[patch 10/31] x86/fpu: Cleanup xstate xcomp_bv initialization

Thomas Gleixner
2021-10-12T00:06:33Z

No point in having this duplicated all over the place with needlessly
different defines.

Provide a proper initialization function which initializes user buffers
properly and make KVM use it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/fpu/internal.h | 4 +++-
arch/x86/kernel/fpu/core.c | 35 +++++++++++++++++++----------------
arch/x86/kernel/fpu/init.c | 6 +++---
arch/x86/kernel/fpu/xstate.c | 8 +++-----
arch/x86/kernel/fpu/xstate.h | 18 ++++++++++++++++++
arch/x86/kvm/x86.c | 11 +++--------
6 files changed, 49 insertions(+), 33 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -80,7 +80,9 @@ static __always_inline __pure bool use_f

extern union fpregs_state init_fpstate;

-extern void fpstate_init(union fpregs_state *state);
+extern void fpstate_init_user(union fpregs_state *state);
+extern void fpu_init_fpstate_user(struct fpu *fpu);
+
#ifdef CONFIG_MATH_EMULATION
extern void fpstate_init_soft(struct swregs_state *soft);
#else
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -16,6 +16,8 @@
#include <linux/hardirq.h>
#include <linux/pkeys.h>

+#include "xstate.h"
+
#define CREATE_TRACE_POINTS
#include <asm/trace/fpu.h>

@@ -203,15 +205,6 @@ 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 unsigned int init_fpstate_copy_size(void)
{
if (!use_xsave())
@@ -238,23 +231,33 @@ static inline void fpstate_init_fstate(s
fp->fos = 0xffff0000u;
}

-void fpstate_init(union fpregs_state *state)
+/*
+ * Used in two places:
+ * 1) Early boot to setup init_fpstate for non XSAVE systems
+ * 2) fpu_init_fpstate_user() which is invoked from KVM
+ */
+void fpstate_init_user(union fpregs_state *state)
{
- if (!static_cpu_has(X86_FEATURE_FPU)) {
+ if (!cpu_feature_enabled(X86_FEATURE_FPU)) {
fpstate_init_soft(&state->soft);
return;
}

- memset(state, 0, fpu_kernel_xstate_size);
+ xstate_init_xcomp_bv(&state->xsave, xfeatures_mask_uabi());

- if (static_cpu_has(X86_FEATURE_XSAVES))
- fpstate_init_xstate(&state->xsave);
- if (static_cpu_has(X86_FEATURE_FXSR))
+ if (cpu_feature_enabled(X86_FEATURE_FXSR))
fpstate_init_fxstate(&state->fxsave);
else
fpstate_init_fstate(&state->fsave);
}
-EXPORT_SYMBOL_GPL(fpstate_init);
+
+#if IS_ENABLED(CONFIG_KVM)
+void fpu_init_fpstate_user(struct fpu *fpu)
+{
+ fpstate_init_user(&fpu->state);
+}
+EXPORT_SYMBOL_GPL(fpu_init_fpstate_user);
+#endif

/* Clone current's FPU state on fork */
int fpu_clone(struct task_struct *dst, unsigned long clone_flags)
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -121,10 +121,10 @@ static void __init fpu__init_system_mxcs
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.)
+ * Set up the legacy init FPU context. Will be updated when the
+ * CPU supports XSAVE[S].
*/
- fpstate_init(&init_fpstate);
+ fpstate_init_user(&init_fpstate);

fpu__init_system_mxcsr();
}
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -15,10 +15,10 @@
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
#include <asm/fpu/regset.h>
-#include <asm/fpu/xstate.h>

#include <asm/tlbflush.h>
-#include <asm/cpufeature.h>
+
+#include "xstate.h"

/*
* Although we spell it out in here, the Processor Trace
@@ -389,9 +389,7 @@ static void __init setup_init_fpu_buf(vo
setup_xstate_features();
print_xstate_features();

- if (boot_cpu_has(X86_FEATURE_XSAVES))
- init_fpstate.xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
- xfeatures_mask_all;
+ xstate_init_xcomp_bv(&init_fpstate.xsave, xfeatures_mask_all);

/*
* Init all the features state with header.xfeatures being 0x0
--- /dev/null
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __X86_KERNEL_FPU_XSTATE_H
+#define __X86_KERNEL_FPU_XSTATE_H
+
+#include <asm/cpufeature.h>
+#include <asm/fpu/xstate.h>
+
+static inline void xstate_init_xcomp_bv(struct xregs_state *xsave, u64 mask)
+{
+ /*
+ * XRSTORS requires these bits set in xcomp_bv, or it will
+ * trigger #GP:
+ */
+ if (cpu_feature_enabled(X86_FEATURE_XSAVES))
+ xsave->header.xcomp_bv = mask | XCOMP_BV_COMPACTED_FORMAT;
+}
+
+#endif
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10612,14 +10612,6 @@ static int sync_regs(struct kvm_vcpu *vc

static void fx_init(struct kvm_vcpu *vcpu)
{
- if (!vcpu->arch.guest_fpu)
- return;
-
- fpstate_init(&vcpu->arch.guest_fpu->state);
- if (boot_cpu_has(X86_FEATURE_XSAVES))
- vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =
- host_xcr0 | XSTATE_COMPACTION_ENABLED;
-
/*
* Ensure guest xcr0 is valid for loading
*/
@@ -10704,6 +10696,9 @@ int kvm_arch_vcpu_create(struct kvm_vcpu
pr_err("kvm: failed to allocate vcpu's fpu\n");
goto free_user_fpu;
}
+
+ fpu_init_fpstate_user(vcpu->arch.user_fpu);
+ fpu_init_fpstate_user(vcpu->arch.guest_fpu);
fx_init(vcpu);

vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);