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