Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753779AbaKAWxx (ORCPT ); Sat, 1 Nov 2014 18:53:53 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:60096 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751495AbaKAWj2 (ORCPT ); Sat, 1 Nov 2014 18:39:28 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Paolo Bonzini" , "Petr Matousek" , "Andy Lutomirski" , "Linus Torvalds" , stable@vger.kernel.org, "Gleb Natapov" Date: Sat, 01 Nov 2014 22:28:03 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 097/102] x86,kvm,vmx: Preserve CR4 across VM entry In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.64-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit d974baa398f34393db76be45f7d4d04fbdbb4a0a upstream. CR4 isn't constant; at least the TSD and PCE bits can vary. TBH, treating CR0 and CR3 as constant scares me a bit, too, but it looks like it's correct. This adds a branch and a read from cr4 to each vm entry. Because it is extremely likely that consecutive entries into the same vcpu will have the same host cr4 value, this fixes up the vmcs instead of restoring cr4 after the fact. A subsequent patch will add a kernel-wide cr4 shadow, reducing the overhead in the common case to just two memory reads and a branch. Signed-off-by: Andy Lutomirski Acked-by: Paolo Bonzini Cc: stable@vger.kernel.org Cc: Petr Matousek Cc: Gleb Natapov Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: - Adjust context - Add struct vcpu_vmx *vmx parameter to vmx_set_constant_host_state(), done upstream in commit a547c6db4d2f ("KVM: VMX: Enable acknowledge interupt on vmexit")] Signed-off-by: Ben Hutchings --- arch/x86/kvm/vmx.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -390,6 +390,7 @@ struct vcpu_vmx { u16 fs_sel, gs_sel, ldt_sel; int gs_ldt_reload_needed; int fs_reload_needed; + unsigned long vmcs_host_cr4; /* May not match real cr4 */ } host_state; struct { int vm86_active; @@ -3631,16 +3632,21 @@ static void vmx_disable_intercept_for_ms * Note that host-state that does change is set elsewhere. E.g., host-state * that is set differently for each CPU is set in vmx_vcpu_load(), not here. */ -static void vmx_set_constant_host_state(void) +static void vmx_set_constant_host_state(struct vcpu_vmx *vmx) { u32 low32, high32; unsigned long tmpl; struct desc_ptr dt; + unsigned long cr4; vmcs_writel(HOST_CR0, read_cr0() | X86_CR0_TS); /* 22.2.3 */ - vmcs_writel(HOST_CR4, read_cr4()); /* 22.2.3, 22.2.5 */ vmcs_writel(HOST_CR3, read_cr3()); /* 22.2.3 FIXME: shadow tables */ + /* Save the most likely value for this task's CR4 in the VMCS. */ + cr4 = read_cr4(); + vmcs_writel(HOST_CR4, cr4); /* 22.2.3, 22.2.5 */ + vmx->host_state.vmcs_host_cr4 = cr4; + vmcs_write16(HOST_CS_SELECTOR, __KERNEL_CS); /* 22.2.4 */ vmcs_write16(HOST_DS_SELECTOR, __KERNEL_DS); /* 22.2.4 */ vmcs_write16(HOST_ES_SELECTOR, __KERNEL_DS); /* 22.2.4 */ @@ -3762,7 +3768,7 @@ static int vmx_vcpu_setup(struct vcpu_vm vmcs_write16(HOST_FS_SELECTOR, 0); /* 22.2.4 */ vmcs_write16(HOST_GS_SELECTOR, 0); /* 22.2.4 */ - vmx_set_constant_host_state(); + vmx_set_constant_host_state(vmx); #ifdef CONFIG_X86_64 rdmsrl(MSR_FS_BASE, a); vmcs_writel(HOST_FS_BASE, a); /* 22.2.4 */ @@ -6172,6 +6178,7 @@ static void atomic_switch_perf_msrs(stru static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); + unsigned long cr4; if (is_guest_mode(vcpu) && !vmx->nested.nested_run_pending) { struct vmcs12 *vmcs12 = get_vmcs12(vcpu); @@ -6202,6 +6209,12 @@ static void __noclone vmx_vcpu_run(struc if (test_bit(VCPU_REGS_RIP, (unsigned long *)&vcpu->arch.regs_dirty)) vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]); + cr4 = read_cr4(); + if (unlikely(cr4 != vmx->host_state.vmcs_host_cr4)) { + vmcs_writel(HOST_CR4, cr4); + vmx->host_state.vmcs_host_cr4 = cr4; + } + /* When single-stepping over STI and MOV SS, we must clear the * corresponding interruptibility bits in the guest state. Otherwise * vmentry fails as it then expects bit 14 (BS) in pending debug @@ -6666,7 +6679,7 @@ static void prepare_vmcs02(struct kvm_vc * Other fields are different per CPU, and will be set later when * vmx_vcpu_load() is called, and when vmx_save_host_state() is called. */ - vmx_set_constant_host_state(); + vmx_set_constant_host_state(vmx); /* * HOST_RSP is normally set correctly in vmx_vcpu_run() just before -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/