From: Jan Beulich <jbeulich@suse.com>
To: "Roger Pau Monné" <royger@FreeBSD.org>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>,
Ian Jackson <iwj@xenproject.org>
Subject: Re: [PATCH v2 1/6][4.16?] x86/x2APIC: defer probe until after IOMMU ACPI table parsing
Date: Mon, 8 Nov 2021 10:54:28 +0100 [thread overview]
Message-ID: <05d06abc-e52f-4e8a-8999-950712ce5508@suse.com> (raw)
In-Reply-To: <YYjvmy3BCnogsaBL@Air-de-Roger>
On 08.11.2021 10:36, Roger Pau Monné wrote:
> On Mon, Nov 08, 2021 at 08:40:59AM +0100, Jan Beulich wrote:
>> On 05.11.2021 16:38, Roger Pau Monné wrote:
>>> On Fri, Nov 05, 2021 at 01:32:18PM +0100, Jan Beulich wrote:
>>>> --- a/xen/arch/x86/setup.c
>>>> +++ b/xen/arch/x86/setup.c
>>>> @@ -1699,6 +1699,13 @@ void __init noreturn __start_xen(unsigne
>>>>
>>>> dmi_scan_machine();
>>>>
>>>> + /*
>>>> + * IOMMU-related ACPI table parsing has to happen before APIC probing, for
>>>> + * check_x2apic_preenabled() to be able to observe respective findings, in
>>>> + * particular iommu_intremap having got turned off.
>>>> + */
>>>> + acpi_iommu_init();
>>>
>>> If we pull this out I think we should add a check for acpi_disabled
>>> and if set turn off iommu_intremap and iommu_enable?
>>
>> Hmm, I should have added a note regarding this. If we want to exactly
>> retain prior behavior, acpi_ht would also need checking. Yet that has
>> gone wrong long ago: We parse way too many tables when acpi_disabled
>> && acpi_ht, and hence while correct wrt to prior behavior I'd consider
>> it wrong to (re)add a "!acpi_ht" check.
>>
>> As a result I'm of the opinion that checking acpi_disabled here also
>> isn't necessarily appropriate, and instead IOMMU disabling would
>> better be solely under the control of "iommu=".
>
> I haven't looked very deeply, but will the acpi helpers work correctly
> in that case? As acpi_boot_table_init will be short-circuited if
> `acpi_disabled && !acpi_ht`.
Oh, that's a good point you make.
Jan
next prev parent reply other threads:[~2021-11-08 9:54 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-05 12:30 [PATCH v2 0/6] x86: ACPI / APIC / IOMMU interaction Jan Beulich
2021-11-05 12:32 ` [PATCH v2 1/6][4.16?] x86/x2APIC: defer probe until after IOMMU ACPI table parsing Jan Beulich
2021-11-05 15:38 ` Roger Pau Monné
2021-11-05 15:47 ` Ian Jackson
2021-11-08 7:44 ` Jan Beulich
2021-11-08 15:04 ` Ian Jackson
2021-11-08 15:13 ` Jan Beulich
2021-11-16 15:19 ` [PATCH v2 1/6][4.16?] x86/x2APIC: defer probe until after IOMMU ACPI table parsing [and 2 more messages] Ian Jackson
2021-11-08 7:40 ` [PATCH v2 1/6][4.16?] x86/x2APIC: defer probe until after IOMMU ACPI table parsing Jan Beulich
2021-11-08 9:36 ` Roger Pau Monné
2021-11-08 9:54 ` Jan Beulich [this message]
2021-11-05 12:34 ` [PATCH v2 2/6] x86/APIC: drop clustered_apic_check() hook Jan Beulich
2021-11-08 11:02 ` Roger Pau Monné
2021-11-08 11:17 ` Jan Beulich
2021-11-05 12:34 ` [PATCH v2 3/6] x86/APIC: drop {acpi_madt,mps}_oem_check() hooks Jan Beulich
2021-11-05 12:34 ` [PATCH v2 4/6] x86/APIC: drop probe_default() Jan Beulich
2021-11-05 12:35 ` [PATCH v2 5/6] x86/APIC: rename cmdline_apic Jan Beulich
2021-11-05 12:35 ` [PATCH v2 6/6] x86/ACPI: drop dead interpreter-related code Jan Beulich
2021-11-08 11:40 ` [PATCH v2.1 1/6][4.16?] x86/x2APIC: defer probe until after IOMMU ACPI table parsing Jan Beulich
2021-11-08 11:54 ` Roger Pau Monné
2021-11-15 12:06 ` Jan Beulich
2021-11-15 14:31 ` [PATCH v2.2 " Jan Beulich
2021-11-15 15:07 ` Roger Pau Monné
2021-11-15 16:10 ` Jan Beulich
2021-11-16 11:44 ` Roger Pau Monné
2021-11-16 12:09 ` [PATCH v2 0/6] x86: ACPI / APIC / IOMMU interaction Andrew Cooper
2021-11-16 14:20 ` Jan Beulich
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