Commit 878edf01 authored by James Hogan's avatar James Hogan Committed by Paolo Bonzini
Browse files

MIPS: KVM: Restore host EBase from ebase variable 



The host kernel's exception vector base address is currently saved in
the VCPU structure at creation time, and restored on a guest exit.
However it doesn't change and can already be easily accessed from the
'ebase' variable (arch/mips/kernel/traps.c), so drop the host_ebase
member of kvm_vcpu_arch, export the 'ebase' variable to modules and load
from there instead.

This does result in a single extra instruction (lui) on the guest exit
path, but simplifies the code a bit and removes the redundant storage of
the host exception base address.

Credit for the idea goes to Cavium's VZ KVM implementation.

Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 26ee17ff

arch/mips/include/asm/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -334,7 +334,7 @@ struct kvm_mips_tlb { 


#define KVM_MIPS_GUEST_TLB_SIZE	64

struct kvm_vcpu_arch {

	void *host_ebase, *guest_ebase;

	void *guest_ebase;

	int (*vcpu_run)(struct kvm_run *run, struct kvm_vcpu *vcpu);

	unsigned long host_stack;

	unsigned long host_gp;

arch/mips/kernel/asm-offsets.c

+0 −1
Original line number Diff line number Diff line
@@ -355,7 +355,6 @@ void output_kvm_defines(void) 
	OFFSET(VCPU_RUN, kvm_vcpu, run);

	OFFSET(VCPU_HOST_ARCH, kvm_vcpu, arch);



	OFFSET(VCPU_HOST_EBASE, kvm_vcpu_arch, host_ebase);

	OFFSET(VCPU_GUEST_EBASE, kvm_vcpu_arch, guest_ebase);



	OFFSET(VCPU_HOST_STACK, kvm_vcpu_arch, host_stack);

arch/mips/kernel/traps.c

+1 −0
Original line number Diff line number Diff line
@@ -1859,6 +1859,7 @@ void __noreturn nmi_exception_handler(struct pt_regs *regs) 
#define VECTORSPACING 0x100	/* for EI/VI mode */



unsigned long ebase;

EXPORT_SYMBOL_GPL(ebase);

unsigned long exception_handlers[32];

unsigned long vi_handlers[64];

arch/mips/kvm/locore.S

+1 −1
Original line number Diff line number Diff line
@@ -319,7 +319,7 @@ NESTED (MIPSX(GuestException), CALLFRAME_SIZ, ra) 
	mtc0	k0, CP0_STATUS

	ehb



	LONG_L	k0, VCPU_HOST_EBASE(k1)

	LONG_L	k0, ebase

	mtc0	k0,CP0_EBASE



	/*

arch/mips/kvm/mips.c

+0 −3
Original line number Diff line number Diff line
@@ -273,9 +273,6 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id) 
	else

		size = 0x4000;



	/* Save Linux EBASE */

	vcpu->arch.host_ebase = (void *)read_c0_ebase();



	gebase = kzalloc(ALIGN(size, PAGE_SIZE), GFP_KERNEL);



	if (!gebase) {

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