@@ -157,7 +157,8 @@ static inline void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd) {
static inline void fpu_sync_guest_vmexit_xfd_state(void) { }
#endif
-extern void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf, unsigned int size, u32 pkru);
+extern void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf,
+ unsigned int size, u64 xfeatures, u32 pkru);
extern int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, u64 xcr0, u32 *vpkru);
static inline void fpstate_set_confidential(struct fpu_guest *gfpu)
@@ -369,14 +369,15 @@ int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)
EXPORT_SYMBOL_GPL(fpu_swap_kvm_fpstate);
void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf,
- unsigned int size, u32 pkru)
+ unsigned int size, u64 xfeatures, u32 pkru)
{
struct fpstate *kstate = gfpu->fpstate;
union fpregs_state *ustate = buf;
struct membuf mb = { .p = buf, .left = size };
if (cpu_feature_enabled(X86_FEATURE_XSAVE)) {
- __copy_xstate_to_uabi_buf(mb, kstate, pkru, XSTATE_COPY_XSAVE);
+ __copy_xstate_to_uabi_buf(mb, kstate, xfeatures, pkru,
+ XSTATE_COPY_XSAVE);
} else {
memcpy(&ustate->fxsave, &kstate->regs.fxsave,
sizeof(ustate->fxsave));
@@ -1049,6 +1049,7 @@ static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
* __copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer
* @to: membuf descriptor
* @fpstate: The fpstate buffer from which to copy
+ * @xfeatures: The mask of xfeatures to save (XSAVE mode only)
* @pkru_val: The PKRU value to store in the PKRU component
* @copy_mode: The requested copy mode
*
@@ -1059,7 +1060,8 @@ static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
* It supports partial copy but @to.pos always starts from zero.
*/
void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
- u32 pkru_val, enum xstate_copy_mode copy_mode)
+ u64 xfeatures, u32 pkru_val,
+ enum xstate_copy_mode copy_mode)
{
const unsigned int off_mxcsr = offsetof(struct fxregs_state, mxcsr);
struct xregs_state *xinit = &init_fpstate.regs.xsave;
@@ -1083,7 +1085,7 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
break;
case XSTATE_COPY_XSAVE:
- header.xfeatures &= fpstate->user_xfeatures;
+ header.xfeatures &= fpstate->user_xfeatures & xfeatures;
break;
}
@@ -1185,6 +1187,7 @@ void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
enum xstate_copy_mode copy_mode)
{
__copy_xstate_to_uabi_buf(to, tsk->thread.fpu.fpstate,
+ tsk->thread.fpu.fpstate->user_xfeatures,
tsk->thread.pkru, copy_mode);
}
@@ -43,7 +43,8 @@ enum xstate_copy_mode {
struct membuf;
extern void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
- u32 pkru_val, enum xstate_copy_mode copy_mode);
+ u64 xfeatures, u32 pkru_val,
+ enum xstate_copy_mode copy_mode);
extern void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
enum xstate_copy_mode mode);
extern int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf, u32 *pkru);
@@ -5382,17 +5382,6 @@ static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
return 0;
}
-static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
- struct kvm_xsave *guest_xsave)
-{
- if (fpstate_is_confidential(&vcpu->arch.guest_fpu))
- return;
-
- fpu_copy_guest_fpstate_to_uabi(&vcpu->arch.guest_fpu,
- guest_xsave->region,
- sizeof(guest_xsave->region),
- vcpu->arch.pkru);
-}
static void kvm_vcpu_ioctl_x86_get_xsave2(struct kvm_vcpu *vcpu,
u8 *state, unsigned int size)
@@ -5400,8 +5389,16 @@ static void kvm_vcpu_ioctl_x86_get_xsave2(struct kvm_vcpu *vcpu,
if (fpstate_is_confidential(&vcpu->arch.guest_fpu))
return;
- fpu_copy_guest_fpstate_to_uabi(&vcpu->arch.guest_fpu,
- state, size, vcpu->arch.pkru);
+ fpu_copy_guest_fpstate_to_uabi(&vcpu->arch.guest_fpu, state, size,
+ vcpu->arch.guest_fpu.fpstate->user_xfeatures,
+ vcpu->arch.pkru);
+}
+
+static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
+ struct kvm_xsave *guest_xsave)
+{
+ return kvm_vcpu_ioctl_x86_get_xsave2(vcpu, (void *)guest_xsave->region,
+ sizeof(guest_xsave->region));
}
static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
Plumb an xfeatures mask into __copy_xstate_to_uabi_buf() so that KVM can constrain which xfeatures are saved into the userspace buffer without having to modify the user_xfeatures field in KVM's guest_fpu state. KVM's ABI for KVM_GET_XSAVE{2} is that features that are not exposed to guest must not show up in the effective xstate_bv field of the buffer. Saving only the guest-supported xfeatures allows userspace to load the saved state on a different host with a fewer xfeatures, so long as the target host supports the xfeatures that are exposed to the guest. KVM currently sets user_xfeatures directly to restrict KVM_GET_XSAVE{2} to the set of guest-supported xfeatures, but doing so broke KVM's historical ABI for KVM_SET_XSAVE, which allows userspace to load any xfeatures that are supported by the *host*. Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/include/asm/fpu/api.h | 3 ++- arch/x86/kernel/fpu/core.c | 5 +++-- arch/x86/kernel/fpu/xstate.c | 7 +++++-- arch/x86/kernel/fpu/xstate.h | 3 ++- arch/x86/kvm/x86.c | 23 ++++++++++------------- 5 files changed, 22 insertions(+), 19 deletions(-)