Re: [PATCH 9/24] Implement VMCLEAR

["Nadav Har'El" <nyh@math.technion.ac.il>]

On Thu, Aug 05, 2010, Avi Kivity wrote about "Re: [PATCH 9/24] Implement VMCLEAR":
> >Do you think it's a good idea to kill
> >the guest immediately, in anticipation of a crash that will most likely 
> >come
> >later?
> 
> At this stage, the problem is likely to be in the nvmx implementation.  
> So it's best to report the problem as early as possible.

Ok, here is the new version of this patch, implementing this case by doing a
triple fault (I hope this is what you meant by KVM_REQ_SHUTDOWN), and also
with other fixes as suggested by you, Gleb and Eddie.

----
Subject: [PATCH 10/26] nVMX: Implement VMCLEAR

This patch implements the VMCLEAR instruction.

Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
---
 arch/x86/kvm/vmx.c |   62 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

--- .before/arch/x86/kvm/vmx.c	2010-08-05 15:22:27.000000000 +0300
+++ .after/arch/x86/kvm/vmx.c	2010-08-05 15:22:27.000000000 +0300
@@ -144,6 +144,8 @@ struct __packed vmcs12 {
 	 */
 	u32 revision_id;
 	u32 abort;
+
+	bool launch_state; /* set to 0 by VMCLEAR, to 1 by VMLAUNCH */
 };
 
 /*
@@ -3828,6 +3830,64 @@ static void nested_vmx_failValid(struct 
 	get_vmcs12_fields(vcpu)->vm_instruction_error = vm_instruction_error;
 }
 
+/* Emulate the VMCLEAR instruction */
+static int handle_vmclear(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	gva_t gva;
+	gpa_t vmcs12_addr;
+	struct vmcs12 *vmcs12;
+	struct page *page;
+
+	if (!nested_vmx_check_permission(vcpu))
+		return 1;
+
+	if (get_vmx_mem_address(vcpu, vmcs_readl(EXIT_QUALIFICATION),
+			vmcs_read32(VMX_INSTRUCTION_INFO), &gva))
+		return 1;
+
+	if (kvm_read_guest_virt(gva, &vmcs12_addr, sizeof(vmcs12_addr),
+				vcpu, NULL)) {
+		kvm_queue_exception(vcpu, PF_VECTOR);
+		return 1;
+	}
+
+	if (!IS_ALIGNED(vmcs12_addr, PAGE_SIZE)) {
+		nested_vmx_failValid(vcpu, VMXERR_VMCLEAR_INVALID_ADDRESS);
+		skip_emulated_instruction(vcpu);
+		return 1;
+	}
+
+	if (vmcs12_addr == vmx->nested.current_vmptr){
+		kunmap(vmx->nested.current_vmcs12_page);
+		nested_release_page(vmx->nested.current_vmcs12_page);
+		vmx->nested.current_vmptr = -1ull;
+	}
+
+	page = nested_get_page(vcpu, vmcs12_addr);
+	if(page == NULL){
+		/*
+		 * For accurate processor emulation, VMCLEAR beyond available
+		 * physical memory should do nothing at all. However, it is
+		 * possible that a nested vmx bug, not a guest hypervisor bug,
+		 * resulted in this case, so let's shut down before doing any
+		 * more damage:
+		 */
+		set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
+		return 1;
+	}
+	vmcs12 = kmap(page);
+	vmcs12->launch_state = 0;
+	kunmap(page);
+	nested_release_page(page);
+
+	nested_free_vmcs(vcpu, vmcs12_addr);
+
+	skip_emulated_instruction(vcpu);
+	nested_vmx_succeed(vcpu);
+	return 1;
+}
+
 static int handle_invlpg(struct kvm_vcpu *vcpu)
 {
 	unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
@@ -4110,7 +4170,7 @@ static int (*kvm_vmx_exit_handlers[])(st
 	[EXIT_REASON_HLT]                     = handle_halt,
 	[EXIT_REASON_INVLPG]		      = handle_invlpg,
 	[EXIT_REASON_VMCALL]                  = handle_vmcall,
-	[EXIT_REASON_VMCLEAR]	              = handle_vmx_insn,
+	[EXIT_REASON_VMCLEAR]	              = handle_vmclear,
 	[EXIT_REASON_VMLAUNCH]                = handle_vmx_insn,
 	[EXIT_REASON_VMPTRLD]                 = handle_vmx_insn,
 	[EXIT_REASON_VMPTRST]                 = handle_vmx_insn,

-- 
Nadav Har'El                        |        Thursday, Aug  5 2010, 25 Av 5770
nyh@math.technion.ac.il             |-----------------------------------------
Phone +972-523-790466, ICQ 13349191 |A fine is a tax for doing wrong. A tax is
http://nadav.harel.org.il           |a fine for doing well.