From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Add a flag, KVM_DEBUGREG_AUTO_SWITCHED_GUEST, to skip saving/restoring DRs
irrespective of any other flags. TDX-SEAM unconditionally saves and
restores guest DRs and reset to architectural INIT state on TD exit.
So, KVM needs to save host DRs before TD enter without restoring guest DRs
and restore host DRs after TD exit.
Opportunistically convert the KVM_DEBUGREG_* definitions to use BIT().
Reported-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Co-developed-by: Chao Gao <chao.gao@xxxxxxxxx>
Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 10 ++++++++--
arch/x86/kvm/vmx/tdx.c | 1 +
arch/x86/kvm/x86.c | 11 ++++++++---
3 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 95c2ed8fdcd6..42ddf087fe60 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -603,8 +603,14 @@ struct kvm_pmu {
struct kvm_pmu_ops;
enum {
- KVM_DEBUGREG_BP_ENABLED = 1,
- KVM_DEBUGREG_WONT_EXIT = 2,
+ KVM_DEBUGREG_BP_ENABLED = BIT(0),
+ KVM_DEBUGREG_WONT_EXIT = BIT(1),
+ /*
+ * Guest debug registers (DR0-3 and DR6) are saved/restored by hardware
+ * on exit from or enter to guest. KVM needn't switch them. Because DR7
+ * is cleared on exit from guest, DR7 need to be saved/restored.
+ */
+ KVM_DEBUGREG_AUTO_SWITCH = BIT(2),
};
struct kvm_mtrr_range {
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 259139abb8ba..7465074a919d 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -523,6 +523,7 @@ int tdx_vcpu_create(struct kvm_vcpu *vcpu)
vcpu->arch.efer = EFER_SCE | EFER_LME | EFER_LMA | EFER_NX;
+ vcpu->arch.switch_db_regs = KVM_DEBUGREG_AUTO_SWITCH;
vcpu->arch.cr0_guest_owned_bits = -1ul;
vcpu->arch.cr4_guest_owned_bits = -1ul;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7805987d891d..c7d34b04ccdf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10769,7 +10769,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (vcpu->arch.guest_fpu.xfd_err)
wrmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
- if (unlikely(vcpu->arch.switch_db_regs)) {
+ if (unlikely(vcpu->arch.switch_db_regs & ~KVM_DEBUGREG_AUTO_SWITCH)) {
set_debugreg(0, 7);
set_debugreg(vcpu->arch.eff_db[0], 0);
set_debugreg(vcpu->arch.eff_db[1], 1);
@@ -10815,6 +10815,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
*/
if (unlikely(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT)) {
WARN_ON(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP);
+ WARN_ON(vcpu->arch.switch_db_regs & KVM_DEBUGREG_AUTO_SWITCH);
static_call(kvm_x86_sync_dirty_debug_regs)(vcpu);
kvm_update_dr0123(vcpu);
kvm_update_dr7(vcpu);
@@ -10827,8 +10828,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
* care about the messed up debug address registers. But if
* we have some of them active, restore the old state.
*/
- if (hw_breakpoint_active())
- hw_breakpoint_restore();
+ if (hw_breakpoint_active()) {
+ if (!(vcpu->arch.switch_db_regs & KVM_DEBUGREG_AUTO_SWITCH))
+ hw_breakpoint_restore();
+ else
+ set_debugreg(__this_cpu_read(cpu_dr7), 7);
+ }
vcpu->arch.last_vmentry_cpu = vcpu->cpu;
vcpu->arch.last_guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc());
--
2.25.1
