Messages in this thread | | | Subject | Re: [RFC PATCH 1/1] platform-msi: Add platform check for subdevice irq domain | From | Lu Baolu <> | Date | Wed, 16 Dec 2020 09:48:03 +0800 |
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Hi Bjorn,
On 12/11/20 2:57 AM, Bjorn Helgaas wrote: > On Thu, Dec 10, 2020 at 08:46:24AM +0800, Lu Baolu wrote: >> The pci_subdevice_msi_create_irq_domain() should fail if the underlying >> platform is not able to support IMS (Interrupt Message Storage). Otherwise, >> the isolation of interrupt is not guaranteed. >> >> For x86, IMS is only supported on bare metal for now. We could enable it >> in the virtualization environments in the future if interrupt HYPERCALL >> domain is supported or the hardware has the capability of interrupt >> isolation for subdevices. > >> + * We want to figure out which context we are running in. But the hardware >> + * does not introduce a reliable way (instruction, CPUID leaf, MSR, whatever) >> + * which can be manipulated by the VMM to let the OS figure out where it runs. >> + * So we go with the below probably_on_bare_metal() function as a replacement >> + * for definitely_on_bare_metal() to go forward only for the very simple reason >> + * that this is the only option we have. >> + */ >> +static const char * const possible_vmm_vendor_name[] = { >> + "QEMU", "Bochs", "KVM", "Xen", "VMware", "VMW", "VMware Inc.", >> + "innotek GmbH", "Oracle Corporation", "Parallels", "BHYVE", >> + "Microsoft Corporation" >> +}; >> + >> +static bool probably_on_bare_metal(void) > > What is the point of a function called probably_on_bare_metal()? > *Probably*? The caller can't really do anything with the fact that > we're not 100% sure this gives the correct answer. Just call it > "on_bare_metal()" or something and accept the fact that it might be > wrong sometimes.
Agreed. we can use on_bare_metal() and add comments and kernel messages to let users and developers know that we're not 100% sure. People should help to make it more accurate by reporting exceptions.
> > This patch goes with IMS support, which somebody else is handling, so > I assume you don't need anything from the PCI side.
Yes. This is a followup of previous discussion.
Best regards, baolu
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