Re: [PATCH v4] KVM: x86: emulate FXSAVE and FXRSTOR

[Fengguang Wu]

CC Xiaolong.

On Wed, Nov 09, 2016 at 07:46:28PM +0100, Radim KrÄmÃÅ wrote:
> 2016-11-10 02:42+0800, kbuild test robot:
> > Hi Radim,
>
> And I even replied to the series, so this would happen ...
> Btw. would the tool recognize it if the header was [PATCH v4 4/4]?
>
> > [auto build test ERROR on kvm/linux-next]
> > [also build test ERROR on v4.9-rc4 next-20161109]
> > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> >
> > url:    https://github.com/0day-ci/linux/commits/Radim-Kr-m/KVM-x86-emulate-FXSAVE-and-FXRSTOR/20161110-021048
> > base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
> > config: x86_64-randconfig-x018-201645 (attached as .config)
> > compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
> > reproduce:
> >         # save the attached .config to linux build tree
> >         make ARCH=x86_64
> >
> > All errors (new ones prefixed by >>):
> >
> >    arch/x86/kvm/emulate.c: In function 'em_fxsave':
> > >> arch/x86/kvm/emulate.c:3910:7: error: implicit declaration of function 'asm_safe' [-Werror=implicit-function-declaration]
> >      rc = asm_safe("fxsave %[fx]", , [fx] "+m"(fx_state));
> >           ^~~~~~~~
> > >> arch/x86/kvm/emulate.c:3910:32: error: expected expression before ',' token
> >      rc = asm_safe("fxsave %[fx]", , [fx] "+m"(fx_state));
> >                                    ^
> > >> arch/x86/kvm/emulate.c:3910:35: error: 'fx' undeclared (first use in this function)
> >      rc = asm_safe("fxsave %[fx]", , [fx] "+m"(fx_state));
> >                                       ^~
> >    arch/x86/kvm/emulate.c:3910:35: note: each undeclared identifier is reported only once for each function it appears in
> >    arch/x86/kvm/emulate.c: In function 'fxrstor_fixup':
> >    arch/x86/kvm/emulate.c:3931:32: error: expected expression before ',' token
> >      rc = asm_safe("fxsave %[fx]", , [fx] "+m"(old));
> >                                    ^
> >    arch/x86/kvm/emulate.c:3931:35: error: 'fx' undeclared (first use in this function)
> >      rc = asm_safe("fxsave %[fx]", , [fx] "+m"(old));
> >                                       ^~
> >    arch/x86/kvm/emulate.c: In function 'em_fxrstor':
> > >> arch/x86/kvm/emulate.c:3977:34: error: expected expression before ':' token
> >       rc = asm_safe("fxrstor %[fx]", : [fx] "m"(fx_state));
> >                                      ^
> >    arch/x86/kvm/emulate.c: At top level:
> > >> arch/x86/kvm/emulate.c:4336:12: error: 'Aligned16' undeclared here (not in a function)
> >      I(ModRM | Aligned16, em_fxsave),
> >                ^
> >    arch/x86/kvm/emulate.c:4185:31: note: in definition of macro 'I'
> >     #define I(_f, _e) { .flags = (_f), .u.execute = (_e) }
> >                                   ^~
> >    cc1: some warnings being treated as errors
> >
> > vim +/asm_safe +3910 arch/x86/kvm/emulate.c
> >
> >   3904		rc = check_fxsr(ctxt);
> >   3905		if (rc != X86EMUL_CONTINUE)
> >   3906			return rc;
> >   3907	
> >   3908		ctxt->ops->get_fpu(ctxt);
> >   3909	
> > > 3910		rc = asm_safe("fxsave %[fx]", , [fx] "+m"(fx_state));
> >   3911	
> >   3912		ctxt->ops->put_fpu(ctxt);
> >   3913	
> >   3914		if (rc != X86EMUL_CONTINUE)
> >   3915			return rc;
> >   3916	
> >   3917		if (ctxt->ops->get_cr(ctxt, 4) & X86_CR4_OSFXSR)
> >   3918			size = offsetof(struct fxregs_state, xmm_space[8 * 16/4]);
> >   3919		else
> >   3920			size = offsetof(struct fxregs_state, xmm_space[0]);
> >   3921	
> >   3922		return segmented_write(ctxt, ctxt->memop.addr.mem, &fx_state, size);
> >   3923	}
> >   3924	
> >   3925	static int fxrstor_fixup(struct x86_emulate_ctxt *ctxt,
> >   3926			struct fxregs_state *new)
> >   3927	{
> >   3928		int rc = X86EMUL_CONTINUE;
> >   3929		struct fxregs_state old;
> >   3930	
> > > 3931		rc = asm_safe("fxsave %[fx]", , [fx] "+m"(old));
> >   3932		if (rc != X86EMUL_CONTINUE)
> >   3933			return rc;
> >   3934	
> >   3935		/*
> >   3936		 * 64 bit host will restore XMM 8-15, which is not correct on non-64
> >   3937		 * bit guests.  Load the current values in order to preserve 64 bit
> >   3938		 * XMMs after fxrstor.
> >   3939		 */
> >   3940	#ifdef CONFIG_X86_64
> >   3941		/* XXX: accessing XMM 8-15 very awkwardly */
> >   3942		memcpy(&new->xmm_space[8 * 16/4], &old.xmm_space[8 * 16/4], 8 * 16);
> >   3943	#endif
> >   3944	
> >   3945		/*
> >   3946		 * Hardware doesn't save and restore XMM 0-7 without CR4.OSFXSR, but
> >   3947		 * does save and restore MXCSR.
> >   3948		 */
> >   3949		if (!(ctxt->ops->get_cr(ctxt, 4) & X86_CR4_OSFXSR))
> >   3950			memcpy(new->xmm_space, old.xmm_space, 8 * 16);
> >   3951	
> >   3952		return rc;
> >   3953	}
> >   3954	
> >   3955	static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
> >   3956	{
> >   3957		struct fxregs_state fx_state;
> >   3958		int rc;
> >   3959	
> >   3960		rc = check_fxsr(ctxt);
> >   3961		if (rc != X86EMUL_CONTINUE)
> >   3962			return rc;
> >   3963	
> >   3964		rc = segmented_read(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
> >   3965		if (rc != X86EMUL_CONTINUE)
> >   3966			return rc;
> >   3967	
> >   3968		if (fx_state.mxcsr >> 16)
> >   3969			return emulate_gp(ctxt, 0);
> >   3970	
> >   3971		ctxt->ops->get_fpu(ctxt);
> >   3972	
> >   3973		if (ctxt->mode < X86EMUL_MODE_PROT64)
> >   3974			rc = fxrstor_fixup(ctxt, &fx_state);
> >   3975	
> >   3976		if (rc == X86EMUL_CONTINUE)
> > > 3977			rc = asm_safe("fxrstor %[fx]", : [fx] "m"(fx_state));
> >   3978	
> >   3979		ctxt->ops->put_fpu(ctxt);
> >   3980	
> >
> > ---
> > 0-DAY kernel test infrastructure                Open Source Technology Center
> > https://lists.01.org/pipermail/kbuild-all                   Intel Corporation