linux-kernel - Re: [RFC PATCH V3 12/16] x86/sev: Add a #HV exception handler

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Date:   Tue, 4 Apr 2023 02:09:46 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     luto@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        seanjc@...gle.com, pbonzini@...hat.com, jgross@...e.com,
        tiala@...rosoft.com, kirill@...temov.name,
        jiangshan.ljs@...group.com, peterz@...radead.org,
        ashish.kalra@....com, srutherford@...gle.com,
        akpm@...ux-foundation.org, anshuman.khandual@....com,
        pawan.kumar.gupta@...ux.intel.com, adrian.hunter@...el.com,
        daniel.sneddon@...ux.intel.com, alexander.shishkin@...ux.intel.com,
        sandipan.das@....com, ray.huang@....com, brijesh.singh@....com,
        michael.roth@....com, thomas.lendacky@....com,
        venu.busireddy@...cle.com, sterritt@...gle.com,
        tony.luck@...el.com, samitolvanen@...gle.com, fenghua.yu@...el.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH V3 12/16] x86/sev: Add a #HV exception handler

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.