4.19-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit d2266bbfa9e3e32e3b642965088ca461bd24a94f ]
The "pciserial" earlyprintk variant helps much on many modern x86 platforms, but unfortunately there are still some platforms with PCI UART devices which have the wrong PCI class code. In that case, the current class code check does not allow for them to be used for logging.
Add a sub-option "force" which overrides the class code check and thus the use of such device can be enforced.
[ bp: massage formulations. ]
Suggested-by: Borislav Petkov bp@alien8.de Signed-off-by: Feng Tang feng.tang@intel.com Signed-off-by: Borislav Petkov bp@suse.de Cc: "H. Peter Anvin" hpa@zytor.com Cc: "Stuart R . Anderson" stuart.r.anderson@intel.com Cc: Bjorn Helgaas bhelgaas@google.com Cc: David Rientjes rientjes@google.com Cc: Feng Tang feng.tang@intel.com Cc: Frederic Weisbecker frederic@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: H Peter Anvin hpa@linux.intel.com Cc: Ingo Molnar mingo@kernel.org Cc: Jiri Kosina jkosina@suse.cz Cc: Jonathan Corbet corbet@lwn.net Cc: Kai-Heng Feng kai.heng.feng@canonical.com Cc: Kate Stewart kstewart@linuxfoundation.org Cc: Konrad Rzeszutek Wilk konrad.wilk@oracle.com Cc: Peter Zijlstra peterz@infradead.org Cc: Philippe Ombredanne pombredanne@nexb.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Thymo van Beers thymovanbeers@gmail.com Cc: alan@linux.intel.com Cc: linux-doc@vger.kernel.org Link: http://lkml.kernel.org/r/20181002164921.25833-1-feng.tang@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- .../admin-guide/kernel-parameters.txt | 6 +++- arch/x86/kernel/early_printk.c | 29 ++++++++++++------- 2 files changed, 24 insertions(+), 11 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 92eb1f42240d..34e6800dea0e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1063,7 +1063,7 @@ earlyprintk=serial[,0x...[,baudrate]] earlyprintk=ttySn[,baudrate] earlyprintk=dbgp[debugController#] - earlyprintk=pciserial,bus:device.function[,baudrate] + earlyprintk=pciserial[,force],bus:device.function[,baudrate] earlyprintk=xdbc[xhciController#]
earlyprintk is useful when the kernel crashes before @@ -1095,6 +1095,10 @@
The sclp output can only be used on s390.
+ The optional "force" to "pciserial" enables use of a + PCI device even when its classcode is not of the + UART class. + edac_report= [HW,EDAC] Control how to report EDAC event Format: {"on" | "off" | "force"} on: enable EDAC to report H/W event. May be overridden diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c index 5e801c8c8ce7..374a52fa5296 100644 --- a/arch/x86/kernel/early_printk.c +++ b/arch/x86/kernel/early_printk.c @@ -213,8 +213,9 @@ static unsigned int mem32_serial_in(unsigned long addr, int offset) * early_pci_serial_init() * * This function is invoked when the early_printk param starts with "pciserial" - * The rest of the param should be ",B:D.F,baud" where B, D & F describe the - * location of a PCI device that must be a UART device. + * The rest of the param should be "[force],B:D.F,baud", where B, D & F describe + * the location of a PCI device that must be a UART device. "force" is optional + * and overrides the use of an UART device with a wrong PCI class code. */ static __init void early_pci_serial_init(char *s) { @@ -224,17 +225,23 @@ static __init void early_pci_serial_init(char *s) u32 classcode, bar0; u16 cmdreg; char *e; + int force = 0;
- - /* - * First, part the param to get the BDF values - */ if (*s == ',') ++s;
if (*s == 0) return;
+ /* Force the use of an UART device with wrong class code */ + if (!strncmp(s, "force,", 6)) { + force = 1; + s += 6; + } + + /* + * Part the param to get the BDF values + */ bus = (u8)simple_strtoul(s, &e, 16); s = e; if (*s != ':') @@ -253,7 +260,7 @@ static __init void early_pci_serial_init(char *s) s++;
/* - * Second, find the device from the BDF + * Find the device from the BDF */ cmdreg = read_pci_config(bus, slot, func, PCI_COMMAND); classcode = read_pci_config(bus, slot, func, PCI_CLASS_REVISION); @@ -264,8 +271,10 @@ static __init void early_pci_serial_init(char *s) */ if (((classcode >> 16 != PCI_CLASS_COMMUNICATION_MODEM) && (classcode >> 16 != PCI_CLASS_COMMUNICATION_SERIAL)) || - (((classcode >> 8) & 0xff) != 0x02)) /* 16550 I/F at BAR0 */ - return; + (((classcode >> 8) & 0xff) != 0x02)) /* 16550 I/F at BAR0 */ { + if (!force) + return; + }
/* * Determine if it is IO or memory mapped @@ -289,7 +298,7 @@ static __init void early_pci_serial_init(char *s) }
/* - * Lastly, initialize the hardware + * Initialize the hardware */ if (*s) { if (strcmp(s, "nocfg") == 0)