From 1e77caec6dd1fefeb3bb3038e4c5f483c5f1722d Mon Sep 17 00:00:00 2001 From: Eduardo Habkost <ehabkost@redhat.com> Date: Mon, 5 Oct 2009 14:32:47 -0300 Subject: [PATCH 6/6] KVM: Fix task switch back link handling (v2, including save_state_to_tss16()) RH-Author: Eduardo Habkost <ehabkost@redhat.com> Message-id: <20091002161412.GE5106@blackpad.lan.raisama.net> Patchwork-id: 3557 O-Subject: [RHEL-5.4.z KVM PATCH] KVM: Fix task switch back link handling (v2, including save_state_to_tss16()) Bugzilla: 517324 RH-Acked-by: Juan Quintela <quintela@redhat.com> RH-Acked-by: Markus Armbruster <armbru@redhat.com> RH-Acked-by: Gleb Natapov <gleb@redhat.com> Bugzilla: https://bugzilla.redhat.com/517324 RH-Upstream-status: backport-from-upstream This backport includes two upstream commits: commit b237ac37a149e8b56436fabf093532483bff13b0 Author: Gleb Natapov <gleb@redhat.com> Date: Mon Mar 30 16:03:24 2009 +0300 KVM: Fix task switch back link handling. Back link is written to a wrong TSS now. Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com> and: commit 03c7e94f47cab5679125050cebf2663477b5670c Author: Juan Quintela <quintela@redhat.com> Date: Wed Sep 30 17:39:07 2009 +0200 KVM: remove pre_task_link setting in save_state_to_tss16 Now, also remove pre_task_link setting in save_state_to_tss16. commit b237ac37a149e8b56436fabf093532483bff13b0 Author: Gleb Natapov <gleb@redhat.com> Date: Mon Mar 30 16:03:24 2009 +0300 KVM: Fix task switch back link handling. CC: Gleb Natapov <gleb@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> --- arch/x86/kvm/x86.c | 41 ++++++++++++++++++++++++++++++++--------- 1 files changed, 32 insertions(+), 9 deletions(-) Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> --- arch/x86/kvm/x86.c | 41 ++++++++++++++++++++++++++++++++--------- 1 files changed, 32 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c2c9d52..8993f42 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3620,7 +3620,6 @@ static void save_state_to_tss32(struct kvm_vcpu *vcpu, tss->fs = get_segment_selector(vcpu, VCPU_SREG_FS); tss->gs = get_segment_selector(vcpu, VCPU_SREG_GS); tss->ldt_selector = get_segment_selector(vcpu, VCPU_SREG_LDTR); - tss->prev_task_link = get_segment_selector(vcpu, VCPU_SREG_TR); } static int load_state_from_tss32(struct kvm_vcpu *vcpu, @@ -3682,7 +3681,6 @@ static void save_state_to_tss16(struct kvm_vcpu *vcpu, tss->ss = get_segment_selector(vcpu, VCPU_SREG_SS); tss->ds = get_segment_selector(vcpu, VCPU_SREG_DS); tss->ldt = get_segment_selector(vcpu, VCPU_SREG_LDTR); - tss->prev_task_link = get_segment_selector(vcpu, VCPU_SREG_TR); } static int load_state_from_tss16(struct kvm_vcpu *vcpu, @@ -3717,8 +3715,8 @@ static int load_state_from_tss16(struct kvm_vcpu *vcpu, } static int kvm_task_switch_16(struct kvm_vcpu *vcpu, u16 tss_selector, - u32 old_tss_base, - struct desc_struct *nseg_desc) + u16 old_tss_sel, u32 old_tss_base, + struct desc_struct *nseg_desc) { struct tss_segment_16 tss_segment_16; int ret = 0; @@ -3737,6 +3735,16 @@ static int kvm_task_switch_16(struct kvm_vcpu *vcpu, u16 tss_selector, &tss_segment_16, sizeof tss_segment_16)) goto out; + if (old_tss_sel != 0xffff) { + tss_segment_16.prev_task_link = old_tss_sel; + + if (kvm_write_guest(vcpu->kvm, + get_tss_base_addr(vcpu, nseg_desc), + &tss_segment_16.prev_task_link, + sizeof tss_segment_16.prev_task_link)) + goto out; + } + if (load_state_from_tss16(vcpu, &tss_segment_16)) goto out; @@ -3746,7 +3754,7 @@ out: } static int kvm_task_switch_32(struct kvm_vcpu *vcpu, u16 tss_selector, - u32 old_tss_base, + u16 old_tss_sel, u32 old_tss_base, struct desc_struct *nseg_desc) { struct tss_segment_32 tss_segment_32; @@ -3766,6 +3774,16 @@ static int kvm_task_switch_32(struct kvm_vcpu *vcpu, u16 tss_selector, &tss_segment_32, sizeof tss_segment_32)) goto out; + if (old_tss_sel != 0xffff) { + tss_segment_32.prev_task_link = old_tss_sel; + + if (kvm_write_guest(vcpu->kvm, + get_tss_base_addr(vcpu, nseg_desc), + &tss_segment_32.prev_task_link, + sizeof tss_segment_32.prev_task_link)) + goto out; + } + if (load_state_from_tss32(vcpu, &tss_segment_32)) goto out; @@ -3821,12 +3839,17 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason) kvm_x86_ops->skip_emulated_instruction(vcpu); + /* set back link to prev task only if NT bit is set in eflags + note that old_tss_sel is not used afetr this point */ + if (reason != TASK_SWITCH_CALL && reason != TASK_SWITCH_GATE) + old_tss_sel = 0xffff; + if (nseg_desc.type & 8) - ret = kvm_task_switch_32(vcpu, tss_selector, old_tss_base, - &nseg_desc); + ret = kvm_task_switch_32(vcpu, tss_selector, old_tss_sel, + old_tss_base, &nseg_desc); else - ret = kvm_task_switch_16(vcpu, tss_selector, old_tss_base, - &nseg_desc); + ret = kvm_task_switch_16(vcpu, tss_selector, old_tss_sel, + old_tss_base, &nseg_desc); if (reason == TASK_SWITCH_CALL || reason == TASK_SWITCH_GATE) { u32 eflags = kvm_x86_ops->get_rflags(vcpu); -- 1.6.3.rc4.29.g8146