Messages in this thread | | | From | Thomas Gleixner <> | Subject | RE: [PATCH] x86/i8259: Work around buggy legacy PIC | Date | Fri, 14 May 2021 15:01:48 +0200 |
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David,
On Thu, May 13 2021 at 10:36, David Laight wrote:
>> -----Original Message----- >> From: Maximilian Luz <luzmaximilian@gmail.com> >> Sent: 13 May 2021 11:12 >> To: David Laight <David.Laight@ACULAB.COM>; Thomas Gleixner <tglx@linutronix.de>; Ingo Molnar >> <mingo@redhat.com>; Borislav Petkov <bp@alien8.de> >> Cc: H. Peter Anvin <hpa@zytor.com>; Sachi King <nakato@nakato.io>; x86@kernel.org; linux- >> kernel@vger.kernel.org; stable@vger.kernel.org >> Subject: Re: [PATCH] x86/i8259: Work around buggy legacy PIC
can you please fix your mail client and spare us the useless header duplication in the reply?
> It is also worth noting that the probe code is spectacularly crap. > It writes 0xff and then checks that 0xff is read back. > Almost anything (including a failed PCIe read to the ISA bridge) > will return 0xff and make the test pass.
unsigned char probe_val = ~(1 << PIC_CASCADE_IR);
outb(probe_val, PIC_MASTER_IMR); new_val = inb(PIC_MASTER_IMR);
How is that writing 0xFF?
Thanks,
tglx
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