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Wed, 2 Apr 2025 03:16:15 +0000 Date: Wed, 2 Apr 2025 11:16:02 +0800 From: Chao Gao To: "Chang S. 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Bae wrote: >On 3/18/2025 8:31 AM, Chao Gao wrote: >> >> @@ -807,9 +811,11 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) >> /* Clean out dynamic features from default */ >> fpu_kernel_cfg.default_features = fpu_kernel_cfg.max_features; >> fpu_kernel_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC; >> + fpu_kernel_cfg.guest_default_features = fpu_kernel_cfg.default_features; >> fpu_user_cfg.default_features = fpu_user_cfg.max_features; >> fpu_user_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC; >> + fpu_user_cfg.guest_default_features = fpu_user_cfg.default_features; > >And you'll add up this on patch7: > > + /* Clean out guest-only features from default */ > + fpu_kernel_cfg.default_features &= ~XFEATURE_MASK_SUPERVISOR_GUEST; > > >I'm not sure this overall hunk is entirely clear. I agree that this hunk is unclear, and your version is much better. > > >Taking a step back, we currently define three types of xfeature sets: > > 1. 'default_features' in a task-inlined buffer > 2. 'max_features' in an extended buffer > 3. 'independent_features' in a separate buffer (only for LBR) > >The VCPU fpstate has so far followed (1) and (2). Now, since we're >introducing divergence at (1), you've named it guest_default_features: > > 'default_features' < 'guest_default_features' < 'max_features' > >I don’t see a strong reason against introducing this new field, as 'guest' >already implies the VCPU state. However, rather than directly modifying or >extending struct fpu_state_config — which may not align well with VCPU FPU >properties — a dedicated struct could provide a cleaner and more structured >alternative: > > struct vcpu_fpu_config { > unsigned int size; > unsigned int user_size; > u64 features; > u64 user_features; > } guest_default_cfg; Your suggestion looks good to me, and I can definitely incorporate the change in the next version. Thanks a lot, Chang.