Re: [PATCH 5/7] KVM: arm64: Add memory_slot_unmaped counter for kvm_stat
From: Marc Zyngier <maz@kernel.org>
Date: 2021-03-23 17:34:57
Also in:
kvmarm
On Fri, 19 Mar 2021 16:17:09 +0000, Yoan Picchi [off-list ref] wrote:
Add a counter for when a memory slot is unmapped, meaning that all memory belonging to a specific VM is made available to be mapped for anoother VM.
No. It just means it is unmapped from the guest. The VMM still has the pages.
quoted hunk ↗ jump to hunk
A memory slot is the memory that can be used to hold a guest's pages and can be made available by Qemu for instance. For now the memory slot are only unmapped when a vm restarts. Signed-off-by: Yoan Picchi <redacted> --- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/kvm/guest.c | 1 + arch/arm64/kvm/mmu.c | 1 + 3 files changed, 3 insertions(+)diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index e6967951f..76c81aa79 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h@@ -548,6 +548,7 @@ static inline bool __vcpu_write_sys_reg_to_cpu(u64 val, int reg) struct kvm_vm_stat { ulong remote_tlb_flush; ulong flush_all_cache_lines; + ulong memory_slot_unmaped; ulong cached_page_invalidated; };diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c index d948c3bd2..cd227136e 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c@@ -42,6 +42,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { VCPU_STAT("huge_page_mapped", huge_page_mapped), VM_STAT("remote_tlb_flush", remote_tlb_flush), VM_STAT("flush_all_cache_lines", flush_all_cache_lines), + VM_STAT("memory_slot_unmaped", memory_slot_unmaped), VM_STAT("cached_page_invalidated", cached_page_invalidated), VCPU_STAT("exits", exits), VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 985b048df..1e8aeafc2 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c@@ -419,6 +419,7 @@ static void stage2_unmap_memslot(struct kvm *kvm, phys_addr_t addr = memslot->base_gfn << PAGE_SHIFT; phys_addr_t size = PAGE_SIZE * memslot->npages; hva_t reg_end = hva + size; + kvm->stat.memory_slot_unmaped++;
Why is that a relevant thing to track? You even increment the counter before even checking whether this will unmap anything... :-( M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel