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Subject[PATCH 02/19] x86/fpu: Prepare KVM for dynamically enabled states
Date
From: Thomas Gleixner <tglx@linutronix.de>

Add more fields for tracking per-vCPU permissions for dynamic XSTATE
components:

- user_xfeatures

Track which features are currently enabled for the vCPU

- user_perm

Copied from guest_perm of the group leader thread. The first
vCPU which does the copy locks the guest_perm

- realloc_request

KVM sets this field to request dynamically-enabled features
which require reallocation of @fpstate

Initialize those fields properly.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
---
arch/x86/include/asm/fpu/types.h | 23 +++++++++++++++++++++++
arch/x86/kernel/fpu/core.c | 26 +++++++++++++++++++++++++-
2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 6ddf80637697..861cffca3209 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -504,6 +504,29 @@ struct fpu {
* Guest pseudo FPU container
*/
struct fpu_guest {
+ /*
+ * @user_xfeatures: xfeature bitmap of features which are
+ * currently enabled for the guest vCPU.
+ */
+ u64 user_xfeatures;
+
+ /*
+ * @user_perm: xfeature bitmap of features which are
+ * permitted to be enabled for the guest
+ * vCPU.
+ */
+ u64 user_perm;
+
+ /*
+ * @realloc_request: xfeature bitmap of features which are
+ * requested to be enabled dynamically
+ * which requires reallocation of @fpstate
+ *
+ * Set by an intercept handler and
+ * evaluated in fpu_swap_kvm_fpstate()
+ */
+ u64 realloc_request;
+
/*
* @fpstate: Pointer to the allocated guest fpstate
*/
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index ab19b3d8b2f7..fe592799508c 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -201,6 +201,26 @@ void fpu_reset_from_exception_fixup(void)
#if IS_ENABLED(CONFIG_KVM)
static void __fpstate_reset(struct fpstate *fpstate);

+static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
+{
+ struct fpu_state_perm *fpuperm;
+ u64 perm;
+
+ if (!IS_ENABLED(CONFIG_X86_64))
+ return;
+
+ spin_lock_irq(&current->sighand->siglock);
+ fpuperm = &current->group_leader->thread.fpu.guest_perm;
+ perm = fpuperm->__state_perm;
+
+ /* First fpstate allocation locks down permissions. */
+ WRITE_ONCE(fpuperm->__state_perm, perm | FPU_GUEST_PERM_LOCKED);
+
+ spin_unlock_irq(&current->sighand->siglock);
+
+ gfpu->user_perm = perm & ~FPU_GUEST_PERM_LOCKED;
+}
+
bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
{
struct fpstate *fpstate;
@@ -216,7 +236,11 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
fpstate->is_valloc = true;
fpstate->is_guest = true;

- gfpu->fpstate = fpstate;
+ gfpu->fpstate = fpstate;
+ gfpu->user_xfeatures = fpu_user_cfg.default_features;
+ gfpu->user_perm = fpu_user_cfg.default_features;
+ fpu_init_guest_permissions(gfpu);
+
return true;
}
EXPORT_SYMBOL_GPL(fpu_alloc_guest_fpstate);
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