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Date: Wed, 13 Mar 2019 09:15:50 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Fenghua Yu <fenghua.yu@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, H Peter Anvin <hpa@...or.com>,
Dave Hansen <dave.hansen@...el.com>,
Ashok Raj <ashok.raj@...el.com>,
Peter Zijlstra <peterz@...radead.org>,
Xiaoyao Li <xiaoyao.li@...el.com>,
Michael Chan <michael.chan@...adcom.com>,
Ravi V Shankar <ravi.v.shankar@...el.com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>,
linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
kvm@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...ux.intel.com>
Subject: Re: [PATCH v5 11/18] kvm/vmx: Emulate MSR TEST_CTL
On 13/03/19 00:00, Fenghua Yu wrote:
> From: Xiaoyao Li <xiaoyao.li@...ux.intel.com>
>
> A control bit (bit 29) in TEST_CTL MSR 0x33 will be introduced in
> future x86 processors. When bit 29 is set, the processor causes #AC
> exception for split locked accesses at all CPL.
>
> Please check the latest Intel 64 and IA-32 Architectures Software
> Developer's Manual for more detailed information on the MSR and
> the split lock bit.
>
> This patch emulate MSR TEST_CTL with vmx->msr_test_ctl and does the
> following:
> 1. As we emulate MSR TEST_CTL of guest, we should enable the related bits
> in CORE_CAPABILITY to corretly report this feature to guest.
>
> 2. Differentiate MSR TEST_CTL between host and guest.
>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...ux.intel.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 35 +++++++++++++++++++++++++++++++++++
> arch/x86/kvm/vmx/vmx.h | 1 +
> arch/x86/kvm/x86.c | 17 ++++++++++++++++-
> 3 files changed, 52 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 30a6bcd735ec..270c6566fd5a 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1659,6 +1659,12 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> u32 index;
>
> switch (msr_info->index) {
> + case MSR_TEST_CTL:
> + if (!msr_info->host_initiated &&
> + !(vcpu->arch.core_capability & CORE_CAP_SPLIT_LOCK_DETECT))
> + return 1;
> + msr_info->data = vmx->msr_test_ctl;
> + break;
> #ifdef CONFIG_X86_64
> case MSR_FS_BASE:
> msr_info->data = vmcs_readl(GUEST_FS_BASE);
> @@ -1799,6 +1805,14 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> u32 index;
>
> switch (msr_index) {
> + case MSR_TEST_CTL:
> + if (!(vcpu->arch.core_capability & CORE_CAP_SPLIT_LOCK_DETECT))
> + return 1;
> +
> + if (data & ~TEST_CTL_ENABLE_SPLIT_LOCK_DETECT)
> + return 1;
> + vmx->msr_test_ctl = data;
> + break;
> case MSR_EFER:
> ret = kvm_set_msr_common(vcpu, msr_info);
> break;
> @@ -4085,6 +4099,9 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx)
>
> vmx->arch_capabilities = kvm_get_arch_capabilities();
>
> + /* disable AC split lock by default */
> + vmx->msr_test_ctl = 0;
> +
> vm_exit_controls_init(vmx, vmx_vmexit_ctrl());
>
> /* 22.2.1, 20.8.1 */
> @@ -4122,6 +4139,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>
> vmx->rmode.vm86_active = 0;
> vmx->spec_ctrl = 0;
> + vmx->msr_test_ctl = 0;
>
> vcpu->arch.microcode_version = 0x100000000ULL;
> vmx->vcpu.arch.regs[VCPU_REGS_RDX] = get_rdx_init_val();
> @@ -6321,6 +6339,21 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
> msrs[i].host, false);
> }
>
> +static void atomic_switch_msr_test_ctl(struct vcpu_vmx *vmx)
> +{
> + u64 host_msr_test_ctl;
> +
> + /* if TEST_CTL MSR doesn't exist on the hardware, we do nothing */
> + if (rdmsrl_safe(MSR_TEST_CTL, &host_msr_test_ctl))
> + return;
> +
> + if (host_msr_test_ctl == vmx->msr_test_ctl)
> + clear_atomic_switch_msr(vmx, MSR_TEST_CTL);
> + else
> + add_atomic_switch_msr(vmx, MSR_TEST_CTL, vmx->msr_test_ctl,
> + host_msr_test_ctl, false);
> +}
> +
> static void vmx_arm_hv_timer(struct vcpu_vmx *vmx, u32 val)
> {
> vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, val);
> @@ -6562,6 +6595,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
>
> atomic_switch_perf_msrs(vmx);
>
> + atomic_switch_msr_test_ctl(vmx);
> +
> vmx_update_hv_timer(vcpu);
>
> /*
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 0ac0a64c7790..8549cba0fb75 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -191,6 +191,7 @@ struct vcpu_vmx {
> u64 msr_guest_kernel_gs_base;
> #endif
>
> + u64 msr_test_ctl;
> u64 arch_capabilities;
> u64 spec_ctrl;
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e20cbb8c2b74..ad1df965574e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1228,7 +1228,22 @@ EXPORT_SYMBOL_GPL(kvm_get_arch_capabilities);
>
> u64 kvm_get_core_capability(void)
> {
> - return 0;
> + u64 data;
> +
> + rdmsrl_safe(MSR_IA32_CORE_CAPABILITY, &data);
> +
> + /* mask non-virtualizable functions */
> + data &= CORE_CAP_SPLIT_LOCK_DETECT;
> +
> + /*
> + * There will be a list of FMS values that have split lock detection
> + * but lack the CORE CAPABILITY MSR. In this case, we can set
> + * CORE_CAP_SPLIT_LOCK_DETECT since we emulate MSR CORE_CAPABILITY.
> + */
> + if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
> + data |= CORE_CAP_SPLIT_LOCK_DETECT;
> +
> + return data;
> }
> EXPORT_SYMBOL_GPL(kvm_get_core_capability);
>
>
Acked-by: Paolo Bonzini <pbonzini@...hat.com>
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