Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <7efbc4fa-1797-0da8-2846-e0753e578ffe@gmail.com>
Date:   Tue, 4 Apr 2023 02:09:46 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.9.1
Subject: Re: [RFC PATCH V3 12/16] x86/sev: Add a #HV exception handler
To:     Borislav Petkov <bp@alien8.de>
Cc:     luto@kernel.org, tglx@linutronix.de, mingo@redhat.com,
        dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
        seanjc@google.com, pbonzini@redhat.com, jgross@suse.com,
        tiala@microsoft.com, kirill@shutemov.name,
        jiangshan.ljs@antgroup.com, peterz@infradead.org,
        ashish.kalra@amd.com, srutherford@google.com,
        akpm@linux-foundation.org, anshuman.khandual@arm.com,
        pawan.kumar.gupta@linux.intel.com, adrian.hunter@intel.com,
        daniel.sneddon@linux.intel.com, alexander.shishkin@linux.intel.com,
        sandipan.das@amd.com, ray.huang@amd.com, brijesh.singh@amd.com,
        michael.roth@amd.com, thomas.lendacky@amd.com,
        venu.busireddy@oracle.com, sterritt@google.com,
        tony.luck@intel.com, samitolvanen@google.com, fenghua.yu@intel.com,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-hyperv@vger.kernel.org, linux-arch@vger.kernel.org
References: <20230122024607.788454-1-ltykernel@gmail.com>
 <20230122024607.788454-13-ltykernel@gmail.com>
 <20230331155714.GCZCcC2pHVZgIHr8k8@fat_crate.local>
From:   Tianyu Lan <ltykernel@gmail.com>
In-Reply-To: <20230331155714.GCZCcC2pHVZgIHr8k8@fat_crate.local>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 3/31/2023 11:57 PM, Borislav Petkov wrote:
>> + *
>> + * If entered from kernel-mode the return stack is validated first, and if it is
>> + * not safe to use (e.g. because it points to the entry stack) the #HV handler
>> + * will switch to a fall-back stack (HV2) and call a special handler function.
>> + *
>> + * The macro is only used for one vector, but it is planned to be extended in
>> + * the future for the #HV exception.
>> + */
>> +.macro idtentry_hv vector asmsym cfunc
>> +SYM_CODE_START(\asmsym)
> ...
> 
> why is this so much duplicated code instead of sharing it with
> idtentry_vc and all the facilities it does?
> 

Hi Boris:
	#VC and #HV use different stack. I try reusing vc code path for #HV 
doesn't work. I will continue to work on this direction and report back 
later. In the RFC v4, I still keep the old version and other patches may 
be reviewed in the parellel.

Thanks.