linux-kernel - [PATCH 06/10] KVM: Don't WARN if kvm_pfn_to

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Date:   Fri, 29 Apr 2022 01:04:12 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 06/10] KVM: Don't WARN if kvm_pfn_to_page() encounters a
 "reserved" pfn

Drop a WARN_ON() if kvm_pfn_to_page() encounters a "reserved" pfn, which
in this context means a struct page that has PG_reserved but is not a/the
ZERO_PAGE and is not a ZONE_DEVICE page.  The usage, via gfn_to_page(),
in x86 is safe as gfn_to_page() is used only to retrieve a page from
KVM-controlled memslot, but the usage in PPC and s390 operates on
arbitrary gfns and thus memslots that can be backed by incompatible
memory.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 virt/kvm/kvm_main.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ab7549195c68..a987188a426f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2703,10 +2703,8 @@ static struct page *kvm_pfn_to_page(kvm_pfn_t pfn)
 	if (is_error_noslot_pfn(pfn))
 		return KVM_ERR_PTR_BAD_PAGE;
 
-	if (kvm_is_reserved_pfn(pfn)) {
-		WARN_ON(1);
+	if (kvm_is_reserved_pfn(pfn))
 		return KVM_ERR_PTR_BAD_PAGE;
-	}
 
 	return pfn_to_page(pfn);
 }
-- 
2.36.0.464.gb9c8b46e94-goog