From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: [patch] KVM: always reload segment selectors Date: Sun, 11 Mar 2007 13:52:33 +0100 Message-ID: <20070311125233.GA17328@elte.hu> References: <20070311122441.GA10774@elte.hu> <45F3F85D.7000509@qumranet.com> <20070311124146.GA15115@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <20070311124146.GA15115-X9Un+BFzKDI@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Subject: [patch] KVM: always reload segment selectors From: Ingo Molnar failed VM entry on VMX might still change %fs or %gs, thus make sure that KVM always reloads the segment selectors. This is crutial on both x86 and x86_64: x86 has __KERNEL_PDA in %fs on which things like 'current' depends and x86_64 has 0 there and needs MSR_GS_BASE to work. Signed-off-by: Ingo Molnar --- drivers/kvm/vmx.c | 37 +++++++++++++++++++++---------------- 1 file changed, 21 insertions(+), 16 deletions(-) Index: linux/drivers/kvm/vmx.c =================================================================== --- linux.orig/drivers/kvm/vmx.c +++ linux/drivers/kvm/vmx.c @@ -1896,6 +1896,27 @@ again: [cr2]"i"(offsetof(struct kvm_vcpu, cr2)) : "cc", "memory" ); + /* + * Reload segment selectors ASAP. (it's needed for a functional + * kernel: x86 relies on having __KERNEL_PDA in %fs and x86_64 + * relies on having 0 in %gs for the CPU PDA to work.) + */ + if (fs_gs_ldt_reload_needed) { + load_ldt(ldt_sel); + load_fs(fs_sel); + /* + * If we have to reload gs, we must take care to + * preserve our gs base. + */ + local_irq_disable(); + load_gs(gs_sel); +#ifdef CONFIG_X86_64 + wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE)); +#endif + local_irq_enable(); + + reload_tss(); + } ++kvm_stat.exits; save_msrs(vcpu->guest_msrs, NR_BAD_MSRS); @@ -1913,22 +1934,6 @@ again: kvm_run->exit_reason = vmcs_read32(VM_INSTRUCTION_ERROR); r = 0; } else { - if (fs_gs_ldt_reload_needed) { - load_ldt(ldt_sel); - load_fs(fs_sel); - /* - * If we have to reload gs, we must take care to - * preserve our gs base. - */ - local_irq_disable(); - load_gs(gs_sel); -#ifdef CONFIG_X86_64 - wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE)); -#endif - local_irq_enable(); - - reload_tss(); - } /* * Profile KVM exit RIPs: */ ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV