a unified
function to enter failsafe mode

Signed-off-by: Min He <min.he@intel.com>
Signed-off-by: Pei Zhang <pei.zhang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/cfg_space.c

@@ -237,6 +237,9 @@ int intel_vgpu_emulate_cfg_write(struct intel_vgpu *vgpu, unsigned int offset,
 {
 	int ret;
 
+	if (vgpu->failsafe)
+		return 0;
+
 	if (WARN_ON(bytes > 4))
 		return -EINVAL;
 

drivers/gpu/drm/i915/gvt/gvt.h

@@ -143,6 +143,8 @@ struct intel_vgpu {
 	int id;
 	unsigned long handle; /* vGPU handle used by hypervisor MPT modules */
 	bool active;
+	bool pv_notified;
+	bool failsafe;
 	bool resetting;
 	void *sched_data;
 
@@ -449,6 +451,10 @@ struct intel_gvt_ops {
 };
 
 
+enum {
+	GVT_FAILSAFE_UNSUPPORTED_GUEST,
+};
+
 #include "mpt.h"
 
 #endif

drivers/gpu/drm/i915/gvt/handlers.c

@@ -150,10 +150,34 @@ static int render_mmio_to_ring_id(struct intel_gvt *gvt, unsigned int reg)
 #define fence_num_to_offset(num) \
 	(num * 8 + i915_mmio_reg_offset(FENCE_REG_GEN6_LO(0)))
 
+
+static void enter_failsafe_mode(struct intel_vgpu *vgpu, int reason)
+{
+	switch (reason) {
+	case GVT_FAILSAFE_UNSUPPORTED_GUEST:
+		pr_err("Detected your guest driver doesn't support GVT-g.\n");
+		break;
+	default:
+		break;
+	}
+	pr_err("Now vgpu %d will enter failsafe mode.\n", vgpu->id);
+	vgpu->failsafe = true;
+}
+
 static int sanitize_fence_mmio_access(struct intel_vgpu *vgpu,
 		unsigned int fence_num, void *p_data, unsigned int bytes)
 {
 	if (fence_num >= vgpu_fence_sz(vgpu)) {
+
+		/* When guest access oob fence regs without access
+		 * pv_info first, we treat guest not supporting GVT,
+		 * and we will let vgpu enter failsafe mode.
+		 */
+		if (!vgpu->pv_notified) {
+			enter_failsafe_mode(vgpu,
+					GVT_FAILSAFE_UNSUPPORTED_GUEST);
+			return -EINVAL;
+		}
 		gvt_err("vgpu%d: found oob fence register access\n",
 				vgpu->id);
 		gvt_err("vgpu%d: total fence num %d access fence num %d\n",
@@ -1001,6 +1025,7 @@ static int pvinfo_mmio_read(struct intel_vgpu *vgpu, unsigned int offset,
 	if (invalid_read)
 		gvt_err("invalid pvinfo read: [%x:%x] = %x\n",
 				offset, bytes, *(u32 *)p_data);
+	vgpu->pv_notified = true;
 	return 0;
 }
 
@@ -1318,6 +1343,17 @@ static int ring_mode_mmio_write(struct intel_vgpu *vgpu, unsigned int offset,
 	bool enable_execlist;
 
 	write_vreg(vgpu, offset, p_data, bytes);
+
+	/* when PPGTT mode enabled, we will check if guest has called
+	 * pvinfo, if not, we will treat this guest as non-gvtg-aware
+	 * guest, and stop emulating its cfg space, mmio, gtt, etc.
+	 */
+	if (((data & _MASKED_BIT_ENABLE(GFX_PPGTT_ENABLE)) ||
+			(data & _MASKED_BIT_ENABLE(GFX_RUN_LIST_ENABLE)))
+			&& !vgpu->pv_notified) {
+		enter_failsafe_mode(vgpu, GVT_FAILSAFE_UNSUPPORTED_GUEST);
+		return 0;
+	}
 	if ((data & _MASKED_BIT_ENABLE(GFX_RUN_LIST_ENABLE))
 			|| (data & _MASKED_BIT_DISABLE(GFX_RUN_LIST_ENABLE))) {
 		enable_execlist = !!(data & GFX_RUN_LIST_ENABLE);

drivers/gpu/drm/i915/gvt/mmio.c

@@ -57,6 +57,58 @@ int intel_vgpu_gpa_to_mmio_offset(struct intel_vgpu *vgpu, u64 gpa)
 	(reg >= gvt->device_info.gtt_start_offset \
 	 && reg < gvt->device_info.gtt_start_offset + gvt_ggtt_sz(gvt))
 
+static void failsafe_emulate_mmio_rw(struct intel_vgpu *vgpu, uint64_t pa,
+		void *p_data, unsigned int bytes, bool read)
+{
+	struct intel_gvt *gvt = NULL;
+	void *pt = NULL;
+	unsigned int offset = 0;
+
+	if (!vgpu || !p_data)
+		return;
+
+	gvt = vgpu->gvt;
+	mutex_lock(&gvt->lock);
+	offset = intel_vgpu_gpa_to_mmio_offset(vgpu, pa);
+	if (reg_is_mmio(gvt, offset)) {
+		if (read)
+			intel_vgpu_default_mmio_read(vgpu, offset, p_data,
+					bytes);
+		else
+			intel_vgpu_default_mmio_write(vgpu, offset, p_data,
+					bytes);
+	} else if (reg_is_gtt(gvt, offset) &&
+			vgpu->gtt.ggtt_mm->virtual_page_table) {
+		offset -= gvt->device_info.gtt_start_offset;
+		pt = vgpu->gtt.ggtt_mm->virtual_page_table + offset;
+		if (read)
+			memcpy(p_data, pt, bytes);
+		else
+			memcpy(pt, p_data, bytes);
+
+	} else if (atomic_read(&vgpu->gtt.n_write_protected_guest_page)) {
+		struct intel_vgpu_guest_page *gp;
+
+		/* Since we enter the failsafe mode early during guest boot,
+		 * guest may not have chance to set up its ppgtt table, so
+		 * there should not be any wp pages for guest. Keep the wp
+		 * related code here in case we need to handle it in furture.
+		 */
+		gp = intel_vgpu_find_guest_page(vgpu, pa >> PAGE_SHIFT);
+		if (gp) {
+			/* remove write protection to prevent furture traps */
+			intel_vgpu_clean_guest_page(vgpu, gp);
+			if (read)
+				intel_gvt_hypervisor_read_gpa(vgpu, pa,
+						p_data, bytes);
+			else
+				intel_gvt_hypervisor_write_gpa(vgpu, pa,
+						p_data, bytes);
+		}
+	}
+	mutex_unlock(&gvt->lock);
+}
+
 /**
  * intel_vgpu_emulate_mmio_read - emulate MMIO read
  * @vgpu: a vGPU
@@ -75,6 +127,11 @@ int intel_vgpu_emulate_mmio_read(struct intel_vgpu *vgpu, uint64_t pa,
 	unsigned int offset = 0;
 	int ret = -EINVAL;
 
+
+	if (vgpu->failsafe) {
+		failsafe_emulate_mmio_rw(vgpu, pa, p_data, bytes, true);
+		return 0;
+	}
 	mutex_lock(&gvt->lock);
 
 	if (atomic_read(&vgpu->gtt.n_write_protected_guest_page)) {
@@ -188,6 +245,11 @@ int intel_vgpu_emulate_mmio_write(struct intel_vgpu *vgpu, uint64_t pa,
 	u32 old_vreg = 0, old_sreg = 0;
 	int ret = -EINVAL;
 
+	if (vgpu->failsafe) {
+		failsafe_emulate_mmio_rw(vgpu, pa, p_data, bytes, false);
+		return 0;
+	}
+
 	mutex_lock(&gvt->lock);
 
 	if (atomic_read(&vgpu->gtt.n_write_protected_guest_page)) {

drivers/gpu/drm/i915/gvt/vgpu.c

@@ -387,8 +387,12 @@ void intel_gvt_reset_vgpu_locked(struct intel_vgpu *vgpu, bool dmlr,
 		populate_pvinfo_page(vgpu);
 		intel_vgpu_reset_display(vgpu);
 
-		if (dmlr)
+		if (dmlr) {
 			intel_vgpu_reset_cfg_space(vgpu);
+			/* only reset the failsafe mode when dmlr reset */
+			vgpu->failsafe = false;
+			vgpu->pv_notified = false;
+		}
 	}
 
 	vgpu->resetting = false;