linux-kernel - [RFC PATCH 47/73] KVM: x86/PVM: Handle the left supported MSRs in msrs_to_save

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Message-Id: <20240226143630.33643-48-jiangshanlai@gmail.com>
Date: Mon, 26 Feb 2024 22:36:04 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>,
	Hou Wenlong <houwenlong.hwl@...group.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...hat.com>,
	kvm@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	x86@...nel.org,
	Kees Cook <keescook@...omium.org>,
	Juergen Gross <jgross@...e.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [RFC PATCH 47/73] KVM: x86/PVM: Handle the left supported MSRs in msrs_to_save_base[]

From: Lai Jiangshan <jiangshan.ljs@...group.com>

The MSR_TSC_AUX is allowed to be modified by the guest to support
RDTSCP/RDPID in the guest. However, the MSR_IA32_FEAT_CTRL is not fully
supported for the guest at this time; only the FEAT_CTL_LOCKED bit is
valid for the guest.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/kvm/pvm/pvm.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/arch/x86/kvm/pvm/pvm.c b/arch/x86/kvm/pvm/pvm.c
index fd3d6f7301af..a32d2728eb02 100644
--- a/arch/x86/kvm/pvm/pvm.c
+++ b/arch/x86/kvm/pvm/pvm.c
@@ -854,6 +854,32 @@ static void pvm_msr_filter_changed(struct kvm_vcpu *vcpu)
 	/* Accesses to MSRs are emulated in hypervisor, nothing to do here. */
 }
 
+static inline bool is_pvm_feature_control_msr_valid(struct vcpu_pvm *pvm,
+						    struct msr_data *msr_info)
+{
+	/*
+	 * currently only FEAT_CTL_LOCKED bit is valid, maybe
+	 * vmx, sgx and mce associated bits can be valid when those features
+	 * are supported for guest.
+	 */
+	u64 valid_bits = pvm->msr_ia32_feature_control_valid_bits;
+
+	if (!msr_info->host_initiated &&
+	    (pvm->msr_ia32_feature_control & FEAT_CTL_LOCKED))
+		return false;
+
+	return !(msr_info->data & ~valid_bits);
+}
+
+static void pvm_update_uret_msr(struct vcpu_pvm *pvm, unsigned int slot,
+				u64 data, u64 mask)
+{
+	preempt_disable();
+	if (pvm->loaded_cpu_state)
+		kvm_set_user_return_msr(slot, data, mask);
+	preempt_enable();
+}
+
 /*
  * Reads an msr value (of 'msr_index') into 'msr_info'.
  * Returns 0 on success, non-0 otherwise.
@@ -899,9 +925,15 @@ static int pvm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_IA32_SYSENTER_ESP:
 		msr_info->data = pvm->unused_MSR_IA32_SYSENTER_ESP;
 		break;
+	case MSR_TSC_AUX:
+		msr_info->data = pvm->msr_tsc_aux;
+		break;
 	case MSR_IA32_DEBUGCTLMSR:
 		msr_info->data = 0;
 		break;
+	case MSR_IA32_FEAT_CTL:
+		msr_info->data = pvm->msr_ia32_feature_control;
+		break;
 	case MSR_PVM_VCPU_STRUCT:
 		msr_info->data = pvm->msr_vcpu_struct;
 		break;
@@ -988,9 +1020,18 @@ static int pvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_IA32_SYSENTER_ESP:
 		pvm->unused_MSR_IA32_SYSENTER_ESP = data;
 		break;
+	case MSR_TSC_AUX:
+		pvm->msr_tsc_aux = data;
+		pvm_update_uret_msr(pvm, 1, data, -1ull);
+		break;
 	case MSR_IA32_DEBUGCTLMSR:
 		/* It is ignored now. */
 		break;
+	case MSR_IA32_FEAT_CTL:
+		if (!is_intel || !is_pvm_feature_control_msr_valid(pvm, msr_info))
+			return 1;
+		pvm->msr_ia32_feature_control = data;
+		break;
 	case MSR_MISC_FEATURES_ENABLES:
 		ret = kvm_set_msr_common(vcpu, msr_info);
 		if (!ret)
-- 
2.19.1.6.gb485710b