[PATCH v4 11/22] x86/fpu/xstate: Update the xstate save function to support dynamic states

[Chang S. Bae]

Extend copy_xregs_to_kernel() to receive a mask argument of which states to
save, in preparation for dynamic user state handling.

Update KVM to set a valid fpu->state_mask, so it can continue to share with
the core code.

Signed-off-by: Chang S. Bae <chang.seok....@intel.com>
Reviewed-by: Len Brown <len.br...@intel.com>
Cc: x...@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: k...@vger.kernel.org
---
Changes from v3:
* Updated the changelog. (Borislav Petkov)
* Made the code change more reviewable.

Changes from v2:
* Updated the changelog to clarify the KVM code changes.
---
 arch/x86/include/asm/fpu/internal.h | 3 +--
 arch/x86/kernel/fpu/core.c          | 2 +-
 arch/x86/kvm/x86.c                  | 9 +++++++--
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h 
b/arch/x86/include/asm/fpu/internal.h
index e4afc1831e29..f964f3efc92e 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -317,9 +317,8 @@ static inline void copy_kernel_to_xregs_booting(struct 
xregs_state *xstate)
 /*
  * Save processor xstate to xsave area.
  */
-static inline void copy_xregs_to_kernel(struct xregs_state *xstate)
+static inline void copy_xregs_to_kernel(struct xregs_state *xstate, u64 mask)
 {
-       u64 mask = xfeatures_mask_all;
        u32 lmask = mask;
        u32 hmask = mask >> 32;
        int err;
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index dc20eabb072d..ad1ac80f98ef 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -98,7 +98,7 @@ EXPORT_SYMBOL(irq_fpu_usable);
 int copy_fpregs_to_fpstate(struct fpu *fpu)
 {
        if (likely(use_xsave())) {
-               copy_xregs_to_kernel(&fpu->state->xsave);
+               copy_xregs_to_kernel(&fpu->state->xsave, fpu->state_mask);
 
                /*
                 * AVX512 state is tracked here because its use is
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c10122547ecd..ca2c0574acf2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9275,11 +9275,16 @@ static void kvm_save_current_fpu(struct fpu *fpu)
         * KVM does not support dynamic user states yet. Assume the buffer
         * always has the minimum size.
         */
-       if (test_thread_flag(TIF_NEED_FPU_LOAD))
+       if (test_thread_flag(TIF_NEED_FPU_LOAD)) {
                memcpy(fpu->state, current->thread.fpu.state,
                       get_xstate_config(XSTATE_MIN_SIZE));
-       else
+       } else {
+               struct fpu *src_fpu = &current->thread.fpu;
+
+               if (fpu->state_mask != src_fpu->state_mask)
+                       fpu->state_mask = src_fpu->state_mask;
                copy_fpregs_to_fpstate(fpu);
+       }
 }
 
 /* Swap (qemu) user FPU context for the guest FPU context. */
-- 
2.17.1