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: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
---
arch/mips/include/asm/kvm_host.h | 2 +-
arch/mips/kernel/asm-offsets.c | 1 -
arch/mips/kernel/traps.c | 1 +
arch/mips/kvm/locore.S | 2 +-
arch/mips/kvm/mips.c | 3 ---
5 files changed, 3 insertions(+), 6 deletions(-)
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index f68293b4a598..24a8e557db88 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -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;
diff --git a/arch/mips/kernel/asm-offsets.c b/arch/mips/kernel/asm-offsets.c
index 420808899c70..a1263d188a5a 100644
--- a/arch/mips/kernel/asm-offsets.c
+++ b/arch/mips/kernel/asm-offsets.c
@@ -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);
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 4a1712b5abdf..66e5820bfdae 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -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];
diff --git a/arch/mips/kvm/locore.S b/arch/mips/kvm/locore.S
index 43c8ef847efa..f87bec546366 100644
--- a/arch/mips/kvm/locore.S
+++ b/arch/mips/kvm/locore.S
@@ -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
/*
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index c1ab6110ca1d..6e753761b5d6 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -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) {
--
2.4.10
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