diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2014-02-21 10:32:27 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2014-03-11 10:46:03 +0100 |
| commit | 81908bf44340eb5ebc9969f67e6c8be0c92f2857 (patch) | |
| tree | 67fb9e8f536d8319c54f9e6af1d6cbaf844e6673 /arch/x86 | |
| parent | c77fb5fe6f031bee9403397ae7b94ea22ea19aa7 (diff) | |
| download | op-kernel-dev-81908bf44340eb5ebc9969f67e6c8be0c92f2857.zip op-kernel-dev-81908bf44340eb5ebc9969f67e6c8be0c92f2857.tar.gz | |
KVM: vmx: Allow the guest to run with dirty debug registers
When not running in guest-debug mode (i.e. the guest controls the debug
registers, having to take an exit for each DR access is a waste of time.
If the guest gets into a state where each context switch causes DR to be
saved and restored, this can take away as much as 40% of the execution
time from the guest.
If the guest is running with vcpu->arch.db == vcpu->arch.eff_db, we
can let it write freely to the debug registers and reload them on the
next exit. We still need to exit on the first access, so that the
KVM_DEBUGREG_WONT_EXIT flag is set in switch_db_regs; after that, further
accesses to the debug registers will not cause a vmexit.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/vmx.c | 38 |
1 files changed, 37 insertions, 1 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index b2a913b..a9940ec 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -43,6 +43,7 @@ #include <asm/i387.h> #include <asm/xcr.h> #include <asm/perf_event.h> +#include <asm/debugreg.h> #include <asm/kexec.h> #include "trace.h" @@ -2850,7 +2851,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf) vmx_capability.ept, vmx_capability.vpid); } - min = 0; + min = VM_EXIT_SAVE_DEBUG_CONTROLS; #ifdef CONFIG_X86_64 min |= VM_EXIT_HOST_ADDR_SPACE_SIZE; #endif @@ -5084,6 +5085,22 @@ static int handle_dr(struct kvm_vcpu *vcpu) } } + if (vcpu->guest_debug == 0) { + u32 cpu_based_vm_exec_control; + + cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL); + cpu_based_vm_exec_control &= ~CPU_BASED_MOV_DR_EXITING; + vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control); + + /* + * No more DR vmexits; force a reload of the debug registers + * and reenter on this instruction. The next vmexit will + * retrieve the full state of the debug registers. + */ + vcpu->arch.switch_db_regs |= KVM_DEBUGREG_WONT_EXIT; + return 1; + } + exit_qualification = vmcs_readl(EXIT_QUALIFICATION); dr = exit_qualification & DEBUG_REG_ACCESS_NUM; reg = DEBUG_REG_ACCESS_REG(exit_qualification); @@ -5110,6 +5127,24 @@ static void vmx_set_dr6(struct kvm_vcpu *vcpu, unsigned long val) { } +static void vmx_sync_dirty_debug_regs(struct kvm_vcpu *vcpu) +{ + u32 cpu_based_vm_exec_control; + + get_debugreg(vcpu->arch.db[0], 0); + get_debugreg(vcpu->arch.db[1], 1); + get_debugreg(vcpu->arch.db[2], 2); + get_debugreg(vcpu->arch.db[3], 3); + get_debugreg(vcpu->arch.dr6, 6); + vcpu->arch.dr7 = vmcs_readl(GUEST_DR7); + + vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_WONT_EXIT; + + cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL); + cpu_based_vm_exec_control |= CPU_BASED_MOV_DR_EXITING; + vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control); +} + static void vmx_set_dr7(struct kvm_vcpu *vcpu, unsigned long val) { vmcs_writel(GUEST_DR7, val); @@ -8628,6 +8663,7 @@ static struct kvm_x86_ops vmx_x86_ops = { .get_dr6 = vmx_get_dr6, .set_dr6 = vmx_set_dr6, .set_dr7 = vmx_set_dr7, + .sync_dirty_debug_regs = vmx_sync_dirty_debug_regs, .cache_reg = vmx_cache_reg, .get_rflags = vmx_get_rflags, .set_rflags = vmx_set_rflags, |
