From ce69a784504222c3ab6f1b3c357d09ec5772127a Mon Sep 17 00:00:00 2001 From: Gleb Natapov Date: Mon, 20 Jul 2009 15:24:17 +0300 Subject: x86/apic: Enable x2APIC without interrupt remapping under KVM KVM would like to provide x2APIC interface to a guest without emulating interrupt remapping device. The reason KVM prefers guest to use x2APIC is that x2APIC interface is better virtualizable and provides better performance than mmio xAPIC interface: - msr exits are faster than mmio (no page table walk, emulation) - no need to read back ICR to look at the busy bit - one 64 bit ICR write instead of two 32 bit writes - shared code with the Hyper-V paravirt interface Included patch changes x2APIC enabling logic to enable it even if IR initialization failed, but kernel runs under KVM and no apic id is greater than 255 (if there is one spec requires BIOS to move to x2apic mode before starting an OS). -v2: fix build -v3: fix bug causing compiler warning Signed-off-by: Gleb Natapov Acked-by: Suresh Siddha Cc: Sheng Yang Cc: "avi@redhat.com" LKML-Reference: <20090720122417.GR5638@redhat.com> Signed-off-by: Ingo Molnar --- arch/x86/include/asm/apic.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'arch/x86/include/asm/apic.h') diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index bb7d47925847..586b7adb8e53 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -183,6 +183,10 @@ static inline int x2apic_enabled(void) } #define x2apic_supported() (cpu_has_x2apic) +static inline void x2apic_force_phys(void) +{ + x2apic_phys = 1; +} #else static inline void check_x2apic(void) { @@ -194,6 +198,9 @@ static inline int x2apic_enabled(void) { return 0; } +static inline void x2apic_force_phys(void) +{ +} #define x2apic_preenabled 0 #define x2apic_supported() 0 -- cgit v1.2.3