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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v5 5/6] xen/x86: add PHYSDEVOP_msi_control
On 19.07.2019 11:02, Roger Pau Monné wrote: > On Fri, Jul 19, 2019 at 08:04:45AM +0000, Jan Beulich wrote: >> On 18.07.2019 18:52, Roger Pau Monné wrote: >>> On Thu, Jul 18, 2019 at 03:17:27PM +0000, Jan Beulich wrote: >>>> On 18.07.2019 15:46, Roger Pau Monné wrote: >>>>> In fact I don't think INTx should be enabled when MSI(-X) is disabled, >>>>> QEMU already traps writes to the command register, and it will manage >>>>> INTx enabling/disabling by itself. I think the only check required is >>>>> that MSI(-X) cannot be enabled if INTx is also enabled. In the same >>>>> way both MSI caspabilities cannot be enabled simultaneously. The >>>>> function should not explicitly disable any of the other capabilities, >>>>> and just return -EBUSY if the caller attempts for example to enable >>>>> MSI while INTx or MSI-X is enabled. >>>> >>>> You do realize that pci_intx() only ever gets called for Xen >>>> internally used interrupts, i.e. mainly the serial console one? >>> >>> You will have to bear with me because I'm not sure I understand why >>> it does matter. Do you mean to point out that dom0 is the one in full >>> control of INTx, and thus Xen shouldn't care of whether INTx and >>> MSI(-X) are enabled at the same time? >>> >>> I still think that at least a warning should be printed if a caller >>> tries to enable MSI(-X) while INTx is also enabled, but unless there's >>> a reason to have both MSI(-X) and INTx enabled at the same time (maybe >>> a quirk for some hardware issue?) it shouldn't be allowed on this new >>> interface. >> >> I don't mind improvements to the current situation (i.e. such a >> warning may indeed make sense); I merely stated how things currently >> are. INTx treatment was completely left aside when MSI support was >> introduced into Xen. > > In order to give Marek a more concise reply, would you agree to return > -EBUSY (or some error code) and print a warning message if the caller > attempts to enable MSI(-X) while INTx is also enabled? As to returning an error - I think so, yes. I'm less sure about logging a message. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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