Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.32 as permitted sender) client-ip=23.128.96.32;
Message-ID: <496b78bb-ad12-4eed-a62c-8c2fd725ec61@redhat.com>
Date:   Thu, 2 Nov 2023 12:03:39 +0100
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v13 09/35] KVM: Add KVM_EXIT_MEMORY_FAULT exit to report
 faults to userspace
Content-Language: en-US
To:     "Huang, Kai" <kai.huang@intel.com>,
        "Christopherson,, Sean" <seanjc@google.com>
Cc:     "Li, Xiaoyao" <xiaoyao.li@intel.com>,
        "kvm-riscv@lists.infradead.org" <kvm-riscv@lists.infradead.org>,
        "mic@digikod.net" <mic@digikod.net>,
        "liam.merwick@oracle.com" <liam.merwick@oracle.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@intel.com>,
        "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
        "kirill.shutemov@linux.intel.com" <kirill.shutemov@linux.intel.com>,
        "david@redhat.com" <david@redhat.com>,
        "linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
        "amoorthy@google.com" <amoorthy@google.com>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "tabba@google.com" <tabba@google.com>,
        "kvmarm@lists.linux.dev" <kvmarm@lists.linux.dev>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "oliver.upton@linux.dev" <oliver.upton@linux.dev>,
        "michael.roth@amd.com" <michael.roth@amd.com>,
        "chao.p.peng@linux.intel.com" <chao.p.peng@linux.intel.com>,
        "palmer@dabbelt.com" <palmer@dabbelt.com>,
        "chenhuacai@kernel.org" <chenhuacai@kernel.org>,
        "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
        "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
        "Annapurve, Vishal" <vannapurve@google.com>,
        "vbabka@suse.cz" <vbabka@suse.cz>,
        "mail@maciej.szmigiero.name" <mail@maciej.szmigiero.name>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "maz@kernel.org" <maz@kernel.org>,
        "willy@infradead.org" <willy@infradead.org>,
        "dmatlack@google.com" <dmatlack@google.com>,
        "anup@brainfault.org" <anup@brainfault.org>,
        "yu.c.zhang@linux.intel.com" <yu.c.zhang@linux.intel.com>,
        "Xu, Yilun" <yilun.xu@intel.com>,
        "qperret@google.com" <qperret@google.com>,
        "brauner@kernel.org" <brauner@kernel.org>,
        "isaku.yamahata@gmail.com" <isaku.yamahata@gmail.com>,
        "ackerleytng@google.com" <ackerleytng@google.com>,
        "jarkko@kernel.org" <jarkko@kernel.org>,
        "paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "Wang, Wei W" <wei.w.wang@intel.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>
References: <20231027182217.3615211-1-seanjc@google.com>
 <20231027182217.3615211-10-seanjc@google.com>
 <482bfea6f54ea1bb7d1ad75e03541d0ba0e5be6f.camel@intel.com>
 <ZUKMsOdg3N9wmEzy@google.com>
 <64e3764e36ba7a00d94cc7db1dea1ef06b620aaf.camel@intel.com>
 <32cb71700aedcbd1f65276cf44a601760ffc364b.camel@intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Autocrypt: addr=pbonzini@redhat.com; keydata=
 xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2
 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04
 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX
 DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S
 P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU
 Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo
 UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC
 tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd
 wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j
 UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH
 CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E
 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj
 jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0
 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K
 CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG
 SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9
 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE
 AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB
 nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr
 bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl
 KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF
 m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk
 tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF
 dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP
 JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp
 sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD
 OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM
 GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN
 Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d
 usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL
 xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0
 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP
 dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh
 b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w=
In-Reply-To: <32cb71700aedcbd1f65276cf44a601760ffc364b.camel@intel.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 11/2/23 10:35, Huang, Kai wrote:
> IIUC KVM can already handle the case of poisoned
> page by sending signal to user app: 
> 
> 	static int kvm_handle_error_pfn(struct kvm_vcpu *vcpu, 
> 			struct kvm_page_fault *fault)                                               
> 	{       
> 		...
> 
>        		if (fault->pfn == KVM_PFN_ERR_HWPOISON) {
>               		kvm_send_hwpoison_signal(fault->slot, fault->gfn);
>                 	return RET_PF_RETRY;                                          
>         	}
> 	}

EHWPOISON is not implemented by this series, so it should be left out of 
the documentation.


> Currently as mentioned above when
> vepc fault handler cannot allocate EPC page KVM returns -EFAULT to Qemu, and
> Qemu prints ...
> 
> 	...: Bad address
> 	<dump guest cpu registers>
> 
> ... which is nonsense.
> 
> If we can use memory_fault.flags (or is 'fault_reason' a better name?) to carry
> a specific value for EPC to let Qemu know and Qemu can then do more reasonable
> things.

Yes, that's a good idea that can be implemented on top.

Paolo