[PATCH v2 02/16] KVM: arm64: Provide the host_stage2_try() helper macro

Quentin Perret
2021-07-26T09:29:22Z

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@google.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