linux-kernel - RE: [PATCH] fix x2apic defect that Linux kernel doesn't mask 8259A interrupt during the time window between changing VT-d table base address and initializing these VT-d entries(smpboot.c and apic.c )

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Date:	Mon, 08 Oct 2012 16:57:13 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	"Zhang, Lin-Bao (Linux Kernel R&D)" <linbao.zhang@...com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alan@...rguk.ukuu.org.uk" <alan@...rguk.ukuu.org.uk>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"Croxon, Nigel" <nigel.croxon@...com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"Sakkinen, Jarkko" <jarkko.sakkinen@...el.com>,
	"joerg.roedel@....com" <joerg.roedel@....com>,
	"agordeev@...hat.com" <agordeev@...hat.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"stable@...nel.org" <stable@...nel.org>
Subject: RE: [PATCH] fix x2apic defect that Linux kernel doesn't mask 8259A
 interrupt during the time window between changing VT-d table base address
 and initializing these VT-d entries(smpboot.c and apic.c )

On Sun, 2012-10-07 at 21:53 -0700, Zhang, Lin-Bao (Linux Kernel R&D)
wrote:
> Hi Suresh,
> Could you please update current status about these 2 files and patch?
> I am not sure if I have answered your questions , if not ,feel free to let me know.
> This is my first time to submit patch to LKML, so what should I do next step ?

As I mentioned earlier, the current design already ensures that all the
IO-APIC RTE's are masked between the time we enable interrupt-remapping
to the time when the IO-APIC RTE's are configured correctly.

So I looked at why you are seeing the problem with v2.6.32 but not with
the recent kernels. And I think I found out the reason.

2.6.32 kernel is missing this fix,
http://marc.info/?l=linux-acpi&m=126993666715081&w=2

commit 7716a5c4ff5f1f3dc5e9edcab125cbf7fceef0af
Author: Eric W. Biederman <ebiederm@...ssion.com>
Date:   Tue Mar 30 01:07:12 2010 -0700

    x86, ioapic: Move nr_ioapic_registers calculation to mp_register_ioapic.
    
    Now that all ioapic registration happens in mp_register_ioapic we can
    move the calculation of nr_ioapic_registers there from enable_IO_APIC.
    The number of ioapic registers is already calucated in mp_register_ioapic
    so all that really needs to be done is to save the caluclated value
    in nr_ioapic_registers.
    
    Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
    LKML-Reference: <1269936436-7039-11-git-send-email-ebiederm@...ssion.com>
    Signed-off-by: H. Peter Anvin <hpa@...or.com>


Because of this, in v2.6.32, mask_IO_APIC_setup() is not working as
expected as nr_ioapic_registers[] are not yet initialized and thus the
io-apic RTE's are not masked as expected.

We just need the last hunk of that patch, I think.

Can you please apply the appended patch to 2.6.32 kernel and see if the
issue you mentioned gets fixed? If so, we can ask the -stable and OSV's
teams to pick up this fix.

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index f807255..dae9240 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -4293,6 +4281,7 @@ static int bad_ioapic(unsigned long address)
 void __init mp_register_ioapic(int id, u32 address, u32 gsi_base)
 {
 	int idx = 0;
+	int entries;
 
 	if (bad_ioapic(address))
 		return;
@@ -4311,9 +4300,14 @@ void __init mp_register_ioapic(int id, u32 address, u32 gsi_base)
 	 * Build basic GSI lookup table to facilitate gsi->io_apic lookups
 	 * and to prevent reprogramming of IOAPIC pins (PCI GSIs).
 	 */
+	entries = io_apic_get_redir_entries(idx);
 	mp_gsi_routing[idx].gsi_base = gsi_base;
-	mp_gsi_routing[idx].gsi_end = gsi_base +
-	    io_apic_get_redir_entries(idx) - 1;
+	mp_gsi_routing[idx].gsi_end = gsi_base + entries - 1;
+
+	/*
+	 * The number of IO-APIC IRQ registers (== #pins):
+	 */
+	nr_ioapic_registers[idx] = entries;
 
 	if (mp_gsi_routing[idx].gsi_end > gsi_end)
 		gsi_end = mp_gsi_routing[idx].gsi_end;


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