linux-kernel - Re: [PATCH v13 09/35] KVM: Add KVM_EXIT_MEMORY_FAULT exit to report faults to userspace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <482bfea6f54ea1bb7d1ad75e03541d0ba0e5be6f.camel@intel.com>
Date:   Wed, 1 Nov 2023 10:52:47 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "brauner@...nel.org" <brauner@...nel.org>,
        "oliver.upton@...ux.dev" <oliver.upton@...ux.dev>,
        "chenhuacai@...nel.org" <chenhuacai@...nel.org>,
        "paul.walmsley@...ive.com" <paul.walmsley@...ive.com>,
        "palmer@...belt.com" <palmer@...belt.com>,
        "maz@...nel.org" <maz@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "willy@...radead.org" <willy@...radead.org>,
        "anup@...infault.org" <anup@...infault.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
CC:     "Li, Xiaoyao" <xiaoyao.li@...el.com>,
        "kvm-riscv@...ts.infradead.org" <kvm-riscv@...ts.infradead.org>,
        "mic@...ikod.net" <mic@...ikod.net>,
        "liam.merwick@...cle.com" <liam.merwick@...cle.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "david@...hat.com" <david@...hat.com>,
        "tabba@...gle.com" <tabba@...gle.com>,
        "amoorthy@...gle.com" <amoorthy@...gle.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "michael.roth@....com" <michael.roth@....com>,
        "kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "Annapurve, Vishal" <vannapurve@...gle.com>,
        "vbabka@...e.cz" <vbabka@...e.cz>,
        "mail@...iej.szmigiero.name" <mail@...iej.szmigiero.name>,
        "yu.c.zhang@...ux.intel.com" <yu.c.zhang@...ux.intel.com>,
        "qperret@...gle.com" <qperret@...gle.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "Xu, Yilun" <yilun.xu@...el.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "ackerleytng@...gle.com" <ackerleytng@...gle.com>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Wang, Wei W" <wei.w.wang@...el.com>
Subject: Re: [PATCH v13 09/35] KVM: Add KVM_EXIT_MEMORY_FAULT exit to report
 faults to userspace


> +7.34 KVM_CAP_MEMORY_FAULT_INFO
> +------------------------------
> +
> +:Architectures: x86
> +:Returns: Informational only, -EINVAL on direct KVM_ENABLE_CAP.
> +
> +The presence of this capability indicates that KVM_RUN will fill
> +kvm_run.memory_fault if KVM cannot resolve a guest page fault VM-Exit, e.g. if
> +there is a valid memslot but no backing VMA for the corresponding host virtual
> +address.
> +
> +The information in kvm_run.memory_fault is valid if and only if KVM_RUN returns
> +an error with errno=EFAULT or errno=EHWPOISON *and* kvm_run.exit_reason is set
> +to KVM_EXIT_MEMORY_FAULT.

IIUC returning -EFAULT or whatever -errno is sort of KVM internal
implementation.  Is it better to relax the validity of kvm_run.memory_fault when
KVM_RUN returns any -errno?

[...]


> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2327,4 +2327,15 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
>  /* Max number of entries allowed for each kvm dirty ring */
>  #define  KVM_DIRTY_RING_MAX_ENTRIES  65536
>  
> +static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
> +						 gpa_t gpa, gpa_t size)
> +{
> +	vcpu->run->exit_reason = KVM_EXIT_MEMORY_FAULT;
> +	vcpu->run->memory_fault.gpa = gpa;
> +	vcpu->run->memory_fault.size = size;
> +
> +	/* Flags are not (yet) defined or communicated to userspace. */
> +	vcpu->run->memory_fault.flags = 0;
> +}
> +

KVM_CAP_MEMORY_FAULT_INFO is x86 only, is it better to put this function to
<asm/kvm_host.h>?