linux-kernel - [PATCH 08/27] drm/i915/gvt: Hoist acquisition of vgpu_lock out to kvmgt_page_track

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Message-ID: <20221223005739.1295925-9-seanjc@google.com>
Date:   Fri, 23 Dec 2022 00:57:20 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>
Cc:     kvm@...r.kernel.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yan Zhao <yan.y.zhao@...el.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 08/27] drm/i915/gvt: Hoist acquisition of vgpu_lock out to kvmgt_page_track_write()

Host the acquisition of vgpu_lock from intel_vgpu_page_track_handler() out
to its sole caller, kvmgt_page_track_write().  An upcoming fix will add a
mutex to protect the gfn hash table that referenced by
kvmgt_gfn_is_write_protected(), i.e. kvmgt_page_track_write() will need to
acquire another lock.  Conceptually, the to-be-introduced gfn_lock has
finer granularity than vgpu_lock and so the lock order should ideally be
vgpu_lock => gfn_lock, e.g. to avoid potential lock inversion elsewhere in
KVMGT.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 drivers/gpu/drm/i915/gvt/kvmgt.c      |  4 ++++
 drivers/gpu/drm/i915/gvt/page_track.c | 10 ++--------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 5d0e029d60d7..ca9926061cd8 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1626,9 +1626,13 @@ static void kvmgt_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa,
 	struct intel_vgpu *info =
 		container_of(node, struct intel_vgpu, track_node);
 
+	mutex_lock(&info->vgpu_lock);
+
 	if (kvmgt_gfn_is_write_protected(info, gpa_to_gfn(gpa)))
 		intel_vgpu_page_track_handler(info, gpa,
 						     (void *)val, len);
+
+	mutex_unlock(&info->vgpu_lock);
 }
 
 static void kvmgt_page_track_flush_slot(struct kvm *kvm,
diff --git a/drivers/gpu/drm/i915/gvt/page_track.c b/drivers/gpu/drm/i915/gvt/page_track.c
index 3375b51c75f1..6d72d11914a5 100644
--- a/drivers/gpu/drm/i915/gvt/page_track.c
+++ b/drivers/gpu/drm/i915/gvt/page_track.c
@@ -162,13 +162,9 @@ int intel_vgpu_page_track_handler(struct intel_vgpu *vgpu, u64 gpa,
 	struct intel_vgpu_page_track *page_track;
 	int ret = 0;
 
-	mutex_lock(&vgpu->vgpu_lock);
-
 	page_track = intel_vgpu_find_page_track(vgpu, gpa >> PAGE_SHIFT);
-	if (!page_track) {
-		ret = -ENXIO;
-		goto out;
-	}
+	if (!page_track)
+		return -ENXIO;
 
 	if (unlikely(vgpu->failsafe)) {
 		/* Remove write protection to prevent furture traps. */
@@ -179,7 +175,5 @@ int intel_vgpu_page_track_handler(struct intel_vgpu *vgpu, u64 gpa,
 			gvt_err("guest page write error, gpa %llx\n", gpa);
 	}
 
-out:
-	mutex_unlock(&vgpu->vgpu_lock);
 	return ret;
 }
-- 
2.39.0.314.g84b9a713c41-goog