The following commit has been merged into the x86/fpu branch of tip: Commit-ID: 75c52dad5e327605f1025f399dafdf4aaf5dae9c Gitweb: https://git.kernel.org/tip/75c52dad5e327605f1025f399dafdf4aaf5dae9c Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Fri, 22 Oct 2021 20:55:49 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Sat, 23 Oct 2021 13:14:50 +02:00 x86/fpu: Prepare for sanitizing KVM FPU code For the upcoming AMX support it's necessary to do a proper integration with KVM. To avoid more nasty hackery in KVM which violate encapsulation extend struct fpu and fpstate so the fpstate switching can be consolidated and simplified. Currently KVM allocates two FPU structs which are used for saving the user state of the vCPU thread and restoring the guest state when entering vcpu_run() and doing the reverse operation before leaving vcpu_run(). With the new fpstate mechanism this can be reduced to one extra buffer by swapping the fpstate pointer in current::thread::fpu. This makes the upcoming support for AMX and XFD simpler because then fpstate information (features, sizes, xfd) are always consistent and it does not require any nasty workarounds. Add fpu::__task_fpstate to save the regular fpstate pointer while the task is inside vcpu_run(). Add some state fields to fpstate to indicate the nature of the state. Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lkml.kernel.org/r/20211022185312.896403942@xxxxxxxxxxxxx --- arch/x86/include/asm/fpu/types.h | 44 ++++++++++++++++++++++++++++++- 1 file changed, 43 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h index a32be07..c72cb22 100644 --- a/arch/x86/include/asm/fpu/types.h +++ b/arch/x86/include/asm/fpu/types.h @@ -322,8 +322,32 @@ struct fpstate { /* @user_xfeatures: xfeatures valid in UABI buffers */ u64 user_xfeatures; + /* @is_valloc: Indicator for dynamically allocated state */ + unsigned int is_valloc : 1; + + /* @is_guest: Indicator for guest state (KVM) */ + unsigned int is_guest : 1; + + /* + * @is_confidential: Indicator for KVM confidential mode. + * The FPU registers are restored by the + * vmentry firmware from encrypted guest + * memory. On vmexit the FPU registers are + * saved by firmware to encrypted guest memory + * and the registers are scrubbed before + * returning to the host. So there is no + * content which is worth saving and restoring. + * The fpstate has to be there so that + * preemption and softirq FPU usage works + * without special casing. + */ + unsigned int is_confidential : 1; + + /* @in_use: State is in use */ + unsigned int in_use : 1; + /* @regs: The register state union for all supported formats */ - union fpregs_state regs; + union fpregs_state regs; /* @regs is dynamically sized! Don't add anything after @regs! */ } __aligned(64); @@ -364,6 +388,14 @@ struct fpu { struct fpstate *fpstate; /* + * @__task_fpstate: + * + * Pointer to an inactive struct fpstate. Initialized to NULL. Is + * used only for KVM support to swap out the regular task fpstate. + */ + struct fpstate *__task_fpstate; + + /* * @__fpstate: * * Initial in-memory storage for FPU registers which are saved in @@ -379,6 +411,16 @@ struct fpu { }; /* + * Guest pseudo FPU container + */ +struct fpu_guest { + /* + * @fpstate: Pointer to the allocated guest fpstate + */ + struct fpstate *fpstate; +}; + +/* * FPU state configuration data. Initialized at boot time. Read only after init. */ struct fpu_state_config {
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