linux-kernel - Re: [PATCH 21/25] KVM: x86: Introduce KVM_TDX_GET

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: <a59e021f-fe90-41d1-aa8d-6ce0a0abcfcc@redhat.com>
Date: Tue, 10 Sep 2024 19:29:13 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Tony Lindgren <tony.lindgren@...ux.intel.com>,
 Xu Yilun <yilun.xu@...ux.intel.com>
Cc: Rick Edgecombe <rick.p.edgecombe@...el.com>, seanjc@...gle.com,
 kvm@...r.kernel.org, kai.huang@...el.com, isaku.yamahata@...il.com,
 xiaoyao.li@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 21/25] KVM: x86: Introduce KVM_TDX_GET_CPUID

On 9/3/24 09:19, Tony Lindgren wrote:
>>> +			gpa_t gpa_bits = gfn_to_gpa(kvm_gfn_direct_bits(vcpu->kvm));
>>> +			unsigned int g_maxpa = __ffs(gpa_bits) + 1;
>>> +
>>> +			output_e->eax &= ~0x00ff0000;
>>> +			output_e->eax |= g_maxpa << 16;
>> Is it possible this workaround escapes the KVM supported bits check?
>
> Yes it might need a mask for (g_maxpa << 16) & 0x00ff0000 to avoid setting
> the wrong bits, will check.

The mask is okay, __ffs(gpa_bits) + 1 will be between 1 and 64.

The question is whether the TDX module will accept nonzero bits 16..23 
of CPUID[0x80000008].EAX.

Paolo