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    Subject[PATCH v5 07/21] x86/fpu: Provide fpu_enable_guest_xfd_features() for KVM
    Date
    From: Sean Christopherson <seanjc@google.com>

    Provide a wrapper for expanding the guest fpstate buffer according
    to requested xfeatures. KVM wants to call this wrapper to manage
    any dynamic xstate used by the guest.

    Suggested-by: Sean Christopherson <seanjc@google.com>
    Signed-off-by: Sean Christopherson <seanjc@google.com>
    Signed-off-by: Kevin Tian <kevin.tian@intel.com>
    Signed-off-by: Yang Zhong <yang.zhong@intel.com>
    ---
    arch/x86/include/asm/fpu/api.h | 1 +
    arch/x86/kernel/fpu/core.c | 17 +++++++++++++++++
    2 files changed, 18 insertions(+)

    diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
    index d8c222290e68..1ed2a247a84e 100644
    --- a/arch/x86/include/asm/fpu/api.h
    +++ b/arch/x86/include/asm/fpu/api.h
    @@ -138,6 +138,7 @@ extern inline u64 xstate_get_guest_group_perm(void);
    extern bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu);
    extern void fpu_free_guest_fpstate(struct fpu_guest *gfpu);
    extern int fpu_swap_kvm_fpstate(struct fpu_guest *gfpu, bool enter_guest);
    +extern int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures);

    extern void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf, unsigned int size, u32 pkru);
    extern int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, u64 xcr0, u32 *vpkru);
    diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
    index a78bc547fc03..5b08d20a4005 100644
    --- a/arch/x86/kernel/fpu/core.c
    +++ b/arch/x86/kernel/fpu/core.c
    @@ -261,6 +261,23 @@ void fpu_free_guest_fpstate(struct fpu_guest *gfpu)
    }
    EXPORT_SYMBOL_GPL(fpu_free_guest_fpstate);

    +int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures)
    +{
    + lockdep_assert_preemption_enabled();
    +
    + /* Nothing to do if all requested features are already enabled. */
    + xfeatures &= ~guest_fpu->xfeatures;
    + if (!xfeatures)
    + return 0;
    +
    + /* Dynamic xfeatures are not supported with 32-bit kernels. */
    + if (!IS_ENABLED(CONFIG_X86_64))
    + return 0;
    +
    + return __xfd_enable_feature(xfeatures, guest_fpu);
    +}
    +EXPORT_SYMBOL_GPL(fpu_enable_guest_xfd_features);
    +
    int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)
    {
    struct fpstate *guest_fps = guest_fpu->fpstate;
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