linux-kernel - [PATCH v2 2/2] KVM: x86/emulator: Emulate RDPID only if it is enabled in guest

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Message-Id: <45a2dbcbf694c48f1fb6a834a0f97a36a226a172.1646655860.git.houwenlong.hwl@antgroup.com>
Date:   Mon, 07 Mar 2022 20:26:34 +0800
From:   "Hou Wenlong" <houwenlong.hwl@...group.com>
To:     kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] KVM: x86/emulator: Emulate RDPID only if it is enabled in guest

When RDTSCP is supported but RDPID is not supported in host,
RDPID emulation is available. However, __kvm_get_msr() would
only fail when RDTSCP/RDPID both are disabled in guest, so
the emulator wouldn't inject a #UD when RDPID is disabled but
RDTSCP is enabled in guest.

Fixes: fb6d4d340e05 ("KVM: x86: emulate RDPID")
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/kvm/emulate.c     | 4 +++-
 arch/x86/kvm/kvm_emulate.h | 1 +
 arch/x86/kvm/x86.c         | 6 ++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 3497a35bd085..be83c9c8482d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3521,8 +3521,10 @@ static int em_rdpid(struct x86_emulate_ctxt *ctxt)
 {
 	u64 tsc_aux = 0;
 
-	if (ctxt->ops->get_msr(ctxt, MSR_TSC_AUX, &tsc_aux))
+	if (!ctxt->ops->guest_has_rdpid(ctxt))
 		return emulate_ud(ctxt);
+
+	ctxt->ops->get_msr(ctxt, MSR_TSC_AUX, &tsc_aux);
 	ctxt->dst.val = tsc_aux;
 	return X86EMUL_CONTINUE;
 }
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 29ac5a9679e5..1cbd46cf71f9 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -228,6 +228,7 @@ struct x86_emulate_ops {
 	bool (*guest_has_long_mode)(struct x86_emulate_ctxt *ctxt);
 	bool (*guest_has_movbe)(struct x86_emulate_ctxt *ctxt);
 	bool (*guest_has_fxsr)(struct x86_emulate_ctxt *ctxt);
+	bool (*guest_has_rdpid)(struct x86_emulate_ctxt *ctxt);
 
 	void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 09c5677f4186..44f97038d3e5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7723,6 +7723,11 @@ static bool emulator_guest_has_fxsr(struct x86_emulate_ctxt *ctxt)
 	return guest_cpuid_has(emul_to_vcpu(ctxt), X86_FEATURE_FXSR);
 }
 
+static bool emulator_guest_has_rdpid(struct x86_emulate_ctxt *ctxt)
+{
+	return guest_cpuid_has(emul_to_vcpu(ctxt), X86_FEATURE_RDPID);
+}
+
 static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg)
 {
 	return kvm_register_read_raw(emul_to_vcpu(ctxt), reg);
@@ -7807,6 +7812,7 @@ static const struct x86_emulate_ops emulate_ops = {
 	.guest_has_long_mode = emulator_guest_has_long_mode,
 	.guest_has_movbe     = emulator_guest_has_movbe,
 	.guest_has_fxsr      = emulator_guest_has_fxsr,
+	.guest_has_rdpid     = emulator_guest_has_rdpid,
 	.set_nmi_mask        = emulator_set_nmi_mask,
 	.get_hflags          = emulator_get_hflags,
 	.exiting_smm         = emulator_exiting_smm,
-- 
2.31.1