diff options
author | Jing Liu <jing2.liu@intel.com> | 2022-01-05 04:35:23 -0800 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-01-14 13:44:18 -0500 |
commit | ec5be88ab29fd9145c7ced20b58fb96f7c6b6890 (patch) | |
tree | 06aec550f4d361a24e520c8a60cd1b8a25630fa7 /arch/x86/kvm/vmx/vmx.c | |
parent | 1df4fd834e8e2c00973ac2003ad0e6feb8750b31 (diff) | |
download | linux-ec5be88ab29fd9145c7ced20b58fb96f7c6b6890.tar.bz2 |
kvm: x86: Intercept #NM for saving IA32_XFD_ERR
Guest IA32_XFD_ERR is generally modified in two places:
- Set by CPU when #NM is triggered;
- Cleared by guest in its #NM handler;
Intercept #NM for the first case when a nonzero value is written
to IA32_XFD. Nonzero indicates that the guest is willing to do
dynamic fpstate expansion for certain xfeatures, thus KVM needs to
manage and virtualize guest XFD_ERR properly. The vcpu exception
bitmap is updated in XFD write emulation according to guest_fpu::xfd.
Save the current XFD_ERR value to the guest_fpu container in the #NM
VM-exit handler. This must be done with interrupt disabled, otherwise
the unsaved MSR value may be clobbered by host activity.
The saving operation is conducted conditionally only when guest_fpu:xfd
includes a non-zero value. Doing so also avoids misread on a platform
which doesn't support XFD but #NM is triggered due to L1 interception.
Queueing #NM to the guest is postponed to handle_exception_nmi(). This
goes through the nested_vmx check so a virtual vmexit is queued instead
when #NM is triggered in L2 but L1 wants to intercept it.
Restore the host value (always ZERO outside of the host #NM
handler) before enabling interrupt.
Restore the guest value from the guest_fpu container right before
entering the guest (with interrupt disabled).
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20220105123532.12586-13-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx/vmx.c')
-rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 7b5abe25e1e5..84f6904cdb6e 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -36,6 +36,7 @@ #include <asm/debugreg.h> #include <asm/desc.h> #include <asm/fpu/api.h> +#include <asm/fpu/xstate.h> #include <asm/idtentry.h> #include <asm/io.h> #include <asm/irq_remapping.h> @@ -761,6 +762,13 @@ void vmx_update_exception_bitmap(struct kvm_vcpu *vcpu) vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, match); } + /* + * Trap #NM if guest xfd contains a non-zero value so guest XFD_ERR + * can be saved timely. + */ + if (vcpu->arch.guest_fpu.fpstate->xfd) + eb |= (1u << NM_VECTOR); + vmcs_write32(EXCEPTION_BITMAP, eb); } @@ -1967,6 +1975,12 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_KERNEL_GS_BASE: vmx_write_guest_kernel_gs_base(vmx, data); break; + case MSR_IA32_XFD: + ret = kvm_set_msr_common(vcpu, msr_info); + /* Update #NM interception according to guest xfd */ + if (!ret) + vmx_update_exception_bitmap(vcpu); + break; #endif case MSR_IA32_SYSENTER_CS: if (is_guest_mode(vcpu)) @@ -4798,6 +4812,17 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) if (is_machine_check(intr_info) || is_nmi(intr_info)) return 1; /* handled by handle_exception_nmi_irqoff() */ + /* + * Queue the exception here instead of in handle_nm_fault_irqoff(). + * This ensures the nested_vmx check is not skipped so vmexit can + * be reflected to L1 (when it intercepts #NM) before reaching this + * point. + */ + if (is_nm_fault(intr_info)) { + kvm_queue_exception(vcpu, NM_VECTOR); + return 1; + } + if (is_invalid_opcode(intr_info)) return handle_ud(vcpu); @@ -6399,6 +6424,26 @@ static void handle_interrupt_nmi_irqoff(struct kvm_vcpu *vcpu, kvm_after_interrupt(vcpu); } +static void handle_nm_fault_irqoff(struct kvm_vcpu *vcpu) +{ + /* + * Save xfd_err to guest_fpu before interrupt is enabled, so the + * MSR value is not clobbered by the host activity before the guest + * has chance to consume it. + * + * Do not blindly read xfd_err here, since this exception might + * be caused by L1 interception on a platform which doesn't + * support xfd at all. + * + * Do it conditionally upon guest_fpu::xfd. xfd_err matters + * only when xfd contains a non-zero value. + * + * Queuing exception is done in vmx_handle_exit. See comment there. + */ + if (vcpu->arch.guest_fpu.fpstate->xfd) + rdmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err); +} + static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx) { const unsigned long nmi_entry = (unsigned long)asm_exc_nmi_noist; @@ -6407,6 +6452,9 @@ static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx) /* if exit due to PF check for async PF */ if (is_page_fault(intr_info)) vmx->vcpu.arch.apf.host_apf_flags = kvm_read_and_reset_apf_flags(); + /* if exit due to NM, handle before interrupts are enabled */ + else if (is_nm_fault(intr_info)) + handle_nm_fault_irqoff(&vmx->vcpu); /* Handle machine checks before interrupts are enabled */ else if (is_machine_check(intr_info)) kvm_machine_check(); |