[PATCH v6 09/26] x86/fpu/xstate: Update the XSTATE save function to support dynamic states

["Chang S. Bae" <chang.seok.bae@xxxxxxxxx>]

Extend os_xsave() 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.bae@xxxxxxxxx>
Reviewed-by: Len Brown <len.brown@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
---
Changes from v5:
* Adjusted the changelog and code for the new base code.

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/kernel/fpu/signal.c        | 2 +-
 arch/x86/kvm/x86.c                  | 9 +++++++--
 4 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index d2fc19c0e457..263e349ff85a 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -298,9 +298,8 @@ static inline void os_xrstor_booting(struct xregs_state *xstate)
  * Uses either XSAVE or XSAVEOPT or XSAVES depending on the CPU features
  * and command line options. The choice is permanent until the next reboot.
  */
-static inline void os_xsave(struct xregs_state *xstate)
+static inline void os_xsave(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 0c28e3d389e5..5b50bcf9f4ff 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -99,7 +99,7 @@ EXPORT_SYMBOL(irq_fpu_usable);
 void save_fpregs_to_fpstate(struct fpu *fpu)
 {
 	if (likely(use_xsave())) {
-		os_xsave(&fpu->state->xsave);
+		os_xsave(&fpu->state->xsave, fpu->state_mask);
 
 		/*
 		 * AVX512 state is tracked here because its use is
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 2f35aada2007..f70f84d53442 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -365,7 +365,7 @@ static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
 		 * the right place in memory. It's ia32 mode. Shrug.
 		 */
 		if (xfeatures_mask_supervisor())
-			os_xsave(&fpu->state->xsave);
+			os_xsave(&fpu->state->xsave, fpu->state_mask);
 		set_thread_flag(TIF_NEED_FPU_LOAD);
 	}
 	__fpu_invalidate_fpregs_state(fpu);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3c8b6080a253..57c1fa628a20 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9637,11 +9637,16 @@ 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;
 		save_fpregs_to_fpstate(fpu);
+	}
 }
 
 /* Swap (qemu) user FPU context for the guest FPU context. */
-- 
2.17.1