Message-ID: <ea387ecf-ac5a-4a22-e99c-bc283b39c1e1@gmail.com>
Date:   Fri, 10 Mar 2023 23:48:48 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.8.0
Subject: Re: [RFC PATCH V3 12/16] x86/sev: Add a #HV exception handler
To:     "Gupta, Pankaj" <pankaj.gupta@amd.com>, luto@kernel.org,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        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
Cc:     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>
 <a25a21f9-0059-3e39-4284-7c4164d170ed@amd.com>
From:   Tianyu Lan <ltykernel@gmail.com>
In-Reply-To: <a25a21f9-0059-3e39-4284-7c4164d170ed@amd.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk


On 3/9/2023 7:48 PM, Gupta, Pankaj wrote:
> On 1/22/2023 3:46 AM, Tianyu Lan wrote:
>> From: Tianyu Lan <tiala@microsoft.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.