linux-kernel - [PATCH v5 07/21] x86/fpu: Provide fpu_enable_guest_xfd

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Date:   Wed,  5 Jan 2022 04:35:18 -0800
From:   Yang Zhong <yang.zhong@...el.com>
To:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, pbonzini@...hat.com, corbet@....net,
        shuah@...nel.org, seanjc@...gle.com
Cc:     jun.nakajima@...el.com, kevin.tian@...el.com,
        jing2.liu@...ux.intel.com, jing2.liu@...el.com,
        guang.zeng@...el.com, wei.w.wang@...el.com, yang.zhong@...el.com
Subject: [PATCH v5 07/21] x86/fpu: Provide fpu_enable_guest_xfd_features() for KVM

From: Sean Christopherson <seanjc@...gle.com>

Provide a wrapper for expanding the guest fpstate buffer according
to requested xfeatures. KVM wants to call this wrapper to manage
any dynamic xstate used by the guest.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Kevin Tian <kevin.tian@...el.com>
Signed-off-by: Yang Zhong <yang.zhong@...el.com>
---
 arch/x86/include/asm/fpu/api.h |  1 +
 arch/x86/kernel/fpu/core.c     | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index d8c222290e68..1ed2a247a84e 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -138,6 +138,7 @@ extern inline u64 xstate_get_guest_group_perm(void);
 extern bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu);
 extern void fpu_free_guest_fpstate(struct fpu_guest *gfpu);
 extern int fpu_swap_kvm_fpstate(struct fpu_guest *gfpu, bool enter_guest);
+extern int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures);
 
 extern void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf, unsigned int size, u32 pkru);
 extern int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, u64 xcr0, u32 *vpkru);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index a78bc547fc03..5b08d20a4005 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -261,6 +261,23 @@ void fpu_free_guest_fpstate(struct fpu_guest *gfpu)
 }
 EXPORT_SYMBOL_GPL(fpu_free_guest_fpstate);
 
+int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures)
+{
+	lockdep_assert_preemption_enabled();
+
+	/* Nothing to do if all requested features are already enabled. */
+	xfeatures &= ~guest_fpu->xfeatures;
+	if (!xfeatures)
+		return 0;
+
+	/* Dynamic xfeatures are not supported with 32-bit kernels. */
+	if (!IS_ENABLED(CONFIG_X86_64))
+		return 0;
+
+	return __xfd_enable_feature(xfeatures, guest_fpu);
+}
+EXPORT_SYMBOL_GPL(fpu_enable_guest_xfd_features);
+
 int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)
 {
 	struct fpstate *guest_fps = guest_fpu->fpstate;