On 14/07/2021 15:35, Andy Shevchenko wrote: > On Wed, Jul 14, 2021 at 3:56 PM Ralf Ramsauer > <ralf.ramsauer@xxxxxxxxxxxxxxxxx> wrote: >> On 14/07/2021 08:54, Jiri Slaby wrote: >>> On 13. 07. 21, 12:40, Andy Shevchenko wrote: > >>> Hmm, have you checked the commit which introduced the whitelist? >>> >>> Nevertheless, this needs to handled with care: while many 8250 devices >>> actually claim to support MSI(-X) interrupts it should not be >>> enabled be >>> default. I had at least one device in my hands with broken MSI >>> implementation. >>> >>> So better introduce a whitelist with devices that are known to support >>> MSI(-X) interrupts. I tested all devices mentioned in the patch. >>> >>> >>> You should have at least CCed the author for an input. >> >> Yep, back then I was testing three different 8250 pci cards. All of them >> claimed to support MSI, while one really worked with MSI, the one that I >> whitelisted. So I thought it would be better to use legacy IRQs as long >> as no one tested a specific card to work with MSI. > > Can you shed a light eventually what those cards are? So I found a no-name el-cheapo card that has some issues with MSI: 18:00.0 Serial controller: Device 1c00:3253 (rev 10) (prog-if 05 [16850]) The card comes with two serial lines. It comes perfectly up, if I enable it to use MSI in the whitelist: serial 0000:18:00.0: Using MSI(-X) interrupts serial 0000:18:00.0: Setup PCI port: port 40c0, irq 104, type 0 0000:18:00.0: ttyS6 at I/O 0x40c0 (irq = 104, base_baud = 115200) is a XR16850 serial 0000:18:00.0: Setup PCI port: port 40c8, irq 104, type 0 0000:18:00.0: ttyS7 at I/O 0x40c8 (irq = 104, base_baud = 115200) is a XR16850 After loading 8250_pci, lspci -vvs 18:0.0 tells: Capabilities: [68] MSI: Enable+ Count=1/32 Maskable+ 64bit+ Address: 00000000fee000b8 Data: 0000 Masking: ffffffff Pending: 00000000 Looks good so far. Now let's echo to the device. $ echo asdf > /dev/ttyS6 -- stuck. The echoing process stucks at close(): write(1, "asdf\n", 5) = 5 close(1 Stuck in the sense of: the echo is still killable, no crashes. The same happens if I try to access the device with stty. So something is odd here. However, the Netmos cards that I whitelisted do a great job. So I can't tell if I was just unlucky to grab a card that has issues with MSI, and this is an exception rather than the rule… HTH, Ralf > >> Don't do that… And don't convert it to a blacklist. A blacklist will >> break users until they report that something doesn't work. > > White list is not okay either. MSI in general is a right thing to do. > preventing users from MSI is asking for the performance degradation > and IRQ resource conflicts (in case the IRQ line is shared). > > Besides that, shouldn't it be rather the specific field in private (to > 8250_pci) structure than constantly growing list? >
