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Message-ID: <608b37dbc59a80d32719c8fde8b6979a2b839e10.camel@intel.com>
Date: Wed, 27 Mar 2024 08:08:14 +0000
From: "Kang, Shan" <shan.kang@...el.com>
To: "Li, Xin3" <xin3.li@...el.com>, "kvm@...r.kernel.org"
<kvm@...r.kernel.org>, "linux-doc@...r.kernel.org"
<linux-doc@...r.kernel.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "linux-kselftest@...r.kernel.org"
<linux-kselftest@...r.kernel.org>
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<ravi.v.shankar@...el.com>, "xin@...or.com" <xin@...or.com>
Subject: Re: [PATCH v2 00/25] Enable FRED with KVM VMX
On Wed, 2024-02-07 at 09:26 -0800, Xin Li wrote:
> This patch set enables the Intel flexible return and event delivery
> (FRED) architecture with KVM VMX to allow guests to utilize FRED.
>
We tested this FRED KVM patch set on a 7th Intel(R) Core(TM) CPU and the Intel
Simics® Simulator with the following four configurations:
The first config is the baseline on bare metal.
The second config is the baseline on Intel Simics® Simulator.
The third config enables host FRED, but disables guest FRED.
The last config enables both host and guest FRED.
Following are the Kselftest results on KVM guests.
+---------------------------------------------+-------+-------+-------+-------+
| Config | Pass | Fail | Skip | Hang |
+---------------------------------------------+-------+-------+-------+-------+
|the 7th Intel(R) Core(TM) CPU | | | | |
| L0: 6.8.0-rc3+ w/ FRED native/KVM patch set| 1775 | 526 | 332 | 6 |
| L1: 6.8.0-rc3+ | | | | |
+---------------------------------------------+-------+-------+-------+-------+
|Intel Simics® Simulator w/o FRED model | | | | |
| L0: 6.8.0-rc3+ w/ FRED native/KVM patch set| 1770 | 526 | 331 | 12 |
| L1: 6.8.0-rc3+ w/ FRED native/KVM patch set| | | | |
+---------------------------------------------+-------+-------+-------+-------+
|Intel Simics® Simulator w/ FRED model | | | | |
| L0: 6.8.0-rc3+ w/ FRED native/KVM patch set| 1770 | 526 | 331 | 12 |
| L1: 6.8.0-rc3+ w/ FRED native/KVM patch set| | | | |
| but FRED disabled | | | | |
+---------------------------------------------+-------+-------+-------+-------+
|Intel Simics® Simulator w/ FRED model | | | | |
| L0: 6.8.0-rc3+ w/ FRED native/KVM patch set| 1769 | 528 | 330 | 12 |
| L1: 6.8.0-rc3+ w/ FRED native/KVM patch set| | | | |
+---------------------------------------------+-------+-------+-------+-------+
First of all we don't see any major issue. One major differences come from
perf tests. Another variances are from timer tests due to Intel Simics®
emulator's slowness.
The tests "x86:sysret_rip_64" and "x86:sigreturn_32" fail on the last config,
because they are not valid tests for FRED:
https://lore.kernel.org/lkml/20230220030959.119222-1-ammarfaizi2@gnuweeb.org/T/#u
https://lore.kernel.org/lkml/20230706052231.2183-1-xin3.li@intel.com/
NB: Some tests pass on Intel Simics® emulator, but not bare metal. If needed,
we can share the data.
We conducted local live migration tests with LKGS/FRED/WRMSRNS enabled/disabled
on Intel Simics® Simulator, and see no problems.
We also tested KVM Kselftest on a nested FRED KVM guest, 48 out of 83 cases
passed and the rest cases failed due to the slowness of Intel Simics® emulator.
Detailed report upon request.
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