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| author | Peter Xu <peterx@redhat.com> | 2020-09-30 21:22:22 -0400 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-11-15 09:49:15 -0500 |
| commit | fb04a1eddb1a65b6588a021bdc132270d5ae48bb (patch) | |
| tree | 0faceb84959c8f1b65f91d51c1bcc0c0a38ece43 /arch/x86/kvm/mmu | |
| parent | 28bd726aa404c0da8fd6852fe69bb4538a103b71 (diff) | |
| download | linux-fb04a1eddb1a65b6588a021bdc132270d5ae48bb.tar.bz2 | |
KVM: X86: Implement ring-based dirty memory tracking
This patch is heavily based on previous work from Lei Cao
<lei.cao@stratus.com> and Paolo Bonzini <pbonzini@redhat.com>. [1]
KVM currently uses large bitmaps to track dirty memory. These bitmaps
are copied to userspace when userspace queries KVM for its dirty page
information. The use of bitmaps is mostly sufficient for live
migration, as large parts of memory are be dirtied from one log-dirty
pass to another. However, in a checkpointing system, the number of
dirty pages is small and in fact it is often bounded---the VM is
paused when it has dirtied a pre-defined number of pages. Traversing a
large, sparsely populated bitmap to find set bits is time-consuming,
as is copying the bitmap to user-space.
A similar issue will be there for live migration when the guest memory
is huge while the page dirty procedure is trivial. In that case for
each dirty sync we need to pull the whole dirty bitmap to userspace
and analyse every bit even if it's mostly zeros.
The preferred data structure for above scenarios is a dense list of
guest frame numbers (GFN). This patch series stores the dirty list in
kernel memory that can be memory mapped into userspace to allow speedy
harvesting.
This patch enables dirty ring for X86 only. However it should be
easily extended to other archs as well.
[1] https://patchwork.kernel.org/patch/10471409/
Signed-off-by: Lei Cao <lei.cao@stratus.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20201001012222.5767-1-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/mmu')
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 8 | ||||
| -rw-r--r-- | arch/x86/kvm/mmu/tdp_mmu.c | 2 |
2 files changed, 9 insertions, 1 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 5bb1939b65d8..12e5cfe0995e 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1289,6 +1289,14 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm, kvm_mmu_write_protect_pt_masked(kvm, slot, gfn_offset, mask); } +int kvm_cpu_dirty_log_size(void) +{ + if (kvm_x86_ops.cpu_dirty_log_size) + return kvm_x86_ops.cpu_dirty_log_size(); + + return 0; +} + bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm, struct kvm_memory_slot *slot, u64 gfn) { diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index ff28a5c6abd6..cffa51c6049e 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -185,7 +185,7 @@ static void handle_changed_spte_dirty_log(struct kvm *kvm, int as_id, gfn_t gfn, if ((!is_writable_pte(old_spte) || pfn_changed) && is_writable_pte(new_spte)) { slot = __gfn_to_memslot(__kvm_memslots(kvm, as_id), gfn); - mark_page_dirty_in_slot(slot, gfn); + mark_page_dirty_in_slot(kvm, slot, gfn); } } |