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From: Xiaoyao Li <xiaoyao.li@intel.com>
To: Sean Christopherson <seanjc@google.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>,
	erdemaktas@google.com, Connor Kuehl <ckuehl@redhat.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, isaku.yamahata@intel.com,
	Kai Huang <kai.huang@intel.com>
Subject: Re: [PATCH 10/11] KVM: Disallow read-only memory for x86 TDX
Date: Sun, 14 Nov 2021 11:43:06 +0800	[thread overview]
Message-ID: <33598dac-d91c-c9b8-4f70-b3a0f9f20c23@intel.com> (raw)
In-Reply-To: <YY6b4n8xPaKspoNI@google.com>

On 11/13/2021 12:52 AM, Sean Christopherson wrote:
> On Fri, Nov 12, 2021, Xiaoyao Li wrote:
>> From: Isaku Yamahata <isaku.yamahata@intel.com>
>>
>> TDX doesn't expose permission bits to the VMM in the SEPT tables, i.e.,
>> doesn't support read-only private memory.
>>
>> Introduce kvm_arch_support_readonly_mem(), which returns true except for
>> x86. x86 has its own implementation based on vm_type that returns faluse
>> for TDX VM.
>>
>> Propagate it to KVM_CAP_READONLY_MEM to allow reporting on a per-VM
>> basis.
> 
> Assuming KVM gains support for private memslots (or memslots that _may_ be mapped
> private), this is incorrect, the restriction on read-only memory only applies to
> private memory.  Userspace should still be allowed to create read-only shared memory.
> Ditto for dirty-logging in the next patch.

Yes. I had the same concern before sending it out. :)
But I forgot to mention it.

> When this patch was originally created, it was "correct" because there was no
> (proposed) concept of a private memslot or of a memslot that can be mapped private.
> 
> So these two patches at least need to wait until KVM has a defind ABI for managing
> guest private memory.
> 

I'll drop the two patches for next submission.

  reply	other threads:[~2021-11-14  3:43 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-12 15:37 [PATCH 00/11] KVM: x86: TDX preparation of introducing vm_type and blocking ioctls based on vm_type Xiaoyao Li
2021-11-12 15:37 ` [PATCH 01/11] KVM: x86: Introduce vm_type to differentiate normal VMs from confidential VMs Xiaoyao Li
2021-11-12 16:47   ` Sean Christopherson
2021-11-15 15:37     ` Xiaoyao Li
2021-11-12 15:37 ` [PATCH 02/11] KVM: x86: Disable direct IRQ injection for TDX Xiaoyao Li
2021-11-12 15:37 ` [PATCH 03/11] KVM: x86: Clean up kvm_vcpu_ioctl_x86_setup_mce() Xiaoyao Li
2021-12-02  1:19   ` Xiaoyao Li
2021-11-12 15:37 ` [PATCH 04/11] KVM: x86: Disable MCE related stuff for TDX Xiaoyao Li
2021-11-12 17:01   ` Sean Christopherson
2021-11-15 15:39     ` Xiaoyao Li
2021-11-12 15:37 ` [PATCH 05/11] KVM: x86: Disallow tsc manipulation " Xiaoyao Li
2021-11-12 15:37 ` [PATCH 06/11] KVM: x86: Disable in-kernel I/O APIC and level routes " Xiaoyao Li
2021-11-12 15:37 ` [PATCH 07/11] KVM: x86: Disable SMM " Xiaoyao Li
2021-11-12 18:04   ` Sean Christopherson
2021-11-12 18:35     ` Sean Christopherson
2021-12-01  6:29     ` Xiaoyao Li
2021-11-12 15:37 ` [PATCH 08/11] KVM: x86: Disable INIT/SIPI " Xiaoyao Li
2021-11-12 15:37 ` [PATCH 09/11] KVM: x86: Block ioctls to access guest state " Xiaoyao Li
2021-11-12 15:37 ` [PATCH 10/11] KVM: Disallow read-only memory for x86 TDX Xiaoyao Li
2021-11-12 16:52   ` Sean Christopherson
2021-11-14  3:43     ` Xiaoyao Li [this message]
2021-11-12 15:37 ` [PATCH 11/11] KVM: Disallow dirty logging " Xiaoyao Li

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