[PATCH v5 01/28] x86/fpu/xstate: Modify the initialization helper to handle both static and dynamic buffers

[Chang S. Bae]

Have the function initializing the xstate buffer take a struct fpu *
pointer in preparation for dynamic state buffer support.

init_fpstate is a special case, which is indicated by a null pointer
parameter to fpstate_init().

Also, fpstate_init_xstate() now accepts the state component bitmap to
configure XCOMP_BV for the compacted format.

No functional change.

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 v4:
* Added a proper function description. (Borislav Petkov)
* Added the likely() statement as a null pointer is a special case.

Changes from v3:
* Updated the changelog. (Borislav Petkov)
* Updated the function comment to use kernel-doc style. (Borislav Petkov)

Changes from v2:
* Updated the changelog with task->fpu removed. (Borislav Petkov)
---
 arch/x86/include/asm/fpu/internal.h |  6 +++---
 arch/x86/kernel/fpu/core.c          | 23 ++++++++++++++++++++---
 arch/x86/kernel/fpu/init.c          |  2 +-
 arch/x86/kernel/fpu/regset.c        |  2 +-
 arch/x86/kernel/fpu/xstate.c        |  3 +--
 arch/x86/kvm/x86.c                  |  2 +-
 6 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 8d33ad80704f..d81d8c407dc0 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -80,20 +80,20 @@ static __always_inline __pure bool use_fxsr(void)
 
 extern union fpregs_state init_fpstate;
 
-extern void fpstate_init(union fpregs_state *state);
+extern void fpstate_init(struct fpu *fpu);
 #ifdef CONFIG_MATH_EMULATION
 extern void fpstate_init_soft(struct swregs_state *soft);
 #else
 static inline void fpstate_init_soft(struct swregs_state *soft) {}
 #endif
 
-static inline void fpstate_init_xstate(struct xregs_state *xsave)
+static inline void fpstate_init_xstate(struct xregs_state *xsave, u64 xcomp_mask)
 {
 	/*
 	 * XRSTORS requires these bits set in xcomp_bv, or it will
 	 * trigger #GP:
 	 */
-	xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | xfeatures_mask_all;
+	xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | xcomp_mask;
 }
 
 static inline void fpstate_init_fxstate(struct fxregs_state *fx)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 571220ac8bea..52f886477b07 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -192,8 +192,25 @@ static inline void fpstate_init_fstate(struct fregs_state *fp)
 	fp->fos = 0xffff0000u;
 }
 
-void fpstate_init(union fpregs_state *state)
+/**
+ *
+ * fpstate_init() - initialize the xstate buffer
+ *
+ * If @fpu is NULL, initialize init_fpstate.
+ *
+ * @fpu:	A struct fpu * pointer
+ *
+ * Returns nothing.
+ */
+void fpstate_init(struct fpu *fpu)
 {
+	union fpregs_state *state;
+
+	if (likely(fpu))
+		state = &fpu->state;
+	else
+		state = &init_fpstate;
+
 	if (!static_cpu_has(X86_FEATURE_FPU)) {
 		fpstate_init_soft(&state->soft);
 		return;
@@ -202,7 +219,7 @@ void fpstate_init(union fpregs_state *state)
 	memset(state, 0, fpu_kernel_xstate_size);
 
 	if (static_cpu_has(X86_FEATURE_XSAVES))
-		fpstate_init_xstate(&state->xsave);
+		fpstate_init_xstate(&state->xsave, xfeatures_mask_all);
 	if (static_cpu_has(X86_FEATURE_FXSR))
 		fpstate_init_fxstate(&state->fxsave);
 	else
@@ -262,7 +279,7 @@ static void fpu__initialize(struct fpu *fpu)
 	WARN_ON_FPU(fpu != &current->thread.fpu);
 
 	set_thread_flag(TIF_NEED_FPU_LOAD);
-	fpstate_init(&fpu->state);
+	fpstate_init(fpu);
 	trace_x86_fpu_init_state(fpu);
 }
 
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 701f196d7c68..74e03e3bc20f 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -124,7 +124,7 @@ static void __init fpu__init_system_generic(void)
 	 * Set up the legacy init FPU context. (xstate init might overwrite this
 	 * with a more modern format, if the CPU supports it.)
 	 */
-	fpstate_init(&init_fpstate);
+	fpstate_init(NULL);
 
 	fpu__init_system_mxcsr();
 }
diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c
index c413756ba89f..4c4d9059ff36 100644
--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -144,7 +144,7 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
 	 * In case of failure, mark all states as init:
 	 */
 	if (ret)
-		fpstate_init(&fpu->state);
+		fpstate_init(fpu);
 
 	return ret;
 }
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index a85c64000218..767ad6b008c2 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -457,8 +457,7 @@ static void __init setup_init_fpu_buf(void)
 	print_xstate_features();
 
 	if (boot_cpu_has(X86_FEATURE_XSAVES))
-		init_fpstate.xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
-						     xfeatures_mask_all;
+		fpstate_init_xstate(&init_fpstate.xsave, xfeatures_mask_all);
 
 	/*
 	 * Init all the features state with header.xfeatures being 0x0
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bbc4e04e67ad..9af0a3c52b62 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10248,7 +10248,7 @@ static void fx_init(struct kvm_vcpu *vcpu)
 	if (!vcpu->arch.guest_fpu)
 		return;
 
-	fpstate_init(&vcpu->arch.guest_fpu->state);
+	fpstate_init(vcpu->arch.guest_fpu);
 	if (boot_cpu_has(X86_FEATURE_XSAVES))
 		vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =
 			host_xcr0 | XSTATE_COMPACTION_ENABLED;
-- 
2.17.1