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authorRoman Kagan <rkagan@virtuozzo.com>2019-10-10 12:33:05 +0000
committerThomas Gleixner <tglx@linutronix.de>2019-10-15 10:57:09 +0200
commite211288b72f15259da86eed6eca680758dbe9e74 (patch)
treeea69ba8d1b056a0fbae6647504cd3eba4fde8a3f
parent1869dbe87cb94dc9a218ae1d9301dea3678bd4ff (diff)
x86/hyperv: Make vapic support x2apic mode
Now that there's Hyper-V IOMMU driver, Linux can switch to x2apic mode when supported by the vcpus. However, the apic access functions for Hyper-V enlightened apic assume xapic mode only. As a result, Linux fails to bring up secondary cpus when run as a guest in QEMU/KVM with both hv_apic and x2apic enabled. According to Michael Kelley, when in x2apic mode, the Hyper-V synthetic apic MSRs behave exactly the same as the corresponding architectural x2apic MSRs, so there's no need to override the apic accessors. The only exception is hv_apic_eoi_write, which benefits from lazy EOI when available; however, its implementation works for both xapic and x2apic modes. Fixes: 29217a474683 ("iommu/hyper-v: Add Hyper-V stub IOMMU driver") Fixes: 6b48cb5f8347 ("X86/Hyper-V: Enlighten APIC access") Suggested-by: Michael Kelley <mikelley@microsoft.com> Signed-off-by: Roman Kagan <rkagan@virtuozzo.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Reviewed-by: Michael Kelley <mikelley@microsoft.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20191010123258.16919-1-rkagan@virtuozzo.com
-rw-r--r--arch/x86/hyperv/hv_apic.c20
1 files changed, 15 insertions, 5 deletions
diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index 5c056b8aebef..e01078e93dd3 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -260,11 +260,21 @@ void __init hv_apic_init(void)
}
if (ms_hyperv.hints & HV_X64_APIC_ACCESS_RECOMMENDED) {
- pr_info("Hyper-V: Using MSR based APIC access\n");
+ pr_info("Hyper-V: Using enlightened APIC (%s mode)",
+ x2apic_enabled() ? "x2apic" : "xapic");
+ /*
+ * With x2apic, architectural x2apic MSRs are equivalent to the
+ * respective synthetic MSRs, so there's no need to override
+ * the apic accessors. The only exception is
+ * hv_apic_eoi_write, because it benefits from lazy EOI when
+ * available, but it works for both xapic and x2apic modes.
+ */
apic_set_eoi_write(hv_apic_eoi_write);
- apic->read = hv_apic_read;
- apic->write = hv_apic_write;
- apic->icr_write = hv_apic_icr_write;
- apic->icr_read = hv_apic_icr_read;
+ if (!x2apic_enabled()) {
+ apic->read = hv_apic_read;
+ apic->write = hv_apic_write;
+ apic->icr_write = hv_apic_icr_write;
+ apic->icr_read = hv_apic_icr_read;
+ }
}
}