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AJvYcCWlUmHElnro0gJeWhlvh5dg2U8JNIlo7zdKRHk1ssQZsNZqNKzJsnpS5u8kn3BxYTElPP1GRNswUZptdBZifW8=@vger.kernel.org X-Gm-Message-State: AOJu0YyLixURKylWgSK8zpM7KpBQG6PEGeT9NDFCw+oyctkIkdYU1WK5 7PbdQCBYFYhVleny+E5YUaBtVyEkgSpyljPx4ma6/J/bcX3bgA+5EHad5y7G2t4bBaMCTvujU7H d/Q== X-Google-Smtp-Source: AGHT+IFvMyzHs0jMD7T18ZwTYJ9lm8AXPz2gW99+UB2nn3KAXaBAX+lpyE8o2K/04Z7bT0N2PiSTsZCjzB8= X-Received: from pfbem8.prod.google.com ([2002:a05:6a00:3748:b0:739:9e9:feea]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:3e28:b0:736:4bd3:ffab with SMTP id d2e1a72fcca58-73dc1591d84mr25297228b3a.17.1745422166356; Wed, 23 Apr 2025 08:29:26 -0700 (PDT) Date: Wed, 23 Apr 2025 08:29:24 -0700 In-Reply-To: <52276154-79b0-4029-8087-77ca499a12ce@amd.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250324130248.126036-1-manali.shukla@amd.com> <20250324130248.126036-4-manali.shukla@amd.com> <52276154-79b0-4029-8087-77ca499a12ce@amd.com> Message-ID: Subject: Re: [PATCH v4 3/5] KVM: SVM: Enable Bus lock threshold exit From: Sean Christopherson To: Manali Shukla Cc: Xiaoyao Li , kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, pbonzini@redhat.com, nikunj@amd.com, thomas.lendacky@amd.com, bp@alien8.de Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Wed, Apr 23, 2025, Manali Shukla wrote: > On 4/16/2025 11:30 AM, Xiaoyao Li wrote: > >> =C2=A0 +=C2=A0=C2=A0=C2=A0 if (cpu_feature_enabled(X86_FEATURE_BUS_LOC= K_THRESHOLD)) { > >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pr_info("Bus Lock Threshol= d supported\n"); > >=20 > > It will be printed every time kvm-amd.ko module gets loaded. > >=20 > > I think it's for your development and debug purpose. Comparing to the > > existing features in svm_set_cpu_caps(), nothing makes it special for > > BUS_LOCK_THRESHOLD to require a kernel message. So I think we can just > > remove it. >=20 > I didn't add this for development and debug purpose. I added this pr_info= () > to make it easy to find whether BUS Lock threshold is supported or not fr= om > dmesg. I can remove it if you think it is not required. Please remove it. The user typically doesn't care. > >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kvm_caps.has_bus_lock_exit= =3D true; > >=20 > > Besides, this patch doesn't ensure the bisectability. It allows userspa= ce > > to enable KVM_BUS_LOCK_DETECTION_EXIT and set intercept of > > INTERCEPT_BUSLOCK but without providing the handler. > >=20 > > So either move next patch before it or just merge them. > >=20 >=20 > Oh.., my bad, I will move the next patch before this one in v5. No, do exactly as I suggested in v3. : I vote to split this into two patches: one to add the architectural coll= ateral, : with the above as the changelog, and a second to actually implement supp= ort in : KVM. Having the above background is useful, but it makes it quite hard = to find : information on the KVM design and implementation. I want this (and any other arch collateral I'm missing) in a separate patch= so that the background on what the hardware feature does is captured. But I s= ee no reason to split KVM's implementation into multiple patches. diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h index 2b59b9951c90..d1819c564b1c 100644 --- a/arch/x86/include/asm/svm.h +++ b/arch/x86/include/asm/svm.h @@ -116,6 +116,7 @@ enum { INTERCEPT_INVPCID, INTERCEPT_MCOMMIT, INTERCEPT_TLBSYNC, + INTERCEPT_BUSLOCK, }; @@ -158,7 +159,9 @@ struct __attribute__ ((__packed__)) vmcb_control_area { u64 avic_physical_id; /* Offset 0xf8 */ u8 reserved_7[8]; u64 vmsa_pa; /* Used for an SEV-ES guest */ - u8 reserved_8[720]; + u8 reserved_8[16]; + u16 bus_lock_counter; /* Offset 0x120 */ + u8 reserved_9[702]; /* * Offset 0x3e0, 32 bytes reserved * for use by hypervisor/software. diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/sv= m.h index 1814b413fd57..abf6aed88cee 100644 --- a/arch/x86/include/uapi/asm/svm.h +++ b/arch/x86/include/uapi/asm/svm.h @@ -95,6 +95,7 @@ #define SVM_EXIT_CR14_WRITE_TRAP 0x09e #define SVM_EXIT_CR15_WRITE_TRAP 0x09f #define SVM_EXIT_INVPCID 0x0a2 +#define SVM_EXIT_BUS_LOCK 0x0a5 #define SVM_EXIT_NPF 0x400 #define SVM_EXIT_AVIC_INCOMPLETE_IPI 0x401 #define SVM_EXIT_AVIC_UNACCELERATED_ACCESS 0x402 @@ -224,6 +225,7 @@ { SVM_EXIT_CR4_WRITE_TRAP, "write_cr4_trap" }, \ { SVM_EXIT_CR8_WRITE_TRAP, "write_cr8_trap" }, \ { SVM_EXIT_INVPCID, "invpcid" }, \ + { SVM_EXIT_BUS_LOCK, "buslock" }, \ { SVM_EXIT_NPF, "npf" }, \ { SVM_EXIT_AVIC_INCOMPLETE_IPI, "avic_incomplete_ipi" }, \ { SVM_EXIT_AVIC_UNACCELERATED_ACCESS, "avic_unaccelerated_access"= }, \