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Subject: Re: [PATCH] Allow RDTSC and RDTSCP from userspace
To:     Dave Hansen <dave.hansen@intel.com>,
        Mike Stunes <mstunes@vmware.com>, joro@8bytes.org
Cc:     dan.j.williams@intel.com, dave.hansen@linux.intel.com,
        hpa@zytor.com, jgross@suse.com, jroedel@suse.de, jslaby@suse.cz,
        keescook@chromium.org, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, luto@kernel.org,
        peterz@infradead.org, thellstrom@vmware.com,
        virtualization@lists.linux-foundation.org, x86@kernel.org,
        Sean Christopherson <sean.j.christopherson@intel.com>
References: <20200319091407.1481-56-joro@8bytes.org>
 <20200424210316.848878-1-mstunes@vmware.com>
 <2c49061d-eb84-032e-8dcb-dd36a891ce90@intel.com>
From:   Tom Lendacky <thomas.lendacky@amd.com>
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Date:   Fri, 24 Apr 2020 16:27:32 -0500
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On 4/24/20 4:24 PM, Dave Hansen wrote:
> On 4/24/20 2:03 PM, Mike Stunes wrote:
>> I needed to allow RDTSC(P) from userspace and in early boot in order to
>> get userspace started properly. Patch below.
>>
>> ---
>> SEV-ES guests will need to execute rdtsc and rdtscp from userspace and
>> during early boot. Move the rdtsc(p) #VC handler into common code and
>> extend the #VC handlers.
> 
> Do SEV-ES guests _always_ #VC on rdtsc(p)?

Only if the hypervisor is intercepting those instructions.

Thanks,
Tom

>