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Subject[PATCH v2 08/10] kvm: arm64: Mark hyp stack pages reserved
Date
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 d437052c5481..8a1fcf4dffca 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1453,13 +1453,58 @@ 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));
}

/**
@@ -1483,7 +1528,7 @@ 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;
--
2.28.0.402.g5ffc5be6b7-goog
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