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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.5 359/367] KVM: Play nice with read-only memslots when querying host page size
Date:   Mon, 10 Feb 2020 04:34:32 -0800
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From: Sean Christopherson <sean.j.christopherson@intel.com>

[ Upstream commit 42cde48b2d39772dba47e680781a32a6c4b7dc33 ]

Avoid the "writable" check in __gfn_to_hva_many(), which will always fail
on read-only memslots due to gfn_to_hva() assuming writes.  Functionally,
this allows x86 to create large mappings for read-only memslots that
are backed by HugeTLB mappings.

Note, the changelog for commit 05da45583de9 ("KVM: MMU: large page
support") states "If the largepage contains write-protected pages, a
large pte is not used.", but "write-protected" refers to pages that are
temporarily read-only, e.g. read-only memslots didn't even exist at the
time.

Fixes: 4d8b81abc47b ("KVM: introduce readonly memslot")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
[Redone using kvm_vcpu_gfn_to_memslot_prot. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 virt/kvm/kvm_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index cb1a4bbe3b30f..2b3f36df3d855 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1413,7 +1413,7 @@ unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn)
 
 	size = PAGE_SIZE;
 
-	addr = kvm_vcpu_gfn_to_hva(vcpu, gfn);
+	addr = kvm_vcpu_gfn_to_hva_prot(vcpu, gfn, NULL);
 	if (kvm_is_error_hva(addr))
 		return PAGE_SIZE;
 
-- 
2.20.1