On Fri, Mar 07, 2025 at 10:14:19AM -0800, Dave Hansen wrote: >On 3/7/25 08:41, Chao Gao wrote: >> From: Yang Weijiang <weijiang.yang@xxxxxxxxx> >> >> Use the new fpu_guest_cfg to initialize guest permissions. > >Background, please. > >What are the guest permissions currently set to? Why does it need to change? Ok. Will add: Currently, fpu->guest_perm is copied from fpu->perm, which is derived from fpu_kernel_cfg. To separate the guest FPU from the kernel FPU, switch to use the new fpu_guest_cfg to initialize guest permissions. This ensures that any future changes to fpu_guest_cfg will automatically update the guest permissions The __user_state_size is tied to existing uAPIs, so it remains unchanged. > >> Note fpu_guest_cfg and fpu_kernel_cfg remain the same for now. So there >> is no functional change. >> >> Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx> >> [Gao Chao: Extrace this from the previous patch ] >> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx> >> --- >> arch/x86/kernel/fpu/core.c | 11 +++++++++-- >> 1 file changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c >> index b0c1ef40d105..d7ae684adbad 100644 >> --- a/arch/x86/kernel/fpu/core.c >> +++ b/arch/x86/kernel/fpu/core.c >> @@ -534,8 +534,15 @@ void fpstate_reset(struct fpu *fpu) >> fpu->perm.__state_perm = fpu_kernel_cfg.default_features; >> fpu->perm.__state_size = fpu_kernel_cfg.default_size; >> fpu->perm.__user_state_size = fpu_user_cfg.default_size; >> - /* Same defaults for guests */ >> - fpu->guest_perm = fpu->perm; >> + >> + /* Guest permission settings */ >> + fpu->guest_perm.__state_perm = fpu_guest_cfg.default_features; >> + fpu->guest_perm.__state_size = fpu_guest_cfg.default_size; >> + /* >> + * Set guest's __user_state_size to fpu_user_cfg.default_size so that >> + * existing uAPIs can still work. >> + */ > >I suspect that readers here will understand that this line: > >> + fpu->guest_perm.__user_state_size = fpu_user_cfg.default_size; >> } > >means "Set guest's __user_state_size to fpu_user_cfg.default_size". The >comment basically just literally restates what the code does. That part >of the comment doesn't add value. Will drop this useless comment.
