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Mon, 09 Sep 2024 06:59:36 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFNaWA+QcPPrm8bvTDzmFg3kG3BrB9jWkRT4CRrCmQChDuuMC4Rev7/APmGPLXzL0N7t7K/Ww== X-Received: by 2002:adf:f489:0:b0:374:baf1:41bb with SMTP id ffacd0b85a97d-37892685979mr3763824f8f.3.1725890375638; Mon, 09 Sep 2024 06:59:35 -0700 (PDT) Received: from [192.168.10.81] ([151.95.101.29]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-42caeb449aesm77452765e9.25.2024.09.09.06.59.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Sep 2024 06:59:35 -0700 (PDT) Message-ID: Date: Mon, 9 Sep 2024 15:59:34 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 05/21] KVM: VMX: Teach EPT violation helper about private mem To: Rick Edgecombe , seanjc@google.com, kvm@vger.kernel.org Cc: kai.huang@intel.com, dmatlack@google.com, isaku.yamahata@gmail.com, yan.y.zhao@intel.com, nik.borisov@suse.com, linux-kernel@vger.kernel.org References: <20240904030751.117579-1-rick.p.edgecombe@intel.com> <20240904030751.117579-6-rick.p.edgecombe@intel.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/4/24 05:07, Rick Edgecombe wrote: > Teach EPT violation helper to check shared mask of a GPA to find out > whether the GPA is for private memory. > > When EPT violation is triggered after TD accessing a private GPA, KVM will > exit to user space if the corresponding GFN's attribute is not private. > User space will then update GFN's attribute during its memory conversion > process. After that, TD will re-access the private GPA and trigger EPT > violation again. Only with GFN's attribute matches to private, KVM will > fault in private page, map it in mirrored TDP root, and propagate changes > to private EPT to resolve the EPT violation. > > Relying on GFN's attribute tracking xarray to determine if a GFN is > private, as for KVM_X86_SW_PROTECTED_VM, may lead to endless EPT > violations. > > Co-developed-by: Yan Zhao > Signed-off-by: Yan Zhao > Signed-off-by: Rick Edgecombe > --- > TDX MMU part 2 v1: > - Split from "KVM: TDX: handle ept violation/misconfig exit" > --- > arch/x86/kvm/vmx/common.h | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/arch/x86/kvm/vmx/common.h b/arch/x86/kvm/vmx/common.h > index 78ae39b6cdcd..10aa12d45097 100644 > --- a/arch/x86/kvm/vmx/common.h > +++ b/arch/x86/kvm/vmx/common.h > @@ -6,6 +6,12 @@ > > #include "mmu.h" > > +static inline bool kvm_is_private_gpa(struct kvm *kvm, gpa_t gpa) > +{ > + /* For TDX the direct mask is the shared mask. */ > + return !kvm_is_addr_direct(kvm, gpa); > +} > + > static inline int __vmx_handle_ept_violation(struct kvm_vcpu *vcpu, gpa_t gpa, > unsigned long exit_qualification) > { > @@ -28,6 +34,13 @@ static inline int __vmx_handle_ept_violation(struct kvm_vcpu *vcpu, gpa_t gpa, > error_code |= (exit_qualification & EPT_VIOLATION_GVA_TRANSLATED) ? > PFERR_GUEST_FINAL_MASK : PFERR_GUEST_PAGE_MASK; > > + /* > + * Don't rely on GFN's attribute tracking xarray to prevent EPT violation > + * loops. > + */ > + if (kvm_is_private_gpa(vcpu->kvm, gpa)) > + error_code |= PFERR_PRIVATE_ACCESS; > + > return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0); > } > Reviewed-by: Paolo Bonzini