Messages in this thread Patch in this message |  | | From | "Chang S. Bae" <> | Subject | [PATCH v5 10/28] x86/fpu/xstate: Define the scope of the initial xstate data | Date | Sun, 23 May 2021 12:32:41 -0700 |
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init_fpstate is used to record the initial xstate value and covers all the states. But it is wasteful to cover large states all with trivial initial data.
Limit init_fpstate by clarifying its size and coverage, which are all but dynamic user states. The dynamic states are assumed to be large but having initial data with zeros.
Expand copy_xregs_to_kernel_booting() to receive a mask argument of which states to save.
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Reviewed-by: Len Brown <len.brown@intel.com> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v3: * Removed the helper functions. (Borislav Petkov) * Removed 'no functional change' in the changelog. (Borislav Petkov) * Updated the code comment. * Moved out the other initialization changes into the previous patch.
Changes from v2: * Updated the changelog for clarification. * Updated the code comments. --- arch/x86/include/asm/fpu/internal.h | 3 +-- arch/x86/kernel/fpu/core.c | 13 ++++++++++--- arch/x86/kernel/fpu/xstate.c | 11 +++++++++-- 3 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 46cb51ef4d17..e4afc1831e29 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -272,9 +272,8 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu) * This function is called only during boot time when x86 caps are not set * up and alternative can not be used yet. */ -static inline void copy_xregs_to_kernel_booting(struct xregs_state *xstate) +static inline void copy_xregs_to_kernel_booting(struct xregs_state *xstate, u64 mask) { - u64 mask = xfeatures_mask_all; u32 lmask = mask; u32 hmask = mask >> 32; int err; diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 918930553290..2584a2922fea 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -21,7 +21,10 @@ /* * Represents the initial FPU state. It's mostly (but not completely) zeroes, - * depending on the FPU hardware format: + * depending on the FPU hardware format. + * + * The dynamic user states are excluded as they are large but having initial + * values with zeros. */ union fpregs_state init_fpstate __read_mostly; @@ -213,9 +216,13 @@ void fpstate_init(struct fpu *fpu) mask = fpu->state_mask; size = get_xstate_size(fpu->state_mask); } else { + /* + * init_fpstate excludes the dynamic user states as they are + * large but having initial values with zeros. + */ state = &init_fpstate; - mask = xfeatures_mask_all; - size = get_xstate_config(XSTATE_MAX_SIZE); + mask = (xfeatures_mask_all & ~xfeatures_mask_user_dynamic); + size = get_xstate_config(XSTATE_MIN_SIZE); } if (!static_cpu_has(X86_FEATURE_FPU)) { diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 0e3f93b03b3f..773f594bd730 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -552,6 +552,7 @@ static void __init print_xstate_offset_size(void) static void __init setup_init_fpu_buf(void) { static int on_boot_cpu __initdata = 1; + u64 mask; WARN_ON_FPU(!on_boot_cpu); on_boot_cpu = 0; @@ -562,8 +563,14 @@ static void __init setup_init_fpu_buf(void) setup_xstate_features(); print_xstate_features(); + /* + * Exclude the dynamic user states as they are large but having + * initial values with zeros. + */ + mask = xfeatures_mask_all & ~xfeatures_mask_user_dynamic; + if (boot_cpu_has(X86_FEATURE_XSAVES)) - fpstate_init_xstate(&init_fpstate.xsave, xfeatures_mask_all); + fpstate_init_xstate(&init_fpstate.xsave, mask); /* * Init all the features state with header.xfeatures being 0x0 @@ -574,7 +581,7 @@ static void __init setup_init_fpu_buf(void) * Dump the init state again. This is to identify the init state * of any feature which is not represented by all zero's. */ - copy_xregs_to_kernel_booting(&init_fpstate.xsave); + copy_xregs_to_kernel_booting(&init_fpstate.xsave, mask); } static int xfeature_uncompacted_offset(int xfeature_nr) -- 2.17.1
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