[PATCH 039/104] KVM: kvm_vm_ioctl_get_dirty_log restore "nothing dirty" optimization | KernelTrap

[PATCH 039/104] KVM: kvm_vm_ioctl_get_dirty_log restore "nothing dirty" optimization

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From: Avi Kivity <avi@...>

To: <kvm-devel@...>

Cc: <linux-kernel@...>, Rusty Russell <rusty@...>

Subject: [PATCH 039/104] KVM: kvm_vm_ioctl_get_dirty_log restore "nothing dirty" optimization

Date: Monday, September 17, 2007 - 4:31 am

From: Rusty Russell <rusty@rustcorp.com.au>

kvm_vm_ioctl_get_dirty_log scans bitmap to see it it's all zero, but
doesn't use that information.

Avi says:
	Looks like it was used to guard	kvm_mmu_slot_remove_write_access();
	optimizing the case where the guest just leaves the screen alone (which
	it usually does, especially in benchmarks).

	I'd rather reinstate that optimization.  See
	90cb0529dd230548a7f0d6b315997be854caea1b where the damage was done.

It's pretty simple: if the bitmap is all zero, we don't need to do anything to
clean it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---
 drivers/kvm/kvm_main.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index bfb1b6d..5dee302 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -803,11 +803,14 @@ static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 	if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n))
 		goto out;
 
-	mutex_lock(&kvm->lock);
-	kvm_mmu_slot_remove_write_access(kvm, log->slot);
-	kvm_flush_remote_tlbs(kvm);
-	memset(memslot->dirty_bitmap, 0, n);
-	mutex_unlock(&kvm->lock);
+	/* If nothing is dirty, don't bother messing with page tables. */
+	if (any) {
+		mutex_lock(&kvm->lock);
+		kvm_mmu_slot_remove_write_access(kvm, log->slot);
+		kvm_flush_remote_tlbs(kvm);
+		memset(memslot->dirty_bitmap, 0, n);
+		mutex_unlock(&kvm->lock);
+	}
 
 	r = 0;
 
-- 
1.5.3

-
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Messages in current thread:

[PATCH 000/104] KVM patch queue for the 2.6.24 merge window, Avi Kivity, (Mon Sep 17, 4:30 am)

git-send-email creates duplicate Message-Id's, Adrian Bunk, (Mon Sep 17, 11:59 am)

Re: git-send-email creates duplicate Message-Id's, Junio C Hamano, (Mon Sep 17, 4:22 pm)

Re: git-send-email creates duplicate Message-Id's, Matti Aarnio, (Mon Sep 17, 4:47 pm)

[PATCH 008/104] KVM: Trivial: Comment spelling may escape grep, Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 011/104] KVM: Use standard CR3 flags, tighten checking, Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 014/104] KVM: Set exit_reason to KVM_EXIT_MMIO where ..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 012/104] KVM: Use standard CR4 flags, tighten checking, Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 015/104] KVM: Use standard CR8 flags, and fix TPR def..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 018/104] KVM: Return if the pdptrs are invalid when t..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 023/104] KVM: load_pdptrs() cleanups, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 021/104] KVM: VMX: Import some constants of vmcs from..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 016/104] KVM: x86 emulator: fix cmov for writeback ch..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 026/104] KVM: VMX: Improve the method of writing vmcs..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 029/104] KVM: Convert vm lock to a mutex, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 035/104] KVM: Change the emulator_{read,write,cmpxchg..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 043/104] KVM: SVM: Make set_msr_interception more rel..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 024/104] KVM: Remove arch specific components from th..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 044/104] KVM: Remove redundant alloc_vmcs_cpu declara..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 028/104] KVM: Use the scheduler preemption notifiers ..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 036/104] KVM: Remove kvm_{read,write}_guest(), Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 046/104] KVM: Remove stat_set from debugfs, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 031/104] KVM: VMX: pass vcpu_vmx internally, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 050/104] KVM: VMX: Remove a duplicated ia32e mode vm ..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 055/104] KVM: Communicate cr8 changes to userspace, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 057/104] KVM: x86 emulator: implement 'jmp rel' instr..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 056/104] KVM: x86 emulator: implement 'and $imm, %{al..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 059/104] KVM: x86 emulator: implement 'push reg' (opc..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 052/104] KVM: Cleanup string I/O instruction emulation, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 062/104] KVM: X86 emulator: fix 'push reg' writeback, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 074/104] KVM: pending irq save/restore, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 082/104] KVM: Set the ET flag in CR0 after initializi..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 084/104] KVM: Clean up unloved invlpg emulation, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 083/104] KVM: Remove the unused invlpg member of stru..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 081/104] KVM: enable in-kernel APIC INIT/SIPI handling, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 085/104] KVM: Keep control regs in sync, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 086/104] KVM: Hoist SVM's get_cs_db_l_bits into core ..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 091/104] KVM: Move main vcpu loop into subarch indepe..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 092/104] KVM: VMX: Fix exit qualification width on i386, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 093/104] KVM: x86 emulator: push imm8, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 094/104] KVM: x86 emulator: call near, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 095/104] KVM: x86 emulator: pushf, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 096/104] KVM: Improve emulation failure reporting, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 097/104] KVM: x86 emulator: sort opcodes into ascendi..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 103/104] KVM: x86 emulator: popf, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 099/104] KVM: X86 emulator: jump conditional short, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 102/104] KVM: x86 emulator: fix src, dst value initia..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 088/104] KVM: Rename kvm_arch_ops to kvm_x86_ops, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 098/104] KVM: x86 emulator: imlpement jump conditiona..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 100/104] KVM: x86 emulator: lea, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 101/104] KVM: x86 emulator: jmp abs, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 090/104] KVM: VMX: Move vm entry failure handling to ..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 087/104] KVM: Simplify memory allocation, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 089/104] KVM: MMU: Don't do GFP_NOWAIT allocations, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 080/104] KVM: round robin for APIC lowest priority de..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 076/104] KVM: Keep track of missed timer irq injections, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 079/104] KVM: deliver PIC interrupt only to vcpu0, Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 075/104] KVM: VMX: Use shadow TPR/cr8 for 64-bits gue..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 066/104] KVM: Emulate local APIC in kernel, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 078/104] KVM: disable tpr/cr8 sync when in-kernel API..., Avi Kivity, (Mon Sep 17, 4:32 am)

[PATCH 077/104] KVM: Migrate lapic hrtimer when vcpu moves t..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 061/104] KVM: Support more memory slots, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 063/104] KVM: VMX: Split segments reload in vmx_load_..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 060/104] KVM: VMX: allow rmode_tss_base() to work wit..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 072/104] KVM: in-kernel IOAPIC save and restore support, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 067/104] KVM: In-kernel I/O APIC model, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 073/104] KVM: in-kernel LAPIC save and restore support, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 064/104] KVM: Add support for in-kernel PIC emulation, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 070/104] KVM: Add get/set irqchip ioctls for in-kerne..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 071/104] KVM: Bypass irq_pending get/set when using i..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 068/104] KVM: Emulate hlt in the kernel, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 065/104] KVM: Define and use cr8 access functions, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 069/104] KVM: Protect in-kernel pio using kvm->lock, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 058/104] KVM: x86 emulator: Implement 'jmp rel short'..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 034/104] KVM: SVM: internal function name cleanup, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 025/104] KVM: Dynamically allocate vcpus, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 053/104] KVM: Clean up kvm_setup_pio(), Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 051/104] KVM: Remove useless assignment, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 048/104] KVM: Add and use pr_unimpl for standard form..., Avi Kivity, (Mon Sep 17, 4:31 am)

Re: [PATCH 048/104] KVM: Add and use pr_unimpl for standard ..., Joe Perches, (Mon Sep 17, 12:16 pm)

Re: [PATCH 048/104] KVM: Add and use pr_unimpl for standard ..., Rusty Russell, (Mon Sep 17, 7:08 pm)

[PATCH 049/104] KVM: Use kmem_cache_free for kmem_cache_zall..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 033/104] KVM: SVM: de-containization, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 047/104] KVM: Remove unneeded kvm_dev_open and kvm_de..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 045/104] KVM: Fix defined but not used warning in dri..., Avi Kivity, (Mon Sep 17, 4:31 am)

Re: [PATCH 045/104] KVM: Fix defined but not used warning in..., David Miller, (Mon Sep 17, 12:27 pm)

Re: [kvm-devel] [PATCH 045/104] KVM: Fix defined but not use..., Avi Kivity, (Mon Sep 17, 1:35 pm)

[PATCH 037/104] KVM: Use kmem cache for allocating vcpus, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 038/104] KVM: Use alignment properties of vcpu to sim..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 040/104] KVM: VMX: Add cpu consistency check, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 042/104] KVM: Cleanup mark_page_dirty, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 039/104] KVM: kvm_vm_ioctl_get_dirty_log restore "not..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 030/104] KVM: fx_init() needs preemption disabled whi..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 041/104] KVM: Don't assign vcpu->cr3 if it's inval..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 020/104] KVM: Move gfn_to_page out of kmap/unmap pairs, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 032/104] KVM: Remove three magic numbers, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 022/104] KVM: Remove dead code in the cmpxchg instruc..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 027/104] KVM: add hypercall nr to kvm_run, Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 019/104] KVM: Hoist kvm_mmu_reload() out of the criti..., Avi Kivity, (Mon Sep 17, 4:31 am)

[PATCH 017/104] KVM: x86 emulator: fix faulty check for two-..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 010/104] KVM: Trivial: Use standard CR0 flags macros ..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 013/104] KVM: Trivial: Use standard BITMAP macros, op..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 009/104] KVM: Trivial: Avoid hardware_disable predecl..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 006/104] KVM: Trivial: Remove unused struct cpu_user_..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 007/104] KVM: Trivial: Make decode_register() static, Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 005/104] KVM: Trivial: /dev/kvm interface is no longe..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 004/104] KVM: In-kernel string pio write support, Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 003/104] KVM: Future-proof the exit information union..., Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 002/104] KVM: SMP: Add vcpu_id field in struct vcpu, Avi Kivity, (Mon Sep 17, 4:30 am)

[PATCH 001/104] KVM: Fix *nopage() in kvm_main.c, Avi Kivity, (Mon Sep 17, 4:30 am)

Re: [PATCH 001/104] KVM: Fix *nopage() in kvm_main.c, Christoph Hellwig, (Mon Sep 17, 5:13 am)

Re: [PATCH 001/104] KVM: Fix *nopage() in kvm_main.c, Avi Kivity, (Mon Sep 17, 5:15 am)

Re: [PATCH 001/104] KVM: Fix *nopage() in kvm_main.c, Avi Kivity, (Mon Sep 17, 5:18 am)

Re: [PATCH 001/104] KVM: Fix *nopage() in kvm_main.c, Nick Piggin, (Sun Sep 16, 5:29 pm)

Re: [PATCH 001/104] KVM: Fix *nopage() in kvm_main.c, Avi Kivity, (Mon Sep 17, 2:19 pm)

Re: [PATCH 001/104] KVM: Fix *nopage() in kvm_main.c, Nick Piggin, (Mon Sep 17, 1:17 pm)

Re: [PATCH 001/104] KVM: Fix *nopage() in kvm_main.c, Avi Kivity, (Tue Sep 18, 6:44 am)

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