linux-kernel - Re: [PATCH v3 24/25] KVM: TDX: Guard VM state transitions with "all" the locks

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: <55461c549803e08db97528127c29e092c597adc5.camel@intel.com>
Date: Tue, 28 Oct 2025 00:28:21 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "chenhuacai@...nel.org" <chenhuacai@...nel.org>, "frankja@...ux.ibm.com"
	<frankja@...ux.ibm.com>, "maz@...nel.org" <maz@...nel.org>,
	"borntraeger@...ux.ibm.com" <borntraeger@...ux.ibm.com>, "pjw@...nel.org"
	<pjw@...nel.org>, "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
	"kas@...nel.org" <kas@...nel.org>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"maobibo@...ngson.cn" <maobibo@...ngson.cn>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "maddy@...ux.ibm.com" <maddy@...ux.ibm.com>,
	"palmer@...belt.com" <palmer@...belt.com>, "imbrenda@...ux.ibm.com"
	<imbrenda@...ux.ibm.com>, "zhaotianrui@...ngson.cn"
	<zhaotianrui@...ngson.cn>, "anup@...infault.org" <anup@...infault.org>,
	"oliver.upton@...ux.dev" <oliver.upton@...ux.dev>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "Zhao, Yan Y" <yan.y.zhao@...el.com>,
	"michael.roth@....com" <michael.roth@....com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Weiny, Ira" <ira.weiny@...el.com>,
	"loongarch@...ts.linux.dev" <loongarch@...ts.linux.dev>,
	"binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>,
	"ackerleytng@...gle.com" <ackerleytng@...gle.com>, "kvmarm@...ts.linux.dev"
	<kvmarm@...ts.linux.dev>, "kvm-riscv@...ts.infradead.org"
	<kvm-riscv@...ts.infradead.org>, "Annapurve, Vishal" <vannapurve@...gle.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>, "Edgecombe,
 Rick P" <rick.p.edgecombe@...el.com>, "linux-mips@...r.kernel.org"
	<linux-mips@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-riscv@...ts.infradead.org"
	<linux-riscv@...ts.infradead.org>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v3 24/25] KVM: TDX: Guard VM state transitions with "all"
 the locks

On Thu, 2025-10-16 at 17:32 -0700, Sean Christopherson wrote:
> @@ -2781,8 +2827,6 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
>  	if (r)
>  		return r;
>  
> -	guard(mutex)(&kvm->lock);
> -
>  	switch (tdx_cmd.id) {
>  	case KVM_TDX_CAPABILITIES:
>  		r = tdx_get_capabilities(&tdx_cmd);

IIRC, this patch removes grabbing the kvm->lock in tdx_vm_ioctl() but only
adds the "big hammer" to tdx_td_init() and tdx_td_finalize(), so the
tdx_get_capabilities() lost holding the kvm->lock.

As replied earlier, I think we can just hold the "big hammer" in
tdx_vm_ioctl()?

One thing is when tdx_vm_ioctl() is called, the TD may not have any vCPU
(e.g., for tdx_td_init()).  This means the "big hammer" will hold kvm-
>slots_lock w/o holding any lock of vCPU.  But IIUC this should be OK.