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Commit 6d9658df authored by Ingo Molnar's avatar Ingo Molnar Committed by Avi Kivity
Browse files

KVM: always reload segment selectors 



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: default avatarIngo Molnar <mingo@elte.hu>
parent 6af11b9e

drivers/kvm/vmx.c

+21 −16
Original line number Diff line number Diff line
@@ -1888,6 +1888,27 @@ 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);
@@ -1905,22 +1926,6 @@ 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:

		 */