[PATCH v9 01/26] x86/fpu/xstate: Modify the initialization helper to handle both static and dynamic buffers

Chang S. Bae
2021-07-30T15:06:10Z

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@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kvm@vger.kernel.org
---
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 | 28 +++++++++++++++++-----------
arch/x86/kernel/fpu/init.c | 2 +-
arch/x86/kernel/fpu/xstate.c | 3 +--
arch/x86/kvm/x86.c | 2 +-
5 files changed, 30 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..c0098f8422de 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 +220,23 @@ 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
+ */
+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 +245,7 @@ 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 a4fd10604f72..76a4e5e274d8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10599,7 +10599,7 @@ 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