linux-kernel - Re: [PATCH v4 3/3] irqchip/gic-v3: Enable non-coherent redistributors/ITSes ACPI probing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date: Mon, 22 Jan 2024 18:27:09 +0000
From: Marc Zyngier <maz@...nel.org>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	Robin Murphy <robin.murphy@....com>,
	Mark Rutland <mark.rutland@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-acpi@...r.kernel.org,
	acpica-devel@...ts.linux.dev,
	Fang Xiang <fangxiang3@...omi.com>,
	Robert Moore <robert.moore@...el.com>
Subject: Re: [PATCH v4 3/3] irqchip/gic-v3: Enable non-coherent redistributors/ITSes ACPI probing

On Mon, 22 Jan 2024 16:18:04 +0000,
Lorenzo Pieralisi <lpieralisi@...nel.org> wrote:
> 
> On Wed, Dec 27, 2023 at 12:00:38PM +0100, Lorenzo Pieralisi wrote:
> 
> [...]
> 
> > @@ -2380,6 +2385,10 @@ gic_acpi_parse_madt_gicc(union acpi_subtable_headers *header,
> >  		return -ENOMEM;
> >  	gic_request_region(gicc->gicr_base_address, size, "GICR");
> >  
> > +	if (gic_acpi_non_coherent_flag(gicc->flags,
> > +				       ACPI_MADT_GICC_NON_COHERENT))
> > +		gic_data.rdists.flags |= RDIST_FLAGS_FORCE_NON_SHAREABLE;
> > +
> 
> Quick question before reposting it. We run this function for
> every GICC entry, I didn't add a check to make sure all GICC
> entries have the same flag value, please let me know if that's
> OK.
> 
> I don't think there is a point in keeping a live variable across
> calls to set the flag once for all either.

I don't think that's useful. Once we see the flag being set, we'll
enforce the non-coherency. If it wasn't set before, it's because it
wasn't necessary.

If one day we find a firmware that only randomly exposes the flag,
we'll treat it as a quirk.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.