From: "Kalra, Ashish" <ashish.kalra@amd.com>
To: Borislav Petkov <bp@alien8.de>, K Prateek Nayak <kprateek.nayak@amd.com>
Cc: tglx@kernel.org, mingo@redhat.com, dave.hansen@linux.intel.com,
x86@kernel.org, hpa@zytor.com, seanjc@google.com,
peterz@infradead.org, thomas.lendacky@amd.com,
herbert@gondor.apana.org.au, davem@davemloft.net,
ardb@kernel.org, pbonzini@redhat.com, aik@amd.com,
Michael.Roth@amd.com, Tycho.Andersen@amd.com,
Nathan.Fontenot@amd.com, ackerleytng@google.com,
jackyli@google.com, pgonda@google.com, rientjes@google.com,
jacobhxu@google.com, xin@zytor.com,
pawan.kumar.gupta@linux.intel.com, babu.moger@amd.com,
dyoung@redhat.com, nikunj@amd.com, john.allen@amd.com,
darwi@linutronix.de, linux-kernel@vger.kernel.org,
linux-crypto@vger.kernel.org, kvm@vger.kernel.org,
linux-coco@lists.linux.dev
Subject: Re: [PATCH v10 2/6] x86/sev: Initialize RMPOPT configuration MSRs
Date: Thu, 23 Jul 2026 01:50:48 -0500 [thread overview]
Message-ID: <5460b946-b511-4060-8951-264d17a2b21b@amd.com> (raw)
In-Reply-To: <20260723051422.GGamGjLhlTqRDcFlee@fat_crate.local>
Hello Boris,
On 7/23/2026 12:14 AM, Borislav Petkov wrote:
> On Thu, Jul 23, 2026 at 10:23:56AM +0530, K Prateek Nayak wrote:
>> The offline cores will remain offline since hotplug is disabled. RMPOPT
>> is simply a performance optimization for RMP checks and leaving the
>> offline cores (that will never exit idle) unoptimized should be
>> acceptable.
>
> What happens if you boot with a subset of cores, the boot flow enables RMPOPT
> and then you online the rest?
>
> Have we tried that?
>
It can't happen here. snp_prepare() does the following, in order:
1. cpu_hotplug_disable() — freeze the CPU set.
2. fail SNP init (-EOPNOTSUPP) unless every present CPU is online (cpumask_equal(cpu_online_mask, cpu_present_mask).
3. enable SNP.
snp_setup_rmpopt() runs only after snp_prepare() succeeds, so all present CPUs are online and stay online (hotplug is
disabled). No core's primary thread can be offline at this point.
(The kexec path is the one exception — snp_prepare() returns early there — which I'm handling in the other thread.)
Thanks,
Ashish
next prev parent reply other threads:[~2026-07-23 6:50 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-30 18:08 [PATCH v10 0/6] Add RMPOPT support Ashish Kalra
2026-06-30 18:09 ` [PATCH v10 1/6] x86/cpufeatures: Add X86_FEATURE_RMPOPT feature flag Ashish Kalra
2026-07-20 21:12 ` Borislav Petkov
2026-06-30 18:10 ` [PATCH v10 2/6] x86/sev: Initialize RMPOPT configuration MSRs Ashish Kalra
2026-07-20 22:17 ` Borislav Petkov
2026-07-20 22:38 ` Kalra, Ashish
2026-07-21 1:48 ` Borislav Petkov
2026-07-21 14:26 ` Kalra, Ashish
2026-07-21 14:57 ` K Prateek Nayak
2026-07-21 20:46 ` Kalra, Ashish
2026-07-22 2:46 ` K Prateek Nayak
2026-07-22 19:17 ` Kalra, Ashish
2026-07-21 15:32 ` Borislav Petkov
2026-07-23 1:10 ` Borislav Petkov
2026-07-23 4:53 ` K Prateek Nayak
2026-07-23 5:14 ` Borislav Petkov
2026-07-23 5:58 ` K Prateek Nayak
2026-07-23 7:03 ` Kalra, Ashish
2026-07-23 7:16 ` K Prateek Nayak
2026-07-23 8:00 ` Kalra, Ashish
2026-07-23 6:50 ` Kalra, Ashish [this message]
2026-07-23 13:24 ` Kalra, Ashish
2026-07-23 14:29 ` K Prateek Nayak
2026-07-23 18:32 ` Borislav Petkov
2026-06-30 18:11 ` [PATCH v10 3/6] x86/sev: Disable CPU hotplug while SNP is active Ashish Kalra
2026-07-01 9:40 ` Jethro Beekman
2026-07-01 16:39 ` K Prateek Nayak
2026-07-01 21:08 ` Kalra, Ashish
2026-07-01 21:25 ` Kalra, Ashish
2026-07-06 12:02 ` Jethro Beekman
2026-07-23 18:53 ` Borislav Petkov
2026-07-23 19:44 ` Kalra, Ashish
2026-07-23 20:00 ` Borislav Petkov
2026-07-23 20:39 ` Kalra, Ashish
2026-07-23 22:19 ` Kalra, Ashish
2026-06-30 18:11 ` [PATCH v10 4/6] x86/sev: Add support to perform RMP optimizations asynchronously Ashish Kalra
2026-07-21 15:06 ` K Prateek Nayak
2026-07-22 19:43 ` Kalra, Ashish
2026-06-30 18:11 ` [PATCH v10 5/6] x86/sev: Add interface to re-enable RMP optimizations Ashish Kalra
2026-06-30 18:12 ` [PATCH v10 6/6] KVM: SEV: Perform RMP optimizations on SNP guest shutdown Ashish Kalra
2026-07-20 20:17 ` [PATCH v10 0/6] Add RMPOPT support Kalra, Ashish
2026-07-20 20:28 ` Borislav Petkov
2026-07-20 20:39 ` Kalra, Ashish
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