linux-kernel - [PATCH v6 07/21] x86/fpu: Provide fpu_enable_guest_xfd

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Date:   Fri,  7 Jan 2022 13:54:58 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     guang.zeng@...el.com, jing2.liu@...el.com, kevin.tian@...el.com,
        seanjc@...gle.com, tglx@...utronix.de, wei.w.wang@...el.com,
        yang.zhong@...el.com
Subject: [PATCH v6 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>
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
Message-Id: <20220105123532.12586-8-yang.zhong@...el.com>
[Remove unnecessary 32-bit check. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/include/asm/fpu/api.h |  1 +
 arch/x86/kernel/fpu/core.c     | 22 ++++++++++++++++++++++
 2 files changed, 23 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..64b2ee39bece 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -261,6 +261,28 @@ void fpu_free_guest_fpstate(struct fpu_guest *gfpu)
 }
 EXPORT_SYMBOL_GPL(fpu_free_guest_fpstate);
 
+/*
+  * fpu_enable_guest_xfd_features - Check xfeatures against guest perm and enable
+  * @guest_fpu:         Pointer to the guest FPU container
+  * @xfeatures:         Features requested by guest CPUID
+  *
+  * Enable all dynamic xfeatures according to guest perm and requested CPUID.
+  *
+  * Return: 0 on success, error code otherwise
+  */
+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;
+
+	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;
-- 
2.31.1