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Thu, 08 Aug 2024 06:42:23 -0700 (PDT) From: Alejandro Vallejo To: Xen-devel Cc: Alejandro Vallejo , Jan Beulich , Andrew Cooper , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= Subject: [PATCH v2 2/2] x86/fpu: Split fpu_setup_fpu() in two Date: Thu, 8 Aug 2024 14:41:50 +0100 Message-ID: <20240808134150.29927-3-alejandro.vallejo@cloud.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240808134150.29927-1-alejandro.vallejo@cloud.com> References: <20240808134150.29927-1-alejandro.vallejo@cloud.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @cloud.com) X-ZM-MESSAGEID: 1723124573909116600 Content-Type: text/plain; charset="utf-8" It was trying to do too many things at once and there was no clear way of defining what it was meant to do.This commit splits the function in two. 1. A reset function, parameterized by the FCW value. FCW_RESET means to r= eset the state to power-on reset values, while FCW_DEFAULT means to reset t= o the default values present during vCPU creation. 2. A x87/SSE state loader (equivalent to the old function when it took a = data pointer). While at it, make sure the abridged tag is consistent with the manuals and start as 0xFF. Signed-off-by: Alejandro Vallejo --- v2: * Reworded comment about pre-Xen 4.1 migrations. * Reset abridged FTW to -1 (tag=3D0x5555), as per the manuals. * Undo const cast-away. * Split vcpu_reset_fpu() into vcpu_default_fpu() * vcpu_init_fpu() already exists. * Removed backticks from comments --- xen/arch/x86/domain.c | 7 ++-- xen/arch/x86/hvm/hvm.c | 27 ++++++++++---- xen/arch/x86/i387.c | 60 +++++++++++++++---------------- xen/arch/x86/include/asm/i387.h | 28 ++++++++++++--- xen/arch/x86/include/asm/xstate.h | 1 + 5 files changed, 77 insertions(+), 46 deletions(-) diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index d977ec71ca20..5af9e3e7a8b4 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -1186,9 +1186,10 @@ int arch_set_info_guest( is_pv_64bit_domain(d) ) v->arch.flags &=3D ~TF_kernel_mode; =20 - vcpu_setup_fpu(v, v->arch.xsave_area, - flags & VGCF_I387_VALID ? &c.nat->fpu_ctxt : NULL, - FCW_DEFAULT); + if ( flags & VGCF_I387_VALID ) + vcpu_setup_fpu(v, &c.nat->fpu_ctxt); + else + vcpu_default_fpu(v); =20 if ( !compat ) { diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index 6607dba562a4..83cb21884ce6 100644 --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -1164,10 +1164,25 @@ static int cf_check hvm_load_cpu_ctxt(struct domain= *d, hvm_domain_context_t *h) seg.attr =3D ctxt.ldtr_arbytes; hvm_set_segment_register(v, x86_seg_ldtr, &seg); =20 - /* Cover xsave-absent save file restoration on xsave-capable host. */ - vcpu_setup_fpu(v, xsave_enabled(v) ? NULL : v->arch.xsave_area, - ctxt.flags & XEN_X86_FPU_INITIALISED ? ctxt.fpu_regs : = NULL, - FCW_RESET); + /* + * On Xen 4.1 and later the FPU state is restored on later HVM context= in + * the migrate stream, so what we're doing here is initialising the FPU + * state for guests from even older versions of Xen. + * + * In particular: + * 1. If there's an XSAVE context later in the stream what we do her= e for + * the FPU doesn't matter because it'll be overriden later. + * 2. If there isn't and the guest didn't use extended states it's s= till + * fine because we have all the information we need here. + * 3. If there isn't and the guest DID use extended states (could've + * happened prior to Xen 4.1) then we're in a pickle because we h= ave + * to make up non-existing state. For this case we initialise the= FPU + * as using x87/SSE only because the rest of the state is gone. + */ + if ( ctxt.flags & XEN_X86_FPU_INITIALISED ) + vcpu_setup_fpu(v, &ctxt.fpu_regs); + else + vcpu_reset_fpu(v); =20 v->arch.user_regs.rax =3D ctxt.rax; v->arch.user_regs.rbx =3D ctxt.rbx; @@ -4007,9 +4022,7 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs= , uint16_t ip) v->arch.guest_table =3D pagetable_null(); } =20 - if ( v->arch.xsave_area ) - v->arch.xsave_area->xsave_hdr.xstate_bv =3D 0; - vcpu_setup_fpu(v, v->arch.xsave_area, NULL, FCW_RESET); + vcpu_reset_fpu(v); =20 arch_vcpu_regs_init(v); v->arch.user_regs.rip =3D ip; diff --git a/xen/arch/x86/i387.c b/xen/arch/x86/i387.c index fbb9d3584a3d..af5ae805998a 100644 --- a/xen/arch/x86/i387.c +++ b/xen/arch/x86/i387.c @@ -303,41 +303,37 @@ int vcpu_init_fpu(struct vcpu *v) return xstate_alloc_save_area(v); } =20 -void vcpu_setup_fpu(struct vcpu *v, struct xsave_struct *xsave_area, - const void *data, unsigned int fcw_default) +void vcpu_reset_fpu(struct vcpu *v) { - fpusse_t *fpu_sse =3D &v->arch.xsave_area->fpu_sse; - - ASSERT(!xsave_area || xsave_area =3D=3D v->arch.xsave_area); - - v->fpu_initialised =3D !!data; + v->fpu_initialised =3D false; + *v->arch.xsave_area =3D (struct xsave_struct) { + .fpu_sse =3D { + .mxcsr =3D MXCSR_DEFAULT, + .fcw =3D FCW_RESET, + .ftw =3D FTW_RESET, + }, + .xsave_hdr.xstate_bv =3D fcw =3D=3D X86_XCR0_X87, + }; +} =20 - if ( data ) - { - memcpy(fpu_sse, data, sizeof(*fpu_sse)); - if ( xsave_area ) - xsave_area->xsave_hdr.xstate_bv =3D XSTATE_FP_SSE; - } - else if ( xsave_area && fcw_default =3D=3D FCW_DEFAULT ) - { - xsave_area->xsave_hdr.xstate_bv =3D 0; - fpu_sse->mxcsr =3D MXCSR_DEFAULT; - } - else - { - memset(fpu_sse, 0, sizeof(*fpu_sse)); - fpu_sse->fcw =3D fcw_default; - fpu_sse->mxcsr =3D MXCSR_DEFAULT; - if ( v->arch.xsave_area ) - { - v->arch.xsave_area->xsave_hdr.xstate_bv &=3D ~XSTATE_FP_SSE; - if ( fcw_default !=3D FCW_DEFAULT ) - v->arch.xsave_area->xsave_hdr.xstate_bv |=3D X86_XCR0_X87; - } - } +void vcpu_default_fpu(struct vcpu *v) +{ + v->fpu_initialised =3D false; + *v->arch.xsave_area =3D (struct xsave_struct) { + .fpu_sse =3D { + .mxcsr =3D MXCSR_DEFAULT, + .fcw =3D FCW_DEFAULT, + }, + }; +} =20 - if ( xsave_area ) - xsave_area->xsave_hdr.xcomp_bv =3D 0; +void vcpu_setup_fpu(struct vcpu *v, const void *data) +{ + v->fpu_initialised =3D true; + *v->arch.xsave_area =3D (struct xsave_struct) { + .fpu_sse =3D *(const fpusse_t*)data, + .xsave_hdr.xstate_bv =3D XSTATE_FP_SSE, + }; } =20 /* Free FPU's context save area */ diff --git a/xen/arch/x86/include/asm/i387.h b/xen/arch/x86/include/asm/i38= 7.h index a783549db991..7a69577de45b 100644 --- a/xen/arch/x86/include/asm/i387.h +++ b/xen/arch/x86/include/asm/i387.h @@ -31,10 +31,30 @@ void vcpu_restore_fpu_nonlazy(struct vcpu *v, bool need= _stts); void vcpu_restore_fpu_lazy(struct vcpu *v); void vcpu_save_fpu(struct vcpu *v); void save_fpu_enable(void); - int vcpu_init_fpu(struct vcpu *v); -struct xsave_struct; -void vcpu_setup_fpu(struct vcpu *v, struct xsave_struct *xsave_area, - const void *data, unsigned int fcw_default); void vcpu_destroy_fpu(struct vcpu *v); + +/* + * Restore v's FPU to power-on reset values + * + * @param v vCPU containing the FPU + */ +void vcpu_reset_fpu(struct vcpu *v); + +/* + * Restore v's FPU to default values + * + * @param v vCPU containing the FPU + */ +void vcpu_default_fpu(struct vcpu *v); + +/* + * Load x87/SSE state into v's FPU + * + * Overrides the XSAVE header to set the state components to be x87 and SS= E. + * + * @param v vCPU containing the FPU + * @param data 512-octet blob for x87/SSE state + */ +void vcpu_setup_fpu(struct vcpu *v, const void *data); #endif /* __ASM_I386_I387_H */ diff --git a/xen/arch/x86/include/asm/xstate.h b/xen/arch/x86/include/asm/x= state.h index ebeb2a3dcaf9..6144ed6f8551 100644 --- a/xen/arch/x86/include/asm/xstate.h +++ b/xen/arch/x86/include/asm/xstate.h @@ -14,6 +14,7 @@ =20 #define FCW_DEFAULT 0x037f #define FCW_RESET 0x0040 +#define FTW_RESET 0xFF #define MXCSR_DEFAULT 0x1f80 =20 extern uint32_t mxcsr_mask; --=20 2.45.2