Re: [PATCH v3 05/27] KVM: VMX: Disable FRED if FRED consistency checks fail

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On 10/22/2024 1:48 AM, Chao Gao wrote:
On Mon, Sep 30, 2024 at 10:00:48PM -0700, Xin Li (Intel) wrote:
From: Xin Li <xin3.li@xxxxxxxxx>

Do not virtualize FRED if FRED consistency checks fail.

Either on broken hardware, or when run KVM on top of another hypervisor
before the underlying hypervisor implements nested FRED correctly.

Suggested-by: Chao Gao <chao.gao@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>

Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>

one nit below,

---
arch/x86/kvm/vmx/capabilities.h | 7 +++++++
arch/x86/kvm/vmx/vmx.c          | 3 +++
2 files changed, 10 insertions(+)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index e8f3ad0f79ee..2962a3bb9747 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -400,6 +400,13 @@ static inline bool vmx_pebs_supported(void)
	return boot_cpu_has(X86_FEATURE_PEBS) && kvm_pmu_cap.pebs_ept;
}

+static inline bool cpu_has_vmx_fred(void)
+{
+	/* No need to check FRED VM exit controls. */

how about:

	/*
	 * setup_vmcs_config() guarantees FRED VM-entry/exit controls are
	 * either all set or none. So, no need to check FRED VM-exit controls.
	 */

It is better to call out the reason.


make sense!




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