linux-kernel - [PATCH] KVM: vmx/pmu: Add VMCS fields check before exposing LBR

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Wed,  3 Feb 2021 14:50:27 +0800
From:   Like Xu <like.xu@...ux.intel.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     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>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: vmx/pmu: Add VMCS fields check before exposing LBR_FMT

Before KVM exposes guest LBR_FMT perf capabilities, it needs to check
whether VMCS has GUEST_IA32_DEBUGCTL guest status field and vmx switch
support on IA32_DEBUGCTL MSR (including VM_EXIT_SAVE_DEBUG_CONTROLS
and VM_ENTRY_LOAD_DEBUG_CONTROLS). It helps nested LBR enablement.

Signed-off-by: Like Xu <like.xu@...ux.intel.com>
---
 arch/x86/kvm/vmx/capabilities.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index d1d77985e889..ac3af06953a8 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -378,6 +378,12 @@ static inline bool vmx_pt_mode_is_host_guest(void)
 	return pt_mode == PT_MODE_HOST_GUEST;
 }
 
+static inline bool cpu_has_vmx_lbr(void)
+{
+	return (vmcs_config.vmexit_ctrl & VM_EXIT_SAVE_DEBUG_CONTROLS) &&
+		(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_DEBUG_CONTROLS);
+}
+
 static inline u64 vmx_get_perf_capabilities(void)
 {
 	u64 perf_cap = 0;
@@ -385,7 +391,8 @@ static inline u64 vmx_get_perf_capabilities(void)
 	if (boot_cpu_has(X86_FEATURE_PDCM))
 		rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_cap);
 
-	perf_cap &= PMU_CAP_LBR_FMT;
+	if (cpu_has_vmx_lbr())
+		perf_cap &= PMU_CAP_LBR_FMT;
 
 	/*
 	 * Since counters are virtualized, KVM would support full
-- 
2.29.2