Re: arch/powerpc/kvm/book3s_hv_nested.c:264:6: error: stack frame size of 2304 bytes in function 'kvmhv_enter_nested_guest'

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On 6/20/2021 4:59 PM, Nicholas Piggin wrote:
Excerpts from kernel test robot's message of April 3, 2021 8:47 pm:
tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   d93a0d43e3d0ba9e19387be4dae4a8d5b175a8d7
commit: 97e4910232fa1f81e806aa60c25a0450276d99a2 linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*
date:   3 weeks ago
config: powerpc64-randconfig-r006-20210403 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 0fe8af94688aa03c01913c2001d6a1a911f42ce6)
reproduce (this is a W=1 build):
         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
         chmod +x ~/bin/make.cross
         # install powerpc64 cross compiling tool for clang build
         # apt-get install binutils-powerpc64-linux-gnu
         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=97e4910232fa1f81e806aa60c25a0450276d99a2
         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
         git fetch --no-tags linus master
         git checkout 97e4910232fa1f81e806aa60c25a0450276d99a2
         # save the attached .config to linux build tree
         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc64

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All errors (new ones prefixed by >>):

arch/powerpc/kvm/book3s_hv_nested.c:264:6: error: stack frame size of 2304 bytes in function 'kvmhv_enter_nested_guest' [-Werror,-Wframe-larger-than=]
    long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
         ^
    1 error generated.


vim +/kvmhv_enter_nested_guest +264 arch/powerpc/kvm/book3s_hv_nested.c

Not much changed here recently. It's not that big a concern because it's
only called in the KVM ioctl path, not in any deep IO paths or anything,
and doesn't recurse. Might be a bit of inlining or stack spilling put it
over the edge.

It appears to be the fact that LLVM's PowerPC backend does not emit efficient byteswap assembly:

https://github.com/ClangBuiltLinux/linux/issues/1292

https://bugs.llvm.org/show_bug.cgi?id=49610

powerpc does make it an error though, would be good to avoid that so the
robot doesn't keep tripping over.

Marking byteswap_pt_regs as 'noinline_for_stack' drastically reduces the stack usage. If that is an acceptable solution, I can send it along tomorrow.

Cheers,
Nathan

Thanks,
Nick



afe75049303f75 Ravi Bangoria        2020-12-16  263
360cae313702cd Paul Mackerras       2018-10-08 @264  long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
360cae313702cd Paul Mackerras       2018-10-08  265  {
360cae313702cd Paul Mackerras       2018-10-08  266  	long int err, r;
360cae313702cd Paul Mackerras       2018-10-08  267  	struct kvm_nested_guest *l2;
360cae313702cd Paul Mackerras       2018-10-08  268  	struct pt_regs l2_regs, saved_l1_regs;
afe75049303f75 Ravi Bangoria        2020-12-16  269  	struct hv_guest_state l2_hv = {0}, saved_l1_hv;
360cae313702cd Paul Mackerras       2018-10-08  270  	struct kvmppc_vcore *vc = vcpu->arch.vcore;
360cae313702cd Paul Mackerras       2018-10-08  271  	u64 hv_ptr, regs_ptr;
360cae313702cd Paul Mackerras       2018-10-08  272  	u64 hdec_exp;
360cae313702cd Paul Mackerras       2018-10-08  273  	s64 delta_purr, delta_spurr, delta_ic, delta_vtb;
360cae313702cd Paul Mackerras       2018-10-08  274  	u64 mask;
360cae313702cd Paul Mackerras       2018-10-08  275  	unsigned long lpcr;
360cae313702cd Paul Mackerras       2018-10-08  276
360cae313702cd Paul Mackerras       2018-10-08  277  	if (vcpu->kvm->arch.l1_ptcr == 0)
360cae313702cd Paul Mackerras       2018-10-08  278  		return H_NOT_AVAILABLE;
360cae313702cd Paul Mackerras       2018-10-08  279
360cae313702cd Paul Mackerras       2018-10-08  280  	/* copy parameters in */
360cae313702cd Paul Mackerras       2018-10-08  281  	hv_ptr = kvmppc_get_gpr(vcpu, 4);
1508c22f112ce1 Alexey Kardashevskiy 2020-06-09  282  	regs_ptr = kvmppc_get_gpr(vcpu, 5);
1508c22f112ce1 Alexey Kardashevskiy 2020-06-09  283  	vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
afe75049303f75 Ravi Bangoria        2020-12-16  284  	err = kvmhv_read_guest_state_and_regs(vcpu, &l2_hv, &l2_regs,
afe75049303f75 Ravi Bangoria        2020-12-16  285  					      hv_ptr, regs_ptr);
1508c22f112ce1 Alexey Kardashevskiy 2020-06-09  286  	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
360cae313702cd Paul Mackerras       2018-10-08  287  	if (err)
360cae313702cd Paul Mackerras       2018-10-08  288  		return H_PARAMETER;
1508c22f112ce1 Alexey Kardashevskiy 2020-06-09  289
10b5022db7861a Suraj Jitindar Singh 2018-10-08  290  	if (kvmppc_need_byteswap(vcpu))
10b5022db7861a Suraj Jitindar Singh 2018-10-08  291  		byteswap_hv_regs(&l2_hv);
afe75049303f75 Ravi Bangoria        2020-12-16  292  	if (l2_hv.version > HV_GUEST_STATE_VERSION)
360cae313702cd Paul Mackerras       2018-10-08  293  		return H_P2;
360cae313702cd Paul Mackerras       2018-10-08  294
10b5022db7861a Suraj Jitindar Singh 2018-10-08  295  	if (kvmppc_need_byteswap(vcpu))
10b5022db7861a Suraj Jitindar Singh 2018-10-08  296  		byteswap_pt_regs(&l2_regs);
9d0b048da788c1 Suraj Jitindar Singh 2018-10-08  297  	if (l2_hv.vcpu_token >= NR_CPUS)
9d0b048da788c1 Suraj Jitindar Singh 2018-10-08  298  		return H_PARAMETER;
9d0b048da788c1 Suraj Jitindar Singh 2018-10-08  299
360cae313702cd Paul Mackerras       2018-10-08  300  	/* translate lpid */
360cae313702cd Paul Mackerras       2018-10-08  301  	l2 = kvmhv_get_nested(vcpu->kvm, l2_hv.lpid, true);
360cae313702cd Paul Mackerras       2018-10-08  302  	if (!l2)
360cae313702cd Paul Mackerras       2018-10-08  303  		return H_PARAMETER;
360cae313702cd Paul Mackerras       2018-10-08  304  	if (!l2->l1_gr_to_hr) {
360cae313702cd Paul Mackerras       2018-10-08  305  		mutex_lock(&l2->tlb_lock);
360cae313702cd Paul Mackerras       2018-10-08  306  		kvmhv_update_ptbl_cache(l2);
360cae313702cd Paul Mackerras       2018-10-08  307  		mutex_unlock(&l2->tlb_lock);
360cae313702cd Paul Mackerras       2018-10-08  308  	}
360cae313702cd Paul Mackerras       2018-10-08  309
360cae313702cd Paul Mackerras       2018-10-08  310  	/* save l1 values of things */
360cae313702cd Paul Mackerras       2018-10-08  311  	vcpu->arch.regs.msr = vcpu->arch.shregs.msr;
360cae313702cd Paul Mackerras       2018-10-08  312  	saved_l1_regs = vcpu->arch.regs;
360cae313702cd Paul Mackerras       2018-10-08  313  	kvmhv_save_hv_regs(vcpu, &saved_l1_hv);
360cae313702cd Paul Mackerras       2018-10-08  314
360cae313702cd Paul Mackerras       2018-10-08  315  	/* convert TB values/offsets to host (L0) values */
360cae313702cd Paul Mackerras       2018-10-08  316  	hdec_exp = l2_hv.hdec_expiry - vc->tb_offset;
360cae313702cd Paul Mackerras       2018-10-08  317  	vc->tb_offset += l2_hv.tb_offset;
360cae313702cd Paul Mackerras       2018-10-08  318
360cae313702cd Paul Mackerras       2018-10-08  319  	/* set L1 state to L2 state */
360cae313702cd Paul Mackerras       2018-10-08  320  	vcpu->arch.nested = l2;
360cae313702cd Paul Mackerras       2018-10-08  321  	vcpu->arch.nested_vcpu_id = l2_hv.vcpu_token;
360cae313702cd Paul Mackerras       2018-10-08  322  	vcpu->arch.regs = l2_regs;
360cae313702cd Paul Mackerras       2018-10-08  323  	vcpu->arch.shregs.msr = vcpu->arch.regs.msr;
360cae313702cd Paul Mackerras       2018-10-08  324  	mask = LPCR_DPFD | LPCR_ILE | LPCR_TC | LPCR_AIL | LPCR_LD |
360cae313702cd Paul Mackerras       2018-10-08  325  		LPCR_LPES | LPCR_MER;
360cae313702cd Paul Mackerras       2018-10-08  326  	lpcr = (vc->lpcr & ~mask) | (l2_hv.lpcr & mask);
73937deb4b2d7f Suraj Jitindar Singh 2018-10-08  327  	sanitise_hv_regs(vcpu, &l2_hv);
360cae313702cd Paul Mackerras       2018-10-08  328  	restore_hv_regs(vcpu, &l2_hv);
360cae313702cd Paul Mackerras       2018-10-08  329
360cae313702cd Paul Mackerras       2018-10-08  330  	vcpu->arch.ret = RESUME_GUEST;
360cae313702cd Paul Mackerras       2018-10-08  331  	vcpu->arch.trap = 0;
360cae313702cd Paul Mackerras       2018-10-08  332  	do {
360cae313702cd Paul Mackerras       2018-10-08  333  		if (mftb() >= hdec_exp) {
360cae313702cd Paul Mackerras       2018-10-08  334  			vcpu->arch.trap = BOOK3S_INTERRUPT_HV_DECREMENTER;
360cae313702cd Paul Mackerras       2018-10-08  335  			r = RESUME_HOST;
360cae313702cd Paul Mackerras       2018-10-08  336  			break;
360cae313702cd Paul Mackerras       2018-10-08  337  		}
8c99d34578628b Tianjia Zhang        2020-04-27  338  		r = kvmhv_run_single_vcpu(vcpu, hdec_exp, lpcr);
360cae313702cd Paul Mackerras       2018-10-08  339  	} while (is_kvmppc_resume_guest(r));
360cae313702cd Paul Mackerras       2018-10-08  340
360cae313702cd Paul Mackerras       2018-10-08  341  	/* save L2 state for return */
360cae313702cd Paul Mackerras       2018-10-08  342  	l2_regs = vcpu->arch.regs;
360cae313702cd Paul Mackerras       2018-10-08  343  	l2_regs.msr = vcpu->arch.shregs.msr;
360cae313702cd Paul Mackerras       2018-10-08  344  	delta_purr = vcpu->arch.purr - l2_hv.purr;
360cae313702cd Paul Mackerras       2018-10-08  345  	delta_spurr = vcpu->arch.spurr - l2_hv.spurr;
360cae313702cd Paul Mackerras       2018-10-08  346  	delta_ic = vcpu->arch.ic - l2_hv.ic;
360cae313702cd Paul Mackerras       2018-10-08  347  	delta_vtb = vc->vtb - l2_hv.vtb;
360cae313702cd Paul Mackerras       2018-10-08  348  	save_hv_return_state(vcpu, vcpu->arch.trap, &l2_hv);
360cae313702cd Paul Mackerras       2018-10-08  349
360cae313702cd Paul Mackerras       2018-10-08  350  	/* restore L1 state */
360cae313702cd Paul Mackerras       2018-10-08  351  	vcpu->arch.nested = NULL;
360cae313702cd Paul Mackerras       2018-10-08  352  	vcpu->arch.regs = saved_l1_regs;
360cae313702cd Paul Mackerras       2018-10-08  353  	vcpu->arch.shregs.msr = saved_l1_regs.msr & ~MSR_TS_MASK;
360cae313702cd Paul Mackerras       2018-10-08  354  	/* set L1 MSR TS field according to L2 transaction state */
360cae313702cd Paul Mackerras       2018-10-08  355  	if (l2_regs.msr & MSR_TS_MASK)
360cae313702cd Paul Mackerras       2018-10-08  356  		vcpu->arch.shregs.msr |= MSR_TS_S;
360cae313702cd Paul Mackerras       2018-10-08  357  	vc->tb_offset = saved_l1_hv.tb_offset;
360cae313702cd Paul Mackerras       2018-10-08  358  	restore_hv_regs(vcpu, &saved_l1_hv);
360cae313702cd Paul Mackerras       2018-10-08  359  	vcpu->arch.purr += delta_purr;
360cae313702cd Paul Mackerras       2018-10-08  360  	vcpu->arch.spurr += delta_spurr;
360cae313702cd Paul Mackerras       2018-10-08  361  	vcpu->arch.ic += delta_ic;
360cae313702cd Paul Mackerras       2018-10-08  362  	vc->vtb += delta_vtb;
360cae313702cd Paul Mackerras       2018-10-08  363
360cae313702cd Paul Mackerras       2018-10-08  364  	kvmhv_put_nested(l2);
360cae313702cd Paul Mackerras       2018-10-08  365
360cae313702cd Paul Mackerras       2018-10-08  366  	/* copy l2_hv_state and regs back to guest */
10b5022db7861a Suraj Jitindar Singh 2018-10-08  367  	if (kvmppc_need_byteswap(vcpu)) {
10b5022db7861a Suraj Jitindar Singh 2018-10-08  368  		byteswap_hv_regs(&l2_hv);
10b5022db7861a Suraj Jitindar Singh 2018-10-08  369  		byteswap_pt_regs(&l2_regs);
10b5022db7861a Suraj Jitindar Singh 2018-10-08  370  	}
1508c22f112ce1 Alexey Kardashevskiy 2020-06-09  371  	vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
afe75049303f75 Ravi Bangoria        2020-12-16  372  	err = kvmhv_write_guest_state_and_regs(vcpu, &l2_hv, &l2_regs,
afe75049303f75 Ravi Bangoria        2020-12-16  373  					       hv_ptr, regs_ptr);
1508c22f112ce1 Alexey Kardashevskiy 2020-06-09  374  	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
360cae313702cd Paul Mackerras       2018-10-08  375  	if (err)
360cae313702cd Paul Mackerras       2018-10-08  376  		return H_AUTHORITY;
360cae313702cd Paul Mackerras       2018-10-08  377
360cae313702cd Paul Mackerras       2018-10-08  378  	if (r == -EINTR)
360cae313702cd Paul Mackerras       2018-10-08  379  		return H_INTERRUPT;
360cae313702cd Paul Mackerras       2018-10-08  380
873db2cd9a6d7f Suraj Jitindar Singh 2018-12-14  381  	if (vcpu->mmio_needed) {
873db2cd9a6d7f Suraj Jitindar Singh 2018-12-14  382  		kvmhv_nested_mmio_needed(vcpu, regs_ptr);
873db2cd9a6d7f Suraj Jitindar Singh 2018-12-14  383  		return H_TOO_HARD;
873db2cd9a6d7f Suraj Jitindar Singh 2018-12-14  384  	}
873db2cd9a6d7f Suraj Jitindar Singh 2018-12-14  385
360cae313702cd Paul Mackerras       2018-10-08  386  	return vcpu->arch.trap;
360cae313702cd Paul Mackerras       2018-10-08  387  }
360cae313702cd Paul Mackerras       2018-10-08  388

:::::: The code at line 264 was first introduced by commit
:::::: 360cae313702cdd0b90f82c261a8302fecef030a KVM: PPC: Book3S HV: Nested guest entry via hypercall

:::::: TO: Paul Mackerras <paulus@xxxxxxxxxx>
:::::: CC: Michael Ellerman <mpe@xxxxxxxxxxxxxx>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx




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