d1785c00474a8aad5253bafdff2832645e6fe95aafe45017e6a31cb6.patch

From 45e19cfe9e152b9bb4140a9dc59cb0b31dd6705b Mon Sep 17 00:00:00 2001
From: David Stevens <stevensd@chromium.org>
Date: Fri, 25 Jun 2021 16:36:16 +0900
Subject: [PATCH] FROMLIST: KVM: mmu: remove over-aggressive warnings

Remove two warnings that require ref counts for pages to be non-zero, as
mapped pfns from follow_pfn may not have an initialized ref count.

Signed-off-by: David Stevens <stevensd@chromium.org>
(am from https://lore.kernel.org/patchwork/patch/1451588/)
(also found at https://lore.kernel.org/r/20210625073616.2184426-6-stevensd@google.com)

BUG=b:184929592, b:176387875
TEST=tast run zork arc.VideoDecodeAccel.vp9_vm

Change-Id: I81a0f12d881470eb469f0c83aecb1b03b74afcaf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3002595
Tested-by: David Stevens <stevensd@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Suleiman Souhlal <suleiman@chromium.org>
Commit-Queue: David Stevens <stevensd@chromium.org>
---
 arch/x86/kvm/mmu/mmu.c | 10 ----------
 virt/kvm/kvm_main.c    |  2 +-
 2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 1ccb769f62af35b2c65f6d23905555263373ade7..f36cd287c195985f9af9fe2784eab818bffdd68b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -534,7 +534,6 @@ static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep)
 	kvm_pfn_t pfn;
 	u64 old_spte = *sptep;
 	int level = sptep_to_sp(sptep)->role.level;
-	struct page *page;
 
 	if (!is_shadow_present_pte(old_spte) ||
 	    !spte_has_volatile_bits(old_spte))
@@ -549,15 +548,6 @@ static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep)
 
 	pfn = spte_to_pfn(old_spte);
 
-	/*
-	 * KVM doesn't hold a reference to any pages mapped into the guest, and
-	 * instead uses the mmu_notifier to ensure that KVM unmaps any pages
-	 * before they are reclaimed.  Sanity check that, if the pfn is backed
-	 * by a refcounted page, the refcount is elevated.
-	 */
-	page = kvm_pfn_to_refcounted_page(pfn);
-	WARN_ON(page && !page_count(page));
-
 	if (is_accessed_spte(old_spte))
 		kvm_set_pfn_accessed(pfn);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 25d7872b29c17ee554eff1f3b5702a33b17a4143..8cf297452c3ed954801bbdcc23010e94ea965fb9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -176,7 +176,7 @@ bool kvm_is_zone_device_page(struct page *page)
 	 * the device has been pinned, e.g. by get_user_pages().  WARN if the
 	 * page_count() is zero to help detect bad usage of this helper.
 	 */
-	if (WARN_ON_ONCE(!page_count(page)))
+	if (!page_count(page))
 		return false;
 
 	return is_zone_device_page(page);
-- 
2.38.1.584.g0f3c55d4c2-goog