linux-kernel - Re: [RFC PATCH V5 15/15] x86/sev: Fix interrupt exit code paths from #HV exception

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Date:   Thu, 4 May 2023 15:41:13 -0700
From:   Tianyu Lan <ltykernel@...il.com>
To:     Tom Lendacky <thomas.lendacky@....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, venu.busireddy@...cle.com,
        sterritt@...gle.com, tony.luck@...el.com, samitolvanen@...gle.com,
        fenghua.yu@...el.com
Cc:     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 V5 15/15] x86/sev: Fix interrupt exit code paths from
 #HV exception

On 5/1/2023 9:02 AM, Tom Lendacky wrote:
>> From: Ashish Kalra <ashish.kalra@....com>
>>
>> Add checks in interrupt exit code paths in case of returns
>> to user mode to check if currently executing the #HV handler
>> then don't follow the irqentry_exit_to_user_mode path as
>> that can potentially cause the #HV handler to be
>> preempted and rescheduled on another CPU. Rescheduled #HV
>> handler on another cpu will cause interrupts to be handled
>> on a different cpu than the injected one, causing
>> invalid EOIs and missed/lost guest interrupts and
>> corresponding hangs and/or per-cpu IRQs handled on
>> non-intended cpu.
>>
>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> 
> This should be merged into one of the appropriate #HV patches and just 
> add Ashish with a Co-developed-by: tag where appropriate. This would be 
> appropriate as a separate only if discovered after the series was merged.

Sure. Will update in the next version.