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Commit fe2b201b authored by Bandan Das's avatar Bandan Das Committed by Paolo Bonzini
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KVM: x86: Check for host supported fields in shadow vmcs 



We track shadow vmcs fields through two static lists,
one for read only and another for r/w fields. However, with
addition of new vmcs fields, not all fields may be supported on
all hosts. If so, copy_vmcs12_to_shadow() trying to vmwrite on
unsupported hosts will result in a vmwrite error. For example, commit
36be0b9d introduced GUEST_BNDCFGS, which is not supported
by all processors. Filter out host unsupported fields before
letting guests use shadow vmcs

Signed-off-by: default avatarBandan Das <bsd@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent e8e249d7

arch/x86/kvm/vmx.c

+41 −12
Original line number Diff line number Diff line
@@ -503,7 +503,7 @@ static inline struct vcpu_vmx *to_vmx(struct kvm_vcpu *vcpu) 
				[number##_HIGH] = VMCS12_OFFSET(name)+4





static const unsigned long shadow_read_only_fields[] = {

static unsigned long shadow_read_only_fields[] = {

	/*

	 * We do NOT shadow fields that are modified when L0

	 * traps and emulates any vmx instruction (e.g. VMPTRLD,
@@ -526,10 +526,10 @@ static const unsigned long shadow_read_only_fields[] = { 
	GUEST_LINEAR_ADDRESS,

	GUEST_PHYSICAL_ADDRESS

};

static const int max_shadow_read_only_fields =

static int max_shadow_read_only_fields =

	ARRAY_SIZE(shadow_read_only_fields);



static const unsigned long shadow_read_write_fields[] = {

static unsigned long shadow_read_write_fields[] = {

	GUEST_RIP,

	GUEST_RSP,

	GUEST_CR0,
@@ -558,7 +558,7 @@ static const unsigned long shadow_read_write_fields[] = { 
	HOST_FS_SELECTOR,

	HOST_GS_SELECTOR

};

static const int max_shadow_read_write_fields =

static int max_shadow_read_write_fields =

	ARRAY_SIZE(shadow_read_write_fields);



static const unsigned short vmcs_field_to_offset_table[] = {
@@ -3009,6 +3009,41 @@ static void free_kvm_area(void) 
	}

}



static void init_vmcs_shadow_fields(void)

{

	int i, j;



	/* No checks for read only fields yet */



	for (i = j = 0; i < max_shadow_read_write_fields; i++) {

		switch (shadow_read_write_fields[i]) {

		case GUEST_BNDCFGS:

			if (!vmx_mpx_supported())

				continue;

			break;

		default:

			break;

		}



		if (j < i)

			shadow_read_write_fields[j] =

				shadow_read_write_fields[i];

		j++;

	}

	max_shadow_read_write_fields = j;



	/* shadowed fields guest access without vmexit */

	for (i = 0; i < max_shadow_read_write_fields; i++) {

		clear_bit(shadow_read_write_fields[i],

			  vmx_vmwrite_bitmap);

		clear_bit(shadow_read_write_fields[i],

			  vmx_vmread_bitmap);

	}

	for (i = 0; i < max_shadow_read_only_fields; i++)

		clear_bit(shadow_read_only_fields[i],

			  vmx_vmread_bitmap);

}



static __init int alloc_kvm_area(void)

{

	int cpu;
@@ -3039,6 +3074,8 @@ static __init int hardware_setup(void) 
		enable_vpid = 0;

	if (!cpu_has_vmx_shadow_vmcs())

		enable_shadow_vmcs = 0;

	if (enable_shadow_vmcs)

		init_vmcs_shadow_fields();



	if (!cpu_has_vmx_ept() ||

	    !cpu_has_vmx_ept_4levels()) {
@@ -8803,14 +8840,6 @@ static int __init vmx_init(void) 


	memset(vmx_vmread_bitmap, 0xff, PAGE_SIZE);

	memset(vmx_vmwrite_bitmap, 0xff, PAGE_SIZE);

	/* shadowed read/write fields */

	for (i = 0; i < max_shadow_read_write_fields; i++) {

		clear_bit(shadow_read_write_fields[i], vmx_vmwrite_bitmap);

		clear_bit(shadow_read_write_fields[i], vmx_vmread_bitmap);

	}

	/* shadowed read only fields */

	for (i = 0; i < max_shadow_read_only_fields; i++)

		clear_bit(shadow_read_only_fields[i], vmx_vmread_bitmap);



	/*

	 * Allow direct access to the PC debug port (it is often used for I/O