diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/fpu/core.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index e28ab0ecc537..0fdc807ae13f 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -14,6 +14,8 @@ #include <asm/traps.h> #include <asm/irq_regs.h> +#include <uapi/asm/kvm.h> + #include <linux/hardirq.h> #include <linux/pkeys.h> #include <linux/vmalloc.h> @@ -232,7 +234,20 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu) gfpu->fpstate = fpstate; gfpu->xfeatures = fpu_user_cfg.default_features; gfpu->perm = fpu_user_cfg.default_features; - gfpu->uabi_size = fpu_user_cfg.default_size; + + /* + * KVM sets the FP+SSE bits in the XSAVE header when copying FPU state + * to userspace, even when XSAVE is unsupported, so that restoring FPU + * state on a different CPU that does support XSAVE can cleanly load + * the incoming state using its natural XSAVE. In other words, KVM's + * uABI size may be larger than this host's default size. Conversely, + * the default size should never be larger than KVM's base uABI size; + * all features that can expand the uABI size must be opt-in. + */ + gfpu->uabi_size = sizeof(struct kvm_xsave); + if (WARN_ON_ONCE(fpu_user_cfg.default_size > gfpu->uabi_size)) + gfpu->uabi_size = fpu_user_cfg.default_size; + fpu_init_guest_permissions(gfpu); return true; |