Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
Date:   Thu, 2 Nov 2023 13:36:49 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To:     "Nikunj A. Dadhania" <nikunj@amd.com>
Cc:     Tom Lendacky <thomas.lendacky@amd.com>,
        linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org,
        bp@alien8.de, mingo@redhat.com, tglx@linutronix.de,
        dave.hansen@linux.intel.com, dionnaglaze@google.com,
        pgonda@google.com, seanjc@google.com, pbonzini@redhat.com
Subject: Re: [PATCH v5 09/14] x86/sev: Add Secure TSC support for SNP guests
Message-ID: <20231102103649.3lsl25vqdquwequd@box.shutemov.name>
References: <20231030063652.68675-1-nikunj@amd.com>
 <20231030063652.68675-10-nikunj@amd.com>
 <b5e71977-abf6-aa27-3a7b-37230b014724@amd.com>
 <55de810b-66f9-49e3-8459-b7cac1532a0c@amd.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <55de810b-66f9-49e3-8459-b7cac1532a0c@amd.com>
Precedence: bulk

On Thu, Nov 02, 2023 at 11:11:52AM +0530, Nikunj A. Dadhania wrote:
> On 10/31/2023 1:56 AM, Tom Lendacky wrote:
> >> diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
> >> index cb0d6cd1c12f..e081ca4d5da2 100644
> >> --- a/include/linux/cc_platform.h
> >> +++ b/include/linux/cc_platform.h
> >> @@ -90,6 +90,14 @@ enum cc_attr {
> >> ?????? * Examples include TDX Guest.
> >> ?????? */
> >> ????? CC_ATTR_HOTPLUG_DISABLED,
> >> +
> >> +??? /**
> >> +???? * @CC_ATTR_GUEST_SECURE_TSC: Secure TSC is active.
> >> +???? *
> >> +???? * The platform/OS is running as a guest/virtual machine and actively
> >> +???? * using AMD SEV-SNP Secure TSC feature.
> > 
> > I think TDX also has a secure TSC like feature, so can this be generic?
> 
> Yes, we can do that. In SNP case SecureTSC is an optional feature, not sure if that is the case for TDX as well.
> 
> Kirill any inputs ?

We have several X86_FEATURE_ flags to indicate quality of TSC. Do we
really need a CC_ATTR on top of that? Maybe SEV code could just set
X86_FEATURE_ according to what its TSC can do?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov