Thread (23 messages) 23 messages, 2 authors, 2021-07-28

Re: [PATCH v2 04/16] KVM: arm64: Optimize host memory aborts

From: Marc Zyngier <maz@kernel.org>
Date: 2021-07-26 13:24:48
Also in: kvmarm, lkml

On Mon, 26 Jul 2021 14:13:06 +0100,
Quentin Perret [off-list ref] wrote:
On Monday 26 Jul 2021 at 11:35:10 (+0100), Marc Zyngier wrote:
[...]
quoted hunk ↗ jump to hunk
quoted
You could also use a kvm_mem_range for the iteration, and add a helper
that checks for the inclusion.
Something like this (untested)?
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 75273166d2c5..07d228163090 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -234,9 +234,15 @@ static inline int __host_stage2_idmap(u64 start, u64 end,
                __ret;                                                  \
         })

+static inline bool range_included(struct kvm_mem_range *child,
+                                 struct kvm_mem_range *parent)
+{
+       return parent->start <= child->start && child->end <= parent->end;
+}
+
 static int host_stage2_find_range(u64 addr, struct kvm_mem_range *range)
 {
-       u64 granule, start, end;
+       struct kvm_mem_range cur;
        kvm_pte_t pte;
        u32 level;
        int ret;
@@ -252,16 +258,15 @@ static int host_stage2_find_range(u64 addr, struct kvm_mem_range *range)
                return -EPERM;

        do {
-               granule = kvm_granule_size(level);
-               start = ALIGN_DOWN(addr, granule);
-               end = start + granule;
+               u64 granule = kvm_granule_size(level);
+               cur.start = ALIGN_DOWN(addr, granule);
+               cur.end = cur.start + granule;
                level++;
        } while ((level < KVM_PGTABLE_MAX_LEVELS) &&
-                       (!kvm_level_supports_block_mapping(level) ||
-                        start < range->start || range->end < end));
+                       !(kvm_level_supports_block_mapping(level) &&
+                         range_included(&cur, parent)));

-       range->start = start;
-       range->end = end;
+       *range = cur;

        return 0;
 }
Beautiful.

	M.

-- 
Without deviation from the norm, progress is not possible.

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