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

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Message-ID: <68b180fa-75ee-08b9-aa6b-2afeac860462@amd.com>
Date:   Thu, 16 Feb 2023 14:50:09 +0100
From:   "Gupta, Pankaj" <pankaj.gupta@....com>
To:     Tianyu Lan <ltykernel@...il.com>, luto@...nel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        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
Cc:     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 2/3/2023 8:27 AM, Tianyu Lan wrote:
> On 1/23/2023 3:33 PM, Gupta, Pankaj wrote:
>>
>>> + */
>>> +.macro idtentry_hv vector asmsym cfunc
>>> +SYM_CODE_START(\asmsym)
>>> +    UNWIND_HINT_IRET_REGS
>>> +    ASM_CLAC
>>
>> Did you get a chance to review the new instructions
>> added at the start similar to idtentry_vc and comments
>> added assuggested here?
>>
>> https://lore.kernel.org/lkml/16e50239-39b2-4fb4-5110-18f13ba197fe@amd.com/
> 
> Hi Pankaj:
>      Thanks for your reminder. Yes, CLD should be add after ASM_CLAC. 
> Will fix it.

Also it looks ENDBR also needs to be added before ASM_CLAC? as I also 
get this:

vmlinux.o: warning: objtool: asm_exc_hv_injection+0x0: 
UNWIND_HINT_IRET_REGS without ENDBR
vmlinux.o: warning: objtool: ibt_selftest+0x11: sibling call from 
callable instruction with modified stack frame
vmlinux.o: warning: objtool: ibt_selftest+0x1e: return with modified 
stack frame
vmlinux.o: warning: objtool: def_idts+0x1d8: data relocation to !ENDBR: 
asm_exc_hv_injection+0x0

Thanks,
Pankaj