From e7df56e4a00358b6975fae3b70dc9df1282d427a Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Wed, 14 Mar 2007 15:54:54 +0200 Subject: KVM: Remove extraneous guest entry on mmio read When emulating an mmio read, we actually emulate twice: once to determine the physical address of the mmio, and, after we've exited to userspace to get the mmio value, we emulate again to place the value in the result register and update any flags. But we don't really need to enter the guest again for that, only to take an immediate vmexit. So, if we detect that we're doing an mmio read, emulate a single instruction before entering the guest again. Signed-off-by: Avi Kivity --- drivers/kvm/kvm_main.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) (limited to 'drivers/kvm/kvm_main.c') diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c index cdf0b176851..f267dbb5284 100644 --- a/drivers/kvm/kvm_main.c +++ b/drivers/kvm/kvm_main.c @@ -1186,6 +1186,7 @@ int emulate_instruction(struct kvm_vcpu *vcpu, int r; int cs_db, cs_l; + vcpu->mmio_fault_cr2 = cr2; kvm_arch_ops->cache_regs(vcpu); kvm_arch_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l); @@ -1804,14 +1805,23 @@ static int kvm_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) r = complete_pio(vcpu); if (r) goto out; - } else { + } else if (!vcpu->mmio_is_write) { memcpy(vcpu->mmio_data, kvm_run->mmio.data, 8); vcpu->mmio_read_completed = 1; + vcpu->mmio_needed = 0; + r = emulate_instruction(vcpu, kvm_run, + vcpu->mmio_fault_cr2, 0); + if (r == EMULATE_DO_MMIO) { + /* + * Read-modify-write. Back to userspace. + */ + kvm_run->exit_reason = KVM_EXIT_MMIO; + r = 0; + goto out; + } } } - vcpu->mmio_needed = 0; - if (kvm_run->exit_reason == KVM_EXIT_HYPERCALL) { kvm_arch_ops->cache_regs(vcpu); vcpu->regs[VCPU_REGS_RAX] = kvm_run->hypercall.ret; -- cgit v1.2.3