From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Nadav Har'El" Subject: [PATCH 08/31] nVMX: Fix local_vcpus_link handling Date: Mon, 16 May 2011 22:48:01 +0300 Message-ID: <201105161948.p4GJm1as001742@rice.haifa.ibm.com> References: <1305575004-nyh@il.ibm.com> Cc: gleb@redhat.com, avi@redhat.com To: kvm@vger.kernel.org Return-path: Received: from mtagate7.uk.ibm.com ([194.196.100.167]:53709 "EHLO mtagate7.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751013Ab1EPTsF (ORCPT ); Mon, 16 May 2011 15:48:05 -0400 Received: from d06nrmr1707.portsmouth.uk.ibm.com (d06nrmr1707.portsmouth.uk.ibm.com [9.149.39.225]) by mtagate7.uk.ibm.com (8.13.1/8.13.1) with ESMTP id p4GJm39W006686 for ; Mon, 16 May 2011 19:48:03 GMT Received: from d06av05.portsmouth.uk.ibm.com (d06av05.portsmouth.uk.ibm.com [9.149.37.229]) by d06nrmr1707.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p4GJm3lY1925282 for ; Mon, 16 May 2011 20:48:03 +0100 Received: from d06av05.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av05.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p4GJm2go021086 for ; Mon, 16 May 2011 13:48:03 -0600 Sender: kvm-owner@vger.kernel.org List-ID: In VMX, before we bring down a CPU we must VMCLEAR all VMCSs loaded on it because (at least in theory) the processor might not have written all of its content back to memory. Since a patch from June 26, 2008, this is done using a per-cpu "vcpus_on_cpu" linked list of vcpus loaded on each CPU. The problem is that with nested VMX, we no longer have the concept of a vcpu being loaded on a cpu: A vcpu has multiple VMCSs (one for L1, a pool for L2s), and each of those may be have been last loaded on a different cpu. Our solution is to hold, in addition to vcpus_on_cpu, a second linked list saved_vmcss_on_cpu, which holds the current list of "saved" VMCSs, i.e., VMCSs which are loaded on this CPU but are not the vmx->vmcs of any of the vcpus. These saved VMCSs include L1's VMCS while L2 is running (saved_vmcs01), and L2 VMCSs not currently used - because L1 is running or because the vmcs02_pool contains more than one entry. When we will switch between L1's and L2's VMCSs, they need to be moved between vcpus_on_cpu and saved_vmcs_on_cpu lists and vice versa. A new function, nested_maintain_per_cpu_lists(), takes care of that. Signed-off-by: Nadav Har'El --- arch/x86/kvm/vmx.c | 67 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 67 insertions(+) --- .before/arch/x86/kvm/vmx.c 2011-05-16 22:36:47.000000000 +0300 +++ .after/arch/x86/kvm/vmx.c 2011-05-16 22:36:47.000000000 +0300 @@ -181,6 +181,7 @@ struct saved_vmcs { struct vmcs *vmcs; int cpu; int launched; + struct list_head local_saved_vmcss_link; /* see saved_vmcss_on_cpu */ }; /* Used to remember the last vmcs02 used for some recently used vmcs12s */ @@ -315,7 +316,20 @@ static int vmx_set_tss_addr(struct kvm * static DEFINE_PER_CPU(struct vmcs *, vmxarea); static DEFINE_PER_CPU(struct vmcs *, current_vmcs); +/* + * We maintain a per-CPU linked-list vcpus_on_cpu, holding for each CPU a list + * of vcpus whose VMCS are loaded on that CPU. This is needed when a CPU is + * brought down, and we need to VMCLEAR all VMCSs loaded on it. + * + * With nested VMX, we have additional VMCSs which are not the current + * vmx->vmcs of any vcpu, but may also be loaded on some CPU: While L2 is + * running, L1's VMCS is loaded but not the VMCS of any vcpu; While L1 is + * running, a previously used L2 VMCS might still be around and loaded on some + * CPU, somes even more than one such L2 VMCSs is kept (see VMCS02_POOL_SIZE). + * The list of these additional VMCSs is kept on cpu saved_vmcss_on_cpu. + */ static DEFINE_PER_CPU(struct list_head, vcpus_on_cpu); +static DEFINE_PER_CPU(struct list_head, saved_vmcss_on_cpu); static DEFINE_PER_CPU(struct desc_ptr, host_gdt); static unsigned long *vmx_io_bitmap_a; @@ -1818,6 +1832,7 @@ static int hardware_enable(void *garbage return -EBUSY; INIT_LIST_HEAD(&per_cpu(vcpus_on_cpu, cpu)); + INIT_LIST_HEAD(&per_cpu(saved_vmcss_on_cpu, cpu)); rdmsrl(MSR_IA32_FEATURE_CONTROL, old); test_bits = FEATURE_CONTROL_LOCKED; @@ -1860,10 +1875,13 @@ static void kvm_cpu_vmxoff(void) asm volatile (__ex(ASM_VMX_VMXOFF) : : : "cc"); } +static void vmclear_local_saved_vmcss(void); + static void hardware_disable(void *garbage) { if (vmm_exclusive) { vmclear_local_vcpus(); + vmclear_local_saved_vmcss(); kvm_cpu_vmxoff(); } write_cr4(read_cr4() & ~X86_CR4_VMXE); @@ -4248,6 +4266,8 @@ static void __nested_free_saved_vmcs(voi vmcs_clear(saved_vmcs->vmcs); if (per_cpu(current_vmcs, saved_vmcs->cpu) == saved_vmcs->vmcs) per_cpu(current_vmcs, saved_vmcs->cpu) = NULL; + list_del(&saved_vmcs->local_saved_vmcss_link); + saved_vmcs->cpu = -1; } /* @@ -4265,6 +4285,21 @@ static void nested_free_saved_vmcs(struc free_vmcs(saved_vmcs->vmcs); } +/* + * VMCLEAR all the currently unused (not vmx->vmcs on any vcpu) saved_vmcss + * which were loaded on the current CPU. See also vmclear_load_vcpus(), which + * does the same for VMCS currently used in vcpus. + */ +static void vmclear_local_saved_vmcss(void) +{ + int cpu = raw_smp_processor_id(); + struct saved_vmcs *v, *n; + + list_for_each_entry_safe(v, n, &per_cpu(saved_vmcss_on_cpu, cpu), + local_saved_vmcss_link) + __nested_free_saved_vmcs(v); +} + /* Free and remove from pool a vmcs02 saved for a vmcs12 (if there is one) */ static void nested_free_vmcs02(struct vcpu_vmx *vmx, gpa_t vmptr) { @@ -5143,6 +5178,38 @@ static void vmx_set_supported_cpuid(u32 { } +/* + * Maintain the vcpus_on_cpu and saved_vmcss_on_cpu lists of vcpus and + * inactive saved_vmcss on nested entry (L1->L2) or nested exit (L2->L1). + * + * nested_maintain_per_cpu_lists should be called after the VMCS was switched + * to the new one, with parameters giving both the new on (after the entry + * or exit) and the old one, in that order. + */ +static void nested_maintain_per_cpu_lists(struct vcpu_vmx *vmx, + struct saved_vmcs *new_vmcs, + struct saved_vmcs *old_vmcs) +{ + /* + * When a vcpus's old vmcs is saved, we need to drop it from + * vcpus_on_cpu and put it on saved_vmcss_on_cpu. + */ + if (old_vmcs->cpu != -1) { + list_del(&vmx->local_vcpus_link); + list_add(&old_vmcs->local_saved_vmcss_link, + &per_cpu(saved_vmcss_on_cpu, old_vmcs->cpu)); + } + /* + * When a saved vmcs becomes a vcpu's new vmcs, we need to drop it + * from saved_vmcss_on_cpu and put it on vcpus_on_cpu. + */ + if (new_vmcs->cpu != -1) { + list_del(&new_vmcs->local_saved_vmcss_link); + list_add(&vmx->local_vcpus_link, + &per_cpu(vcpus_on_cpu, new_vmcs->cpu)); + } +} + static int vmx_check_intercept(struct kvm_vcpu *vcpu, struct x86_instruction_info *info, enum x86_intercept_stage stage)