[PATCH v6 01/26] 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
customize 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 v5:
* Moved fpstate_init_xstate() back to the header (again).
* Massaged the changelog.

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 | 11 ++++++++++-
 arch/x86/kernel/fpu/core.c          | 30 ++++++++++++++++++-----------
 arch/x86/kernel/fpu/init.c          |  2 +-
 arch/x86/kernel/fpu/xstate.c        |  3 +--
 arch/x86/kvm/x86.c                  |  2 +-
 5 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 5a18694a89b2..c7a64e2806a9 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -80,7 +80,7 @@ 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
@@ -88,6 +88,15 @@ static inline void fpstate_init_soft(struct swregs_state *soft) {}
 #endif
 extern void save_fpregs_to_fpstate(struct fpu *fpu);
 
+static inline void fpstate_init_xstate(struct xregs_state *xsave, u64 mask)
+{
+	/*
+	 * XRSTORS requires these bits set in xcomp_bv, or it will
+	 * trigger #GP:
+	 */
+	xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | mask;
+}
+
 /* Returns 0 or the negated trap number, which results in -EFAULT for #PF */
 #define user_insn(insn, output, input...)				\
 ({									\
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 7ada7bd03a32..d0c16f5a9aeb 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -203,15 +203,6 @@ void fpu_sync_fpstate(struct fpu *fpu)
 	fpregs_unlock();
 }
 
-static inline void fpstate_init_xstate(struct xregs_state *xsave)
-{
-	/*
-	 * XRSTORS requires these bits set in xcomp_bv, or it will
-	 * trigger #GP:
-	 */
-	xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | xfeatures_mask_all;
-}
-
 static inline void fpstate_init_fxstate(struct fxregs_state *fx)
 {
 	fx->cwd = 0x37f;
@@ -229,8 +220,25 @@ 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;
@@ -239,7 +247,7 @@ 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
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 64e29927cc32..e14c72bc8706 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/xstate.c b/arch/x86/kernel/fpu/xstate.c
index c8def1b7f8fb..d4fdceb9a309 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -395,8 +395,7 @@ 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 8ee7add0e763..3c3a52f6d490 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10273,7 +10273,7 @@ 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