Commit bb58b90b authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: Introduce KVM_SET_USER_MEMORY_REGION2 



Introduce a "version 2" of KVM_SET_USER_MEMORY_REGION so that additional
information can be supplied without setting userspace up to fail.  The
padding in the new kvm_userspace_memory_region2 structure will be used to
pass a file descriptor in addition to the userspace_addr, i.e. allow
userspace to point at a file descriptor and map memory into a guest that
is NOT mapped into host userspace.

Alternatively, KVM could simply add "struct kvm_userspace_memory_region2"
without a new ioctl(), but as Paolo pointed out, adding a new ioctl()
makes detection of bad flags a bit more robust, e.g. if the new fd field
is guarded only by a flag and not a new ioctl(), then a userspace bug
(setting a "bad" flag) would generate out-of-bounds access instead of an
-EINVAL error.

Cc: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarFuad Tabba <tabba@google.com>
Tested-by: default avatarFuad Tabba <tabba@google.com>
Message-Id: <20231027182217.3615211-9-seanjc@google.com>
Acked-by: default avatarKai Huang <kai.huang@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent f128cf8c

Documentation/virt/kvm/api.rst

+22 −0
Original line number Diff line number Diff line
@@ -6192,6 +6192,28 @@ to know what fields can be changed for the system register described by 
``op0, op1, crn, crm, op2``. KVM rejects ID register values that describe a

superset of the features supported by the system.



4.140 KVM_SET_USER_MEMORY_REGION2

---------------------------------



:Capability: KVM_CAP_USER_MEMORY2

:Architectures: all

:Type: vm ioctl

:Parameters: struct kvm_userspace_memory_region2 (in)

:Returns: 0 on success, -1 on error



::



  struct kvm_userspace_memory_region2 {

	__u32 slot;

	__u32 flags;

	__u64 guest_phys_addr;

	__u64 memory_size; /* bytes */

	__u64 userspace_addr; /* start of the userspace allocated memory */

	__u64 pad[16];

  };



See KVM_SET_USER_MEMORY_REGION.



5. The kvm_run structure

========================

arch/x86/kvm/x86.c

+1 −1
Original line number Diff line number Diff line
@@ -12576,7 +12576,7 @@ void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, 
	}



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

		struct kvm_userspace_memory_region m;

		struct kvm_userspace_memory_region2 m;



		m.slot = id | (i << 16);

		m.flags = 0;

include/linux/kvm_host.h

+2 −2
Original line number Diff line number Diff line
@@ -1146,9 +1146,9 @@ enum kvm_mr_change { 
};



int kvm_set_memory_region(struct kvm *kvm,

			  const struct kvm_userspace_memory_region *mem);

			  const struct kvm_userspace_memory_region2 *mem);

int __kvm_set_memory_region(struct kvm *kvm,

			    const struct kvm_userspace_memory_region *mem);

			    const struct kvm_userspace_memory_region2 *mem);

void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);

void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen);

int kvm_arch_prepare_memory_region(struct kvm *kvm,

include/uapi/linux/kvm.h

+13 −0
Original line number Diff line number Diff line
@@ -95,6 +95,16 @@ struct kvm_userspace_memory_region { 
	__u64 userspace_addr; /* start of the userspace allocated memory */

};



/* for KVM_SET_USER_MEMORY_REGION2 */

struct kvm_userspace_memory_region2 {

	__u32 slot;

	__u32 flags;

	__u64 guest_phys_addr;

	__u64 memory_size;

	__u64 userspace_addr;

	__u64 pad[16];

};



/*

 * The bit 0 ~ bit 15 of kvm_userspace_memory_region::flags are visible for

 * userspace, other bits are reserved for kvm internal use which are defined
@@ -1201,6 +1211,7 @@ struct kvm_ppc_resize_hpt { 
#define KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE 228

#define KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES 229

#define KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES 230

#define KVM_CAP_USER_MEMORY2 231



#ifdef KVM_CAP_IRQ_ROUTING
@@ -1483,6 +1494,8 @@ struct kvm_vfio_spapr_tce { 
					struct kvm_userspace_memory_region)

#define KVM_SET_TSS_ADDR          _IO(KVMIO,   0x47)

#define KVM_SET_IDENTITY_MAP_ADDR _IOW(KVMIO,  0x48, __u64)

#define KVM_SET_USER_MEMORY_REGION2 _IOW(KVMIO, 0x49, \

					 struct kvm_userspace_memory_region2)



/* enable ucontrol for s390 */

struct kvm_s390_ucas_mapping {

virt/kvm/kvm_main.c

+49 −8
Original line number Diff line number Diff line
@@ -1580,7 +1580,15 @@ static void kvm_replace_memslot(struct kvm *kvm, 
	}

}



static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem)

/*

 * Flags that do not access any of the extra space of struct

 * kvm_userspace_memory_region2.  KVM_SET_USER_MEMORY_REGION_V1_FLAGS

 * only allows these.

 */

#define KVM_SET_USER_MEMORY_REGION_V1_FLAGS \

	(KVM_MEM_LOG_DIRTY_PAGES | KVM_MEM_READONLY)



static int check_memory_region_flags(const struct kvm_userspace_memory_region2 *mem)

{

	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
@@ -1982,7 +1990,7 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id, 
 * Must be called holding kvm->slots_lock for write.

 */

int __kvm_set_memory_region(struct kvm *kvm,

			    const struct kvm_userspace_memory_region *mem)

			    const struct kvm_userspace_memory_region2 *mem)

{

	struct kvm_memory_slot *old, *new;

	struct kvm_memslots *slots;
@@ -2086,7 +2094,7 @@ int __kvm_set_memory_region(struct kvm *kvm, 
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);



int kvm_set_memory_region(struct kvm *kvm,

			  const struct kvm_userspace_memory_region *mem)

			  const struct kvm_userspace_memory_region2 *mem)

{

	int r;
@@ -2098,7 +2106,7 @@ int kvm_set_memory_region(struct kvm *kvm, 
EXPORT_SYMBOL_GPL(kvm_set_memory_region);



static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,

					  struct kvm_userspace_memory_region *mem)

					  struct kvm_userspace_memory_region2 *mem)

{

	if ((u16)mem->slot >= KVM_USER_MEM_SLOTS)

		return -EINVAL;
@@ -4568,6 +4576,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) 
{

	switch (arg) {

	case KVM_CAP_USER_MEMORY:

	case KVM_CAP_USER_MEMORY2:

	case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:

	case KVM_CAP_JOIN_MEMORY_REGIONS_WORKS:

	case KVM_CAP_INTERNAL_ERROR_DATA:
@@ -4823,6 +4832,14 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm) 
	return fd;

}



#define SANITY_CHECK_MEM_REGION_FIELD(field)					\

do {										\

	BUILD_BUG_ON(offsetof(struct kvm_userspace_memory_region, field) !=		\

		     offsetof(struct kvm_userspace_memory_region2, field));	\

	BUILD_BUG_ON(sizeof_field(struct kvm_userspace_memory_region, field) !=		\

		     sizeof_field(struct kvm_userspace_memory_region2, field));	\

} while (0)



static long kvm_vm_ioctl(struct file *filp,

			   unsigned int ioctl, unsigned long arg)

{
@@ -4845,15 +4862,39 @@ static long kvm_vm_ioctl(struct file *filp, 
		r = kvm_vm_ioctl_enable_cap_generic(kvm, &cap);

		break;

	}

	case KVM_SET_USER_MEMORY_REGION2:

	case KVM_SET_USER_MEMORY_REGION: {

		struct kvm_userspace_memory_region kvm_userspace_mem;

		struct kvm_userspace_memory_region2 mem;

		unsigned long size;



		if (ioctl == KVM_SET_USER_MEMORY_REGION) {

			/*

			 * Fields beyond struct kvm_userspace_memory_region shouldn't be

			 * accessed, but avoid leaking kernel memory in case of a bug.

			 */

			memset(&mem, 0, sizeof(mem));

			size = sizeof(struct kvm_userspace_memory_region);

		} else {

			size = sizeof(struct kvm_userspace_memory_region2);

		}



		/* Ensure the common parts of the two structs are identical. */

		SANITY_CHECK_MEM_REGION_FIELD(slot);

		SANITY_CHECK_MEM_REGION_FIELD(flags);

		SANITY_CHECK_MEM_REGION_FIELD(guest_phys_addr);

		SANITY_CHECK_MEM_REGION_FIELD(memory_size);

		SANITY_CHECK_MEM_REGION_FIELD(userspace_addr);



		r = -EFAULT;

		if (copy_from_user(&kvm_userspace_mem, argp,

						sizeof(kvm_userspace_mem)))

		if (copy_from_user(&mem, argp, size))

			goto out;



		r = -EINVAL;

		if (ioctl == KVM_SET_USER_MEMORY_REGION &&

		    (mem.flags & ~KVM_SET_USER_MEMORY_REGION_V1_FLAGS))

			goto out;



		r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem);

		r = kvm_vm_ioctl_set_memory_region(kvm, &mem);

		break;

	}

	case KVM_GET_DIRTY_LOG: {