linux-kernel - Re: [PATCH v2 21/24] KVM: TDX: Add an ioctl to create initial guest memory

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Message-ID: <Z0fTaqabmj27OJqe@yzhao56-desk.sh.intel.com>
Date: Thu, 28 Nov 2024 10:20:26 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Nikolay Borisov <nik.borisov@...e.com>
CC: <pbonzini@...hat.com>, <seanjc@...gle.com>, <kvm@...r.kernel.org>,
	<dave.hansen@...ux.intel.com>, <rick.p.edgecombe@...el.com>,
	<kai.huang@...el.com>, <adrian.hunter@...el.com>,
	<reinette.chatre@...el.com>, <xiaoyao.li@...el.com>,
	<tony.lindgren@...el.com>, <binbin.wu@...ux.intel.com>,
	<dmatlack@...gle.com>, <isaku.yamahata@...el.com>,
	<isaku.yamahata@...il.com>, <linux-kernel@...r.kernel.org>, <x86@...nel.org>
Subject: Re: [PATCH v2 21/24] KVM: TDX: Add an ioctl to create initial guest
 memory

On Wed, Nov 27, 2024 at 08:08:26PM +0200, Nikolay Borisov wrote:
> 
> On 12.11.24 г. 9:38 ч., Yan Zhao wrote:
> > +static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd)
> > +{
> > +	struct vcpu_tdx *tdx = to_tdx(vcpu);
> > +	struct kvm *kvm = vcpu->kvm;
> > +	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> > +	struct kvm_tdx_init_mem_region region;
> > +	struct tdx_gmem_post_populate_arg arg;
> > +	long gmem_ret;
> > +	int ret;
> > +
> > +	if (tdx->state != VCPU_TD_STATE_INITIALIZED)
> > +		return -EINVAL;
> > +
> > +	guard(mutex)(&kvm->slots_lock);
> 
> It seems the scope of this lock can be reduced. It's really needed for the
> kvm_gmem_populate call only, no ?
Strictly speaking, yes.
But this KVM_TDX_INIT_MEM_REGION ioctl is only expected to be executed after
QEMU machine creation done and before any vCPU starts running. So no slot
changes are expected during the ioctl.