[PATCH v6a 6/8] x86/fpu: Remove xfd argument from __fpstate_reset()

Chao Gao
2025-05-09T08:16:20Z

The initial values for fpstate::xfd differ between guest and host fpstates.
Currently, the initial values are passed as an argument to
__fpstate_reset(). But, __fpstate_reset() already assigns different default
features and sizes based on the type of fpstates (i.e., guest or host). So,
handle fpstate::xfd in a similar way to highlight the differences in the
initial xfd value between guest and host fpstates

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Chao Gao <chao.gao@intel.com>
Link: https://lore.kernel.org/all/aBuf7wiiDT0Wflhk@google.com/
---
v6a: new.

Note: this quick revision is just intended to ensure that the feedback
has been properly addressed.

arch/x86/kernel/fpu/core.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 0d501bd25d79..a3cafed350e0 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -211,7 +211,7 @@ void fpu_reset_from_exception_fixup(void)
}

#if IS_ENABLED(CONFIG_KVM)
-static void __fpstate_reset(struct fpstate *fpstate, u64 xfd);
+static void __fpstate_reset(struct fpstate *fpstate);

static void fpu_lock_guest_permissions(void)
{
@@ -246,8 +246,7 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
fpstate->is_valloc = true;
fpstate->is_guest = true;

- /* Leave xfd to 0 (the reset value defined by spec) */
- __fpstate_reset(fpstate, 0);
+ __fpstate_reset(fpstate);
fpstate_init_user(fpstate);

gfpu->fpstate = fpstate;
@@ -536,7 +535,7 @@ void fpstate_init_user(struct fpstate *fpstate)
fpstate_init_fstate(fpstate);
}

-static void __fpstate_reset(struct fpstate *fpstate, u64 xfd)
+static void __fpstate_reset(struct fpstate *fpstate)
{
/*
* Initialize sizes and feature masks. Supervisor features and
@@ -546,21 +545,23 @@ static void __fpstate_reset(struct fpstate *fpstate, u64 xfd)
if (fpstate->is_guest) {
fpstate->size = guest_default_cfg.size;
fpstate->xfeatures = guest_default_cfg.features;
+ /* Leave xfd to 0 (the reset value defined by spec) */
+ fpstate->xfd = 0;
} else {
fpstate->size = fpu_kernel_cfg.default_size;
fpstate->xfeatures = fpu_kernel_cfg.default_features;
+ fpstate->xfd = init_fpstate.xfd;
}

fpstate->user_size = fpu_user_cfg.default_size;
fpstate->user_xfeatures = fpu_user_cfg.default_features;
- fpstate->xfd = xfd;
}

void fpstate_reset(struct fpu *fpu)
{
/* Set the fpstate pointer to the default fpstate */
fpu->fpstate = &fpu->__fpstate;
- __fpstate_reset(fpu->fpstate, init_fpstate.xfd);
+ __fpstate_reset(fpu->fpstate);

/* Initialize the permission related info in fpu */
fpu->perm.__state_perm = fpu_kernel_cfg.default_features;
--
2.47.1