[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Fri, 2 Feb 2024 16:47:02 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
CC: <linux-pm@...r.kernel.org>, <loongarch@...ts.linux.dev>,
<linux-acpi@...r.kernel.org>, <linux-arch@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
<linux-riscv@...ts.infradead.org>, <kvmarm@...ts.linux.dev>,
<x86@...nel.org>, <acpica-devel@...ts.linuxfoundation.org>,
<linux-csky@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<linux-ia64@...r.kernel.org>, <linux-parisc@...r.kernel.org>, Salil Mehta
<salil.mehta@...wei.com>, Jean-Philippe Brucker <jean-philippe@...aro.org>,
<jianyong.wu@....com>, <justin.he@....com>, James Morse
<james.morse@....com>, "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH RFC v4 11/15] irqchip/gic-v3: Add support for ACPI's
disabled but 'online capable' CPUs
On Wed, 31 Jan 2024 16:50:32 +0000
Russell King (Oracle) <rmk+kernel@...linux.org.uk> wrote:
> From: James Morse <james.morse@....com>
>
> To support virtual CPU hotplug, ACPI has added an 'online capable' bit
> to the MADT GICC entries. This indicates a disabled CPU entry may not
> be possible to online via PSCI until firmware has set enabled bit in
> _STA.
>
> This means that a "usable" GIC is one that is marked as either enabled,
> or online capable. Therefore, change acpi_gicc_is_usable() to check both
> bits. However, we need to change the test in gic_acpi_match_gicc() back
> to testing just the enabled bit so the count of enabled distributors is
> correct.
>
> What about the redistributor in the GICC entry? ACPI doesn't want to say.
> Assume the worst: When a redistributor is described in the GICC entry,
> but the entry is marked as disabled at boot, assume the redistributor
> is inaccessible.
>
> The GICv3 driver doesn't support late online of redistributors, so this
> means the corresponding CPU can't be brought online either. Clear the
> possible and present bits.
>
> Systems that want CPU hotplug in a VM can ensure their redistributors
> are always-on, and describe them that way with a GICR entry in the MADT.
>
> When mapping redistributors found via GICC entries, handle the case
> where the arch code believes the CPU is present and possible, but it
> does not have an accessible redistributor. Print a warning and clear
> the present and possible bits.
>
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Powered by blists - more mailing lists