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Mon, 27 Nov 2023 23:26:51 -0800 (PST) X-Google-Smtp-Source: AGHT+IF4M7NxKP9raF3yxSld89xnv352HPd9UfYd6M9jkbwCiMadp3oGAStD9ceWph2CLoGlKw1rNQ== X-Received: by 2002:a05:600c:1f93:b0:401:2ee0:7558 with SMTP id je19-20020a05600c1f9300b004012ee07558mr10641324wmb.32.1701156411350; Mon, 27 Nov 2023 23:26:51 -0800 (PST) Received: from starship ([77.137.131.4]) by smtp.gmail.com with ESMTPSA id l15-20020a05600c4f0f00b00405959bbf4fsm16310283wmq.19.2023.11.27.23.26.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Nov 2023 23:26:51 -0800 (PST) Message-ID: <38e52b16dfb57d0759b0e196fc952f20a62b0d3f.camel@redhat.com> Subject: Re: [RFC 11/33] KVM: x86: hyper-v: Handle GET/SET_VP_REGISTER hcall in user-space From: Maxim Levitsky To: Alexander Graf , Nicolas Saenz Julienne , kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com, anelkz@amazon.com, dwmw@amazon.co.uk, jgowans@amazon.com, corbert@lwn.net, kys@microsoft.com, haiyangz@microsoft.com, decui@microsoft.com, x86@kernel.org, linux-doc@vger.kernel.org Date: Tue, 28 Nov 2023 09:26:48 +0200 In-Reply-To: References: <20231108111806.92604-1-nsaenz@amazon.com> <20231108111806.92604-12-nsaenz@amazon.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit On Wed, 2023-11-08 at 13:14 +0100, Alexander Graf wrote: > On 08.11.23 12:17, Nicolas Saenz Julienne wrote: > > Let user-space handle HVCALL_GET_VP_REGISTERS and > > HVCALL_SET_VP_REGISTERS through the KVM_EXIT_HYPERV_HVCALL exit reason. > > Additionally, expose the cpuid bit. > > > > Signed-off-by: Nicolas Saenz Julienne > > --- > > arch/x86/kvm/hyperv.c | 9 +++++++++ > > include/asm-generic/hyperv-tlfs.h | 1 + > > 2 files changed, 10 insertions(+) > > > > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > > index caaa859932c5..a3970d52eef1 100644 > > --- a/arch/x86/kvm/hyperv.c > > +++ b/arch/x86/kvm/hyperv.c > > @@ -2456,6 +2456,9 @@ static void kvm_hv_write_xmm(struct kvm_hyperv_xmm_reg *xmm) > > > > static bool kvm_hv_is_xmm_output_hcall(u16 code) > > { > > + if (code == HVCALL_GET_VP_REGISTERS) > > + return true; > > + > > return false; > > } > > > > @@ -2520,6 +2523,8 @@ static bool is_xmm_fast_hypercall(struct kvm_hv_hcall *hc) > > case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX: > > case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX: > > case HVCALL_SEND_IPI_EX: > > + case HVCALL_GET_VP_REGISTERS: > > + case HVCALL_SET_VP_REGISTERS: > > return true; > > } > > > > @@ -2738,6 +2743,9 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) > > break; > > } > > goto hypercall_userspace_exit; > > + case HVCALL_GET_VP_REGISTERS: > > + case HVCALL_SET_VP_REGISTERS: > > + goto hypercall_userspace_exit; > > default: > > ret = HV_STATUS_INVALID_HYPERCALL_CODE; > > break; > > @@ -2903,6 +2911,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, > > ent->ebx |= HV_POST_MESSAGES; > > ent->ebx |= HV_SIGNAL_EVENTS; > > ent->ebx |= HV_ENABLE_EXTENDED_HYPERCALLS; > > + ent->ebx |= HV_ACCESS_VP_REGISTERS; > > Do we need to guard this? I think so, check should be added to 'hv_check_hypercall_access'. I do wonder though why KVM can't just pass all unknown hypercalls to userspace instead of having a whitelist. Best regards, Maxim Levitsky > > > Alex > > > > > Amazon Development Center Germany GmbH > Krausenstr. 38 > 10117 Berlin > Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss > Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B > Sitz: Berlin > Ust-ID: DE 289 237 879 > >