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AJvYcCX7TsS/7HhMOC96nh3R8h4N4Kse0IVYZtR7/cCsYGjfLV+omaE5r8iEc1hEJEad1DPVvqQ=@vger.kernel.org X-Gm-Message-State: AOJu0Ywz8SU2uUsiVEZEMVmyvsyJ4DdIfk5+y9uRzbS2rlEe2Z06g1Hv st5jZy2uDZ/HzPGb3zWB6Q2WxgynQtznJ/vTup+9mta/w2vbjBAHufsFTzd2vlobJMzCfPt3OJ7 KL9gaDg== X-Google-Smtp-Source: AGHT+IFqigLk0NIDwkjpeb5ApxutUdruTchcEBopM6slK/JX5IYYl81HW/7KTMr5YJOPKSr3iVnXbFeNfn0= X-Received: from pfbho2.prod.google.com ([2002:a05:6a00:8802:b0:747:b76c:ab92]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:2d43:b0:21d:8dc:796d with SMTP id adf61e73a8af0-21ee254c5c0mr5268731637.23.1749250468097; Fri, 06 Jun 2025 15:54:28 -0700 (PDT) Date: Fri, 6 Jun 2025 15:54:26 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250605192643.533502-1-seanjc@google.com> <20250605192643.533502-3-seanjc@google.com> Message-ID: Subject: Re: [kvm-unit-tests PATCH 2/3] x86/msr: Add a testcase to verify SPEC_CTRL exists (or not) as expected From: Sean Christopherson To: Chao Gao Cc: Paolo Bonzini , kvm@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Fri, Jun 06, 2025, Chao Gao wrote: > On Thu, Jun 05, 2025 at 12:26:42PM -0700, Sean Christopherson wrote: > >diff --git a/x86/msr.c b/x86/msr.c > >index ac12d127..ca265fac 100644 > >--- a/x86/msr.c > >+++ b/x86/msr.c > >@@ -290,10 +290,37 @@ static void test_x2apic_msrs(void) > > __test_x2apic_msrs(true); > > } > > > >-static void test_cmd_msrs(void) > >+static void test_mitigation_msrs(void) > > { > >+ u64 spec_ctrl_bits = 0, val; > > int i; > > > >+ if (this_cpu_has(X86_FEATURE_SPEC_CTRL) || this_cpu_has(X86_FEATURE_AMD_IBRS)) > >+ spec_ctrl_bits |= SPEC_CTRL_IBRS; > >+ > >+ if (this_cpu_has(X86_FEATURE_SPEC_CTRL) || this_cpu_has(X86_FEATURE_AMD_STIBP)) > >+ spec_ctrl_bits |= SPEC_CTRL_STIBP; > > CPUID.(EAX=07H, ECX=0):EDX[26] enumerates IBRS and IBPB support, but it doesn't > enumerate STIBP support. EDX[27] does. Drat, that's what I get for trying to reverse engineer the kernel's mitigations. It's super obvious when I actually look at the CPUID feature definitions. Thanks!