[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] x86/x2apic: introduce a mixed physical/cluster mode
On Mon, Oct 30, 2023 at 04:27:22PM +0100, Roger Pau Monné wrote: > On Mon, Oct 30, 2023 at 07:50:27AM -0700, Elliott Mitchell wrote: > > On Tue, Oct 24, 2023 at 03:51:50PM +0200, Roger Pau Monne wrote: > > > diff --git a/xen/arch/x86/genapic/x2apic.c b/xen/arch/x86/genapic/x2apic.c > > > index 707deef98c27..15632cc7332e 100644 > > > --- a/xen/arch/x86/genapic/x2apic.c > > > +++ b/xen/arch/x86/genapic/x2apic.c > > > @@ -220,38 +239,56 @@ static struct notifier_block x2apic_cpu_nfb = { > > > static int8_t __initdata x2apic_phys = -1; > > > boolean_param("x2apic_phys", x2apic_phys); > > > > > > +enum { > > > + unset, physical, cluster, mixed > > > +} static __initdata x2apic_mode = unset; > > > + > > > +static int __init parse_x2apic_mode(const char *s) > > > +{ > > > + if ( !cmdline_strcmp(s, "physical") ) > > > + x2apic_mode = physical; > > > + else if ( !cmdline_strcmp(s, "cluster") ) > > > + x2apic_mode = cluster; > > > + else if ( !cmdline_strcmp(s, "mixed") ) > > > + x2apic_mode = mixed; > > > + else > > > + return EINVAL; > > > + > > > + return 0; > > > +} > > > +custom_param("x2apic-mode", parse_x2apic_mode); > > > + > > > const struct genapic *__init apic_x2apic_probe(void) > > > { > > > - if ( x2apic_phys < 0 ) > > > + /* x2apic-mode option has preference over x2apic_phys. */ > > > + if ( x2apic_phys >= 0 && x2apic_mode == unset ) > > > + x2apic_mode = x2apic_phys ? physical : cluster; > > > + > > > + if ( x2apic_mode == unset ) > > > { > > > - /* > > > - * Force physical mode if there's no (full) interrupt remapping > > > support: > > > - * The ID in clustered mode requires a 32 bit destination field > > > due to > > > - * the usage of the high 16 bits to hold the cluster ID. > > > - */ > > > - x2apic_phys = iommu_intremap != iommu_intremap_full || > > > - (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL) || > > > - IS_ENABLED(CONFIG_X2APIC_PHYSICAL); > > > - } > > > - else if ( !x2apic_phys ) > > > - switch ( iommu_intremap ) > > > + if ( acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL ) > > > { > > > > Could this explain the issues with recent AMD processors/motherboards? > > > > Mainly the firmware had been setting this flag, but Xen was previously > > ignoring it? > > No, not unless you pass {no-}x2apic_phys={false,0} on the Xen command > line to force logical (clustered) destination mode. > > > As such Xen had been attempting to use cluster mode on an > > x2APIC where that mode was broken for physical interrupts? > > No, not realy, x2apic_phys was already forced to true if > acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL is set on the FADT (I > just delete that line in this same chunk and move it here). I think I inverted the case in my speculation. Perhaps AMD's firmware SHOULD have been setting ACPI_FADT_APIC_PHYSICAL, but failed to? Given the rough launch with AMD's latest, I could readily see there being a goof like this. Question will then be, will mixed mode work on these processors? -- (\___(\___(\______ --=> 8-) EHM <=-- ______/)___/)___/) \BS ( | ehem+sigmsg@xxxxxxx PGP 87145445 | ) / \_CS\ | _____ -O #include <stddisclaimer.h> O- _____ | / _/ 8A19\___\_|_/58D2 7E3D DDF4 7BA6 <-PGP-> 41D1 B375 37D0 8714\_|_/___/5445
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