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

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Message-ID: <ea387ecf-ac5a-4a22-e99c-bc283b39c1e1@gmail.com>
Date:   Fri, 10 Mar 2023 23:48:48 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     "Gupta, Pankaj" <pankaj.gupta@....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 3/9/2023 7:48 PM, Gupta, Pankaj wrote:
> On 1/22/2023 3:46 AM, Tianyu Lan wrote:
>> From: Tianyu Lan <tiala@...rosoft.com>
>> +    UNWIND_HINT_IRET_REGS
>> +    ASM_CLAC
>> +    pushq    $-1            /* ORIG_RAX: no syscall to restart */
>> +
>> +    testb    $3, CS-ORIG_RAX(%rsp)
>> +    jnz    .Lfrom_usermode_switch_stack_\@
>> +
>> +    call    paranoid_entry
>> +
>> +    UNWIND_HINT_REGS
>> +
>> +    /*
>> +     * Switch off the IST stack to make it free for nested exceptions.
>> +     */
>> +    movq    %rsp, %rdi        /* pt_regs pointer */
>> +    call    hv_switch_off_ist
>> +    movq    %rax, %rsp        /* Switch to new stack */
>> +
> 
> We need "ENCODE_FRAME_POINTER" similar to "vc_switch_off_ist" here as we 
> are switching stack?
> 

Agree. Will add it into the next version. Thanks.