From 91737ea205856c41183c2530fdb6b407ceeb3836 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Fri, 2 Dec 2016 23:40:52 +0000 Subject: [PATCH] KVM: MIPS/T&E: Reduce stale ASID checks MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The stale ASID checks taking place on VCPU load can be reduced: - Now that we check for a stale ASID on guest re-entry, there is no need to do so when loading the VCPU outside of guest context, since it will happen before entering the guest. Note that a lot of KVM VCPU ioctls will cause the VCPU to be loaded but guest context won't be entered. - There is no need to check for a stale kernel_mm ASID when the guest is in user mode and vice versa. In fact doing so can potentially be problematic since the user_mm ASID regeneration may trigger a new ASID cycle, which would cause the kern_mm ASID to become stale after it has been checked for staleness. Therefore only check the ASID for the mm corresponding to the current guest mode, and only if we're already in guest context. We drop some of the related kvm_debug() calls here too. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org --- arch/mips/kvm/trap_emul.c | 35 ++++++----------------------------- 1 file changed, 6 insertions(+), 29 deletions(-) diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c index 2b20b7d..edda8f0 100644 --- a/arch/mips/kvm/trap_emul.c +++ b/arch/mips/kvm/trap_emul.c @@ -714,35 +714,15 @@ static int kvm_trap_emul_vcpu_load(struct kvm_vcpu *vcpu, int cpu) struct mm_struct *user_mm = &vcpu->arch.guest_user_mm; struct mm_struct *mm; - /* Allocate new kernel and user ASIDs if needed */ - - if ((cpu_context(cpu, kern_mm) ^ asid_cache(cpu)) & - asid_version_mask(cpu)) { - get_new_mmu_context(kern_mm, cpu); - - kvm_debug("[%d]: cpu_context: %#lx\n", cpu, - cpu_context(cpu, current->mm)); - kvm_debug("[%d]: Allocated new ASID for Guest Kernel: %#lx\n", - cpu, cpu_context(cpu, kern_mm)); - } - - if ((cpu_context(cpu, user_mm) ^ asid_cache(cpu)) & - asid_version_mask(cpu)) { - get_new_mmu_context(user_mm, cpu); - - kvm_debug("[%d]: cpu_context: %#lx\n", cpu, - cpu_context(cpu, current->mm)); - kvm_debug("[%d]: Allocated new ASID for Guest User: %#lx\n", - cpu, cpu_context(cpu, user_mm)); - } - /* - * Were we in guest context? If so then the pre-empted ASID is - * no longer valid, we need to set it to what it should be based - * on the mode of the Guest (Kernel/User) + * Were we in guest context? If so, restore the appropriate ASID based + * on the mode of the Guest (Kernel/User). */ if (current->flags & PF_VCPU) { mm = KVM_GUEST_KERNEL_MODE(vcpu) ? kern_mm : user_mm; + if ((cpu_context(cpu, mm) ^ asid_cache(cpu)) & + asid_version_mask(cpu)) + get_new_mmu_context(mm, cpu); write_c0_entryhi(cpu_asid(cpu, mm)); TLBMISS_HANDLER_SETUP_PGD(mm->pgd); kvm_mips_suspend_mm(cpu); @@ -759,11 +739,8 @@ static int kvm_trap_emul_vcpu_put(struct kvm_vcpu *vcpu, int cpu) if (current->flags & PF_VCPU) { /* Restore normal Linux process memory map */ if (((cpu_context(cpu, current->mm) ^ asid_cache(cpu)) & - asid_version_mask(cpu))) { - kvm_debug("%s: Dropping MMU Context: %#lx\n", __func__, - cpu_context(cpu, current->mm)); + asid_version_mask(cpu))) get_new_mmu_context(current->mm, cpu); - } write_c0_entryhi(cpu_asid(cpu, current->mm)); TLBMISS_HANDLER_SETUP_PGD(current->mm->pgd); kvm_mips_resume_mm(cpu); -- 2.7.4