From: Sean Christopherson <seanjc@google.com>
To: Zeng Guang <guang.zeng@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
Tony Luck <tony.luck@intel.com>,
Kan Liang <kan.liang@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Kim Phillips <kim.phillips@amd.com>,
Jarkko Sakkinen <jarkko@kernel.org>,
Jethro Beekman <jethro@fortanix.com>,
Kai Huang <kai.huang@intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Robert Hu <robert.hu@intel.com>, Gao Chao <chao.gao@intel.com>
Subject: Re: [PATCH v8 9/9] KVM: VMX: enable IPI virtualization
Date: Fri, 15 Apr 2022 15:25:06 +0000 [thread overview]
Message-ID: <YlmOUtXgIdQcUTO1@google.com> (raw)
In-Reply-To: <20220411090447.5928-10-guang.zeng@intel.com>
On Mon, Apr 11, 2022, Zeng Guang wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d1a39285deab..23fbf52f7bea 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -11180,11 +11180,15 @@ static int sync_regs(struct kvm_vcpu *vcpu)
>
> int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id)
> {
> + int ret = 0;
> +
> if (kvm_check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0)
> pr_warn_once("kvm: SMP vm created on host with unstable TSC; "
> "guest TSC will not be reliable\n");
>
> - return 0;
> + if (kvm_x86_ops.alloc_ipiv_pid_table)
> + ret = static_call(kvm_x86_alloc_ipiv_pid_table)(kvm);
Add a generic kvm_x86_ops.vcpu_precreate, no reason to make this so specific.
And use KVM_X86_OP_RET0 instead of KVM_X86_OP_OPTIONAL, then this can simply be
return static_call(kvm_x86_vcpu_precreate);
That said, there's a flaw in my genius plan.
1. KVM_CREATE_VM
2. KVM_CAP_MAX_VCPU_ID, set max_vcpu_ids=1
3. KVM_CREATE_VCPU, create IPIv table but ultimately fails
4. KVM decrements created_vcpus back to '0'
5. KVM_CAP_MAX_VCPU_ID, set max_vcpu_ids=4096
6. KVM_CREATE_VCPU w/ ID out of range
In other words, malicious userspace could trigger buffer overflow.
That could be solved by adding an arch hook to undo precreate, but that's gross
and a good indication that we're trying to solve this the wrong way.
I think it's high time we add KVM_FINALIZE_VM, though that's probably a bad name
since e.g. TDX wants to use that name for VM really, really, being finalized[*],
i.e. after all vCPUs have been created.
KVM_POST_CREATE_VM? That's not very good either.
Paolo or anyone else, thoughts?
[*] https://lore.kernel.org/all/83768bf0f786d24f49d9b698a45ba65441ef5ef0.1646422845.git.isaku.yamahata@intel.com
next prev parent reply other threads:[~2022-04-15 15:25 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-11 9:04 [PATCH v8 0/9] IPI virtualization support for VM Zeng Guang
2022-04-11 9:04 ` [PATCH v8 1/9] x86/cpu: Add new VMX feature, Tertiary VM-Execution control Zeng Guang
2022-04-11 9:04 ` [PATCH v8 2/9] KVM: VMX: Extend BUILD_CONTROLS_SHADOW macro to support 64-bit variation Zeng Guang
2022-04-11 9:04 ` [PATCH v8 3/9] KVM: VMX: Detect Tertiary VM-Execution control when setup VMCS config Zeng Guang
2022-04-11 9:04 ` [PATCH v8 4/9] KVM: VMX: Report tertiary_exec_control field in dump_vmcs() Zeng Guang
2022-04-11 9:04 ` [PATCH v8 5/9] KVM: x86: Add support for vICR APIC-write VM-Exits in x2APIC mode Zeng Guang
2022-04-11 9:04 ` [PATCH v8 6/9] KVM: x86: lapic: don't allow to change APIC ID unconditionally Zeng Guang
2022-04-15 14:39 ` Sean Christopherson
2022-04-19 14:07 ` Maxim Levitsky
2022-04-26 8:14 ` Maxim Levitsky
2022-04-26 14:00 ` Chao Gao
2022-04-11 9:04 ` [PATCH v8 7/9] KVM: Move kvm_arch_vcpu_precreate() under kvm->lock Zeng Guang
2022-04-15 15:00 ` Sean Christopherson
2022-04-15 15:11 ` Sean Christopherson
2022-04-11 9:04 ` [PATCH v8 8/9] KVM: x86: Allow userspace set maximum VCPU id for VM Zeng Guang
2022-04-15 15:01 ` Sean Christopherson
2022-04-11 9:04 ` [PATCH v8 9/9] KVM: VMX: enable IPI virtualization Zeng Guang
2022-04-15 15:25 ` Sean Christopherson [this message]
2022-04-18 9:25 ` Chao Gao
2022-04-18 15:14 ` Sean Christopherson
2022-04-19 0:00 ` Chao Gao
2022-04-18 12:49 ` Zeng Guang
2022-04-15 15:45 ` Sean Christopherson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YlmOUtXgIdQcUTO1@google.com \
--to=seanjc@google.com \
--cc=bp@alien8.de \
--cc=chao.gao@intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=guang.zeng@intel.com \
--cc=hpa@zytor.com \
--cc=jarkko@kernel.org \
--cc=jethro@fortanix.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kai.huang@intel.com \
--cc=kan.liang@linux.intel.com \
--cc=kim.phillips@amd.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=robert.hu@intel.com \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).