x86,kvm,vmx: Preserve CR4 across VM entry

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 <luto@amacapital.net>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Cc: Petr Matousek <pmatouse@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
static int __init vmx_init(void)
{
	int r, i, msr;

	rdmsrl_safe(MSR_EFER, &host_efer);

	for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i)
		kvm_define_shared_msr(i, vmx_msr_index[i]);

	vmx_io_bitmap_a = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_io_bitmap_a)
		return -ENOMEM;

	r = -ENOMEM;

	vmx_io_bitmap_b = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_io_bitmap_b)
		goto out;

	vmx_msr_bitmap_legacy = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_msr_bitmap_legacy)
		goto out1;

	vmx_msr_bitmap_legacy_x2apic =
				(unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_msr_bitmap_legacy_x2apic)
		goto out2;

	vmx_msr_bitmap_longmode = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_msr_bitmap_longmode)
		goto out3;

	vmx_msr_bitmap_longmode_x2apic =
				(unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_msr_bitmap_longmode_x2apic)
		goto out4;
	vmx_vmread_bitmap = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_vmread_bitmap)
		goto out5;

	vmx_vmwrite_bitmap = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_vmwrite_bitmap)
		goto out6;

	memset(vmx_vmread_bitmap, 0xff, PAGE_SIZE);
	memset(vmx_vmwrite_bitmap, 0xff, PAGE_SIZE);

	/*
	 * Allow direct access to the PC debug port (it is often used for I/O
	 * delays, but the vmexits simply slow things down).
	 */
	memset(vmx_io_bitmap_a, 0xff, PAGE_SIZE);
	clear_bit(0x80, vmx_io_bitmap_a);

	memset(vmx_io_bitmap_b, 0xff, PAGE_SIZE);

	memset(vmx_msr_bitmap_legacy, 0xff, PAGE_SIZE);
	memset(vmx_msr_bitmap_longmode, 0xff, PAGE_SIZE);

	set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */

	r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
		     __alignof__(struct vcpu_vmx), THIS_MODULE);
	if (r)
		goto out7;

#ifdef CONFIG_KEXEC
	rcu_assign_pointer(crash_vmclear_loaded_vmcss,
			   crash_vmclear_local_loaded_vmcss);
#endif

	vmx_disable_intercept_for_msr(MSR_FS_BASE, false);
	vmx_disable_intercept_for_msr(MSR_GS_BASE, false);
	vmx_disable_intercept_for_msr(MSR_KERNEL_GS_BASE, true);
	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_CS, false);
	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_ESP, false);
	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false);
	vmx_disable_intercept_for_msr(MSR_IA32_BNDCFGS, true);

	memcpy(vmx_msr_bitmap_legacy_x2apic,
			vmx_msr_bitmap_legacy, PAGE_SIZE);
	memcpy(vmx_msr_bitmap_longmode_x2apic,
			vmx_msr_bitmap_longmode, PAGE_SIZE);

	if (enable_apicv) {
		for (msr = 0x800; msr <= 0x8ff; msr++)
			vmx_disable_intercept_msr_read_x2apic(msr);

		/* According SDM, in x2apic mode, the whole id reg is used.
		 * But in KVM, it only use the highest eight bits. Need to
		 * intercept it */
		vmx_enable_intercept_msr_read_x2apic(0x802);
		/* TMCCT */
		vmx_enable_intercept_msr_read_x2apic(0x839);
		/* TPR */
		vmx_disable_intercept_msr_write_x2apic(0x808);
		/* EOI */
		vmx_disable_intercept_msr_write_x2apic(0x80b);
		/* SELF-IPI */
		vmx_disable_intercept_msr_write_x2apic(0x83f);
	}

	if (enable_ept) {
		kvm_mmu_set_mask_ptes(0ull,
			(enable_ept_ad_bits) ? VMX_EPT_ACCESS_BIT : 0ull,
			(enable_ept_ad_bits) ? VMX_EPT_DIRTY_BIT : 0ull,
			0ull, VMX_EPT_EXECUTABLE_MASK);
		ept_set_mmio_spte_mask();
		kvm_enable_tdp();
	} else
		kvm_disable_tdp();

	update_ple_window_actual_max();

	return 0;

out7:
	free_page((unsigned long)vmx_vmwrite_bitmap);
out6:
	free_page((unsigned long)vmx_vmread_bitmap);
out5:
	free_page((unsigned long)vmx_msr_bitmap_longmode_x2apic);
out4:
	free_page((unsigned long)vmx_msr_bitmap_longmode);
out3:
	free_page((unsigned long)vmx_msr_bitmap_legacy_x2apic);
out2:
	free_page((unsigned long)vmx_msr_bitmap_legacy);
out1:
	free_page((unsigned long)vmx_io_bitmap_b);
out:
	free_page((unsigned long)vmx_io_bitmap_a);
	return r;
}

static int __init vmx_init(void)
{
	int r, i, msr;

	rdmsrl_safe(MSR_EFER, &host_efer);

	for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i)
		kvm_define_shared_msr(i, vmx_msr_index[i]);

	vmx_io_bitmap_a = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_io_bitmap_a)
		return -ENOMEM;

	r = -ENOMEM;

	vmx_io_bitmap_b = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_io_bitmap_b)
		goto out;

	vmx_msr_bitmap_legacy = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_msr_bitmap_legacy)
		goto out1;

	vmx_msr_bitmap_legacy_x2apic =
				(unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_msr_bitmap_legacy_x2apic)
		goto out2;

	vmx_msr_bitmap_longmode = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_msr_bitmap_longmode)
		goto out3;

	vmx_msr_bitmap_longmode_x2apic =
				(unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_msr_bitmap_longmode_x2apic)
		goto out4;
	vmx_vmread_bitmap = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_vmread_bitmap)
		goto out5;

	vmx_vmwrite_bitmap = (unsigned long *)__get_free_page(GFP_KERNEL);
	if (!vmx_vmwrite_bitmap)
		goto out6;

	memset(vmx_vmread_bitmap, 0xff, PAGE_SIZE);
	memset(vmx_vmwrite_bitmap, 0xff, PAGE_SIZE);

	/*
	 * Allow direct access to the PC debug port (it is often used for I/O
	 * delays, but the vmexits simply slow things down).
	 */
	memset(vmx_io_bitmap_a, 0xff, PAGE_SIZE);
	clear_bit(0x80, vmx_io_bitmap_a);

	memset(vmx_io_bitmap_b, 0xff, PAGE_SIZE);

	memset(vmx_msr_bitmap_legacy, 0xff, PAGE_SIZE);
	memset(vmx_msr_bitmap_longmode, 0xff, PAGE_SIZE);

	set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */

	r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
		     __alignof__(struct vcpu_vmx), THIS_MODULE);
	if (r)
		goto out7;

#ifdef CONFIG_KEXEC
	rcu_assign_pointer(crash_vmclear_loaded_vmcss,
			   crash_vmclear_local_loaded_vmcss);
#endif

	vmx_disable_intercept_for_msr(MSR_FS_BASE, false);
	vmx_disable_intercept_for_msr(MSR_GS_BASE, false);
	vmx_disable_intercept_for_msr(MSR_KERNEL_GS_BASE, true);
	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_CS, false);
	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_ESP, false);
	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false);
	vmx_disable_intercept_for_msr(MSR_IA32_BNDCFGS, true);

	memcpy(vmx_msr_bitmap_legacy_x2apic,
			vmx_msr_bitmap_legacy, PAGE_SIZE);
	memcpy(vmx_msr_bitmap_longmode_x2apic,
			vmx_msr_bitmap_longmode, PAGE_SIZE);

	if (enable_apicv) {
		for (msr = 0x800; msr <= 0x8ff; msr++)
			vmx_disable_intercept_msr_read_x2apic(msr);

		/* According SDM, in x2apic mode, the whole id reg is used.
		 * But in KVM, it only use the highest eight bits. Need to
		 * intercept it */
		vmx_enable_intercept_msr_read_x2apic(0x802);
		/* TMCCT */
		vmx_enable_intercept_msr_read_x2apic(0x839);
		/* TPR */
		vmx_disable_intercept_msr_write_x2apic(0x808);
		/* EOI */
		vmx_disable_intercept_msr_write_x2apic(0x80b);
		/* SELF-IPI */
		vmx_disable_intercept_msr_write_x2apic(0x83f);
	}

	if (enable_ept) {
		kvm_mmu_set_mask_ptes(0ull,
			(enable_ept_ad_bits) ? VMX_EPT_ACCESS_BIT : 0ull,
			(enable_ept_ad_bits) ? VMX_EPT_DIRTY_BIT : 0ull,
			0ull, VMX_EPT_EXECUTABLE_MASK);
		ept_set_mmio_spte_mask();
		kvm_enable_tdp();
	} else
		kvm_disable_tdp();

	update_ple_window_actual_max();

	return 0;

out7:
	free_page((unsigned long)vmx_vmwrite_bitmap);
out6:
	free_page((unsigned long)vmx_vmread_bitmap);
out5:
	free_page((unsigned long)vmx_msr_bitmap_longmode_x2apic);
out4:
	free_page((unsigned long)vmx_msr_bitmap_longmode);
out3:
	free_page((unsigned long)vmx_msr_bitmap_legacy_x2apic);
out2:
	free_page((unsigned long)vmx_msr_bitmap_legacy);
out1:
	free_page((unsigned long)vmx_io_bitmap_b);
out:
	free_page((unsigned long)vmx_io_bitmap_a);
	return r;
}
