linux-kernel - [PATCH v2 02/16] KVM: arm64: Provide the host_stage2

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Date:   Mon, 26 Jul 2021 10:28:51 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     maz@...nel.org, james.morse@....com, alexandru.elisei@....com,
        suzuki.poulose@....com, catalin.marinas@....com, will@...nel.org
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, ardb@...nel.org, qwandor@...gle.com,
        tabba@...gle.com, dbrazdil@...gle.com, kernel-team@...roid.com,
        Quentin Perret <qperret@...gle.com>
Subject: [PATCH v2 02/16] KVM: arm64: Provide the host_stage2_try() helper macro

We currently unmap all MMIO mappings from the host stage-2 to recycle
the pages whenever we run out. In order to make this pattern easy to
re-use from other places, factor the logic out into a dedicated macro.
While at it, apply the macro for the kvm_pgtable_stage2_set_owner()
calls. They're currently only called early on and are guaranteed to
succeed, but making them robust to the -ENOMEM case doesn't hurt and
will avoid painful debugging sessions later on.

Signed-off-by: Quentin Perret <qperret@...gle.com>
---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 40 +++++++++++++++------------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index d938ce95d3bd..871149246f5f 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -208,6 +208,25 @@ static inline int __host_stage2_idmap(u64 start, u64 end,
 				      prot, &host_s2_pool);
 }
 
+/*
+ * The pool has been provided with enough pages to cover all of memory with
+ * page granularity, but it is difficult to know how much of the MMIO range
+ * we will need to cover upfront, so we may need to 'recycle' the pages if we
+ * run out.
+ *
+ * Must be called with host_kvm.lock held.
+ */
+#define host_stage2_try(fn, ...)					\
+	({								\
+		int __ret = fn(__VA_ARGS__);				\
+		if (__ret == -ENOMEM) {					\
+			__ret = host_stage2_unmap_dev_all();		\
+			if (!__ret)					\
+				__ret = fn(__VA_ARGS__);		\
+		}							\
+		__ret;							\
+	 })
+
 static int host_stage2_idmap(u64 addr)
 {
 	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W;
@@ -223,22 +242,7 @@ static int host_stage2_idmap(u64 addr)
 	if (ret)
 		goto unlock;
 
-	ret = __host_stage2_idmap(range.start, range.end, prot);
-	if (ret != -ENOMEM)
-		goto unlock;
-
-	/*
-	 * The pool has been provided with enough pages to cover all of memory
-	 * with page granularity, but it is difficult to know how much of the
-	 * MMIO range we will need to cover upfront, so we may need to 'recycle'
-	 * the pages if we run out.
-	 */
-	ret = host_stage2_unmap_dev_all();
-	if (ret)
-		goto unlock;
-
-	ret = __host_stage2_idmap(range.start, range.end, prot);
-
+	ret = host_stage2_try(__host_stage2_idmap, range.start, range.end, prot);
 unlock:
 	hyp_spin_unlock(&host_kvm.lock);
 
@@ -257,8 +261,8 @@ int __pkvm_mark_hyp(phys_addr_t start, phys_addr_t end)
 		return -EINVAL;
 
 	hyp_spin_lock(&host_kvm.lock);
-	ret = kvm_pgtable_stage2_set_owner(&host_kvm.pgt, start, end - start,
-					   &host_s2_pool, pkvm_hyp_id);
+	ret = host_stage2_try(kvm_pgtable_stage2_set_owner, &host_kvm.pgt,
+			      start, end - start, &host_s2_pool, pkvm_hyp_id);
 	hyp_spin_unlock(&host_kvm.lock);
 
 	return ret != -EAGAIN ? ret : 0;
-- 
2.32.0.432.gabb21c7263-goog