linux-kernel - Re: [RFC PATCH V6 02/14] x86/sev: Add Check of #HV event in path

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Date:   Wed, 17 May 2023 17:55:45 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     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, 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, pangupta@....com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH V6 02/14] x86/sev: Add Check of #HV event in path

On 5/16/2023 5:32 PM, Peter Zijlstra wrote:
>> --- a/arch/x86/entry/entry_64.S
>> +++ b/arch/x86/entry/entry_64.S
>> @@ -1019,6 +1019,15 @@ SYM_CODE_END(paranoid_entry)
>>    * R15 - old SPEC_CTRL
>>    */
>>   SYM_CODE_START_LOCAL(paranoid_exit)
>> +#ifdef CONFIG_AMD_MEM_ENCRYPT
>> +	/*
>> +	 * If a #HV was delivered during execution and interrupts were
>> +	 * disabled, then check if it can be handled before the iret
>> +	 * (which may re-enable interrupts).
>> +	 */
>> +	mov     %rsp, %rdi
>> +	call    check_hv_pending
>> +#endif
>>   	UNWIND_HINT_REGS
>>   
>>   	/*
>> @@ -1143,6 +1152,15 @@ SYM_CODE_START(error_entry)
>>   SYM_CODE_END(error_entry)
>>   
>>   SYM_CODE_START_LOCAL(error_return)
>> +#ifdef CONFIG_AMD_MEM_ENCRYPT
>> +	/*
>> +	 * If a #HV was delivered during execution and interrupts were
>> +	 * disabled, then check if it can be handled before the iret
>> +	 * (which may re-enable interrupts).
>> +	 */
>> +	mov     %rsp, %rdi
>> +	call    check_hv_pending
>> +#endif
>>   	UNWIND_HINT_REGS
>>   	DEBUG_ENTRY_ASSERT_IRQS_OFF
>>   	testb	$3, CS(%rsp)
> Oh hell no... do now you're adding unconditional calls to every single
> interrupt and nmi exit path, with the grand total of 0 justification.
> 

Sorry to Add check inside of check_hv_pending(). Will move the check 
before calling check_hv_pending() in the next version. Thanks.