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Message-ID: <8ea65567-ec8a-3361-e78c-c51a1d8aad47@redhat.com>
Date: Tue, 20 Jun 2023 14:39:39 +0200
From: David Hildenbrand <david@...hat.com>
To: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
"Huang, Kai" <kai.huang@...el.com>
Cc: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Hansen, Dave" <dave.hansen@...el.com>,
"Luck, Tony" <tony.luck@...el.com>,
"bagasdotme@...il.com" <bagasdotme@...il.com>,
"ak@...ux.intel.com" <ak@...ux.intel.com>,
"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
"Christopherson,, Sean" <seanjc@...gle.com>,
"Chatre, Reinette" <reinette.chatre@...el.com>,
"pbonzini@...hat.com" <pbonzini@...hat.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"Yamahata, Isaku" <isaku.yamahata@...el.com>,
"peterz@...radead.org" <peterz@...radead.org>,
"Shahar, Sagi" <sagis@...gle.com>,
"imammedo@...hat.com" <imammedo@...hat.com>,
"Gao, Chao" <chao.gao@...el.com>,
"Brown, Len" <len.brown@...el.com>,
"sathyanarayanan.kuppuswamy@...ux.intel.com"
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
"Huang, Ying" <ying.huang@...el.com>,
"Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v11 05/20] x86/virt/tdx: Add SEAMCALL infrastructure
On 20.06.23 14:20, kirill.shutemov@...ux.intel.com wrote:
> On Tue, Jun 20, 2023 at 10:37:16AM +0000, Huang, Kai wrote:
>>>> + /*
>>>> + * SEAMCALL caused #GP or #UD. By reaching here %eax contains
>>>> + * the trap number. Convert the trap number to the TDX error
>>>> + * code by setting TDX_SW_ERROR to the high 32-bits of %rax.
>>>> + *
>>>> + * Note cannot OR TDX_SW_ERROR directly to %rax as OR instruction
>>>> + * only accepts 32-bit immediate at most.
>>>
>>> Not sure if that comment is really helpful here. It's a common pattern
>>> for large immediates, no?
>>
>> I am not sure. I guess I am not expert of x86 assembly but only casual writer.
>>
>> Hi Dave, Kirill,
>>
>> Are you OK to remove it?
>
> I would rather keep it. I wanted to ask why separate MOV is needed here,
> before I read the comment. Also size of $TDX_SW_ERROR is not visible here,
> so it contributes to possible confusion without the comment.
>
Fine with me, but I'd assume that the assembler will simply complain in
case we'd try to use a large immediate.
--
Cheers,
David / dhildenb
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