On Tue, Jul 1, 2025 at 1:04 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > > On Tue, Jul 01 2025 at 12:00, Anup Patel wrote: > > On Mon, Jun 30, 2025 at 9:39 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > >> > When injecting IPIs to a set of harts, the IMSIC IPI support will > >> > do a separate MMIO write to SETIPNUM_LE register of each target > >> > hart. This means on a platform where IMSIC is trap-n-emulated, > >> > there will be N MMIO traps when injecting IPI to N target harts > >> > hence IPIs based on IMSIC software injected MSI is slow compared > >> > to the SBI IPI extension. > >> > > >> > Add a kernel parameter to disable IPIs in IMSIC driver for platforms > >> > with trap-n-emulated IMSIC. > >> > >> Why do you need a kernel parameter for that. If the platform uses trap-n > >> emulation, then disable the IPI muck automatically, no? > >> > > Unfortunately, we don't have DT, ACPI, or any other way of discovering > > whether underlying IMSIC is trap-n-emulated. In fact, the DT or ACPI > > passed to a KVM Guest is the same irrespective of whether underlying > > IMSIC is trap-n-emulated or backed by hardware IMSIC VS-file. > > Sigh. > > > Using software injected MSIs as IPIs is purely a software choice in the > > IMSIC driver so this new kernel parameter allows users to override it. > > Please add that information to the change log. > Okay, I will add these details to the patch description. Regards, Anup
