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From:   David Brazdil <dbrazdil@google.com>
To:     kvmarm@lists.cs.columbia.edu
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
        James Morse <james.morse@arm.com>,
        Julien Thierry <julien.thierry.kdev@gmail.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        kernel-team@android.com, David Brazdil <dbrazdil@google.com>
Subject: [PATCH v3 09/11] kvm: arm64: Mark hyp stack pages reserved
Date:   Wed, 16 Sep 2020 18:34:37 +0100
Message-Id: <20200916173439.32265-10-dbrazdil@google.com>
In-Reply-To: <20200916173439.32265-1-dbrazdil@google.com>
References: <20200916173439.32265-1-dbrazdil@google.com>
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In preparation for unmapping hyp pages from host stage-2, allocate/free hyp
stack using new helpers which automatically mark the pages reserved.

Signed-off-by: David Brazdil <dbrazdil@google.com>
---
 arch/arm64/kvm/arm.c | 49 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 7af9809fa193..58d7d614519b 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1456,13 +1456,58 @@ static int init_subsystems(void)
 	return err;
 }
 
+/*
+ * Alloc pages and mark them reserved so the kernel never tries to
+ * take them away from the hypervisor.
+ */
+static unsigned long alloc_hyp_pages(gfp_t flags, unsigned int order)
+{
+	struct page *page;
+	unsigned long i;
+
+	page = alloc_pages(flags, order);
+	if (!page)
+		return 0;
+
+	for (i = 0; i < (1ul << order); ++i)
+		mark_page_reserved(page + i);
+
+	return (unsigned long)page_address(page);
+}
+
+static unsigned long alloc_hyp_page(gfp_t flags)
+{
+	return alloc_hyp_pages(flags, 0);
+}
+
+/*
+ * Free pages which were previously marked reserved for the hypervisor.
+ */
+static void free_hyp_pages(unsigned long addr, unsigned int order)
+{
+	unsigned long i;
+	struct page *page;
+
+	if (!addr)
+		return;
+
+	page = virt_to_page(addr);
+	for (i = 0; i < (1ul << order); ++i)
+		free_reserved_page(page + i);
+}
+
+static void free_hyp_page(unsigned long addr)
+{
+	return free_hyp_pages(addr, 0);
+}
+
 static void teardown_hyp_mode(void)
 {
 	int cpu;
 
 	free_hyp_pgds();
 	for_each_possible_cpu(cpu)
-		free_page(per_cpu(kvm_arm_hyp_stack_page, cpu));
+		free_hyp_page(per_cpu(kvm_arm_hyp_stack_page, cpu));
 }
 
 /**
@@ -1486,7 +1531,7 @@ static int init_hyp_mode(void)
 	for_each_possible_cpu(cpu) {
 		unsigned long stack_page;
 
-		stack_page = __get_free_page(GFP_KERNEL);
+		stack_page = alloc_hyp_page(GFP_KERNEL);
 		if (!stack_page) {
 			err = -ENOMEM;
 			goto out_err;
-- 
2.28.0.618.gf4bc123cb7-goog