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From: Jason Andryuk <jason.andryuk@amd.com>
To: Roger Pau Monne <roger.pau@citrix.com>,
	<xen-devel@lists.xenproject.org>, <linux-kernel@vger.kernel.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	<Xenia.Ragiadakou@amd.com>, <Alejandro.GarciaVallejo@amd.com>,
	Juergen Gross <jgross@suse.com>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH] x86/xen: disable CPU idle and frequency drivers for PVH dom0
Date: Mon, 7 Apr 2025 10:13:50 -0400	[thread overview]
Message-ID: <99ad29b0-e57e-454e-b9b8-63b33f25ab45@amd.com> (raw)
In-Reply-To: <20250407101842.67228-1-roger.pau@citrix.com>

On 2025-04-07 06:18, Roger Pau Monne wrote:
> When running as a PVH dom0 the ACPI tables exposed to Linux are (mostly)
> the native ones, thus exposing the C and P states, that can lead to
> attachment of CPU idle and frequency drivers.  However the entity in
> control of the CPU C and P states is Xen, as dom0 doesn't have a full view
> of the system load, neither has all CPUs assigned and identity pinned.
> 
> Like it's done for classic PV guests, prevent Linux from using idle or
> frequency state drivers when running as a PVH dom0.
> 
> On an AMD EPYC 7543P system without this fix a Linux PVH dom0 will keep the
> host CPUs spinning at 100% even when dom0 is completely idle, as it's
> attempting to use the acpi_idle driver.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>

Thanks,
Jason

      reply	other threads:[~2025-04-07 14:13 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-04-07 10:18 Roger Pau Monne
2025-04-07 14:13 ` Jason Andryuk [this message]

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