summaryrefslogtreecommitdiff
path: root/arch
diff options
context:
space:
mode:
authorNathan Chancellor <nathan@kernel.org>2021-06-21 11:24:40 -0700
committerMichael Ellerman <mpe@ellerman.id.au>2021-06-23 00:18:30 +1000
commit51696f39cbee5bb684e7959c0c98b5f54548aa34 (patch)
treec2b3e5590fbda46b0e951189c1929ce9afc9e0be /arch
parent81468083f3c76a08183813e3af63a7c3cea3f537 (diff)
KVM: PPC: Book3S HV: Workaround high stack usage with clang
LLVM does not emit optimal byteswap assembly, which results in high stack usage in kvmhv_enter_nested_guest() due to the inlining of byteswap_pt_regs(). With LLVM 12.0.0: arch/powerpc/kvm/book3s_hv_nested.c:289:6: error: stack frame size of 2512 bytes in function 'kvmhv_enter_nested_guest' [-Werror,-Wframe-larger-than=] long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu) ^ 1 error generated. While this gets fixed in LLVM, mark byteswap_pt_regs() as noinline_for_stack so that it does not get inlined and break the build due to -Werror by default in arch/powerpc/. Not inlining saves approximately 800 bytes with LLVM 12.0.0: arch/powerpc/kvm/book3s_hv_nested.c:290:6: warning: stack frame size of 1728 bytes in function 'kvmhv_enter_nested_guest' [-Wframe-larger-than=] long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu) ^ 1 warning generated. Cc: stable@vger.kernel.org # v4.20+ Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://github.com/ClangBuiltLinux/linux/issues/1292 Link: https://bugs.llvm.org/show_bug.cgi?id=49610 Link: https://lore.kernel.org/r/202104031853.vDT0Qjqj-lkp@intel.com/ Link: https://gist.github.com/ba710e3703bf45043a31e2806c843ffd Link: https://lore.kernel.org/r/20210621182440.990242-1-nathan@kernel.org
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kvm/book3s_hv_nested.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index 3a06ac0b53e2..8543ad538b0c 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -54,7 +54,8 @@ void kvmhv_save_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr)
hr->dawrx1 = vcpu->arch.dawrx1;
}
-static void byteswap_pt_regs(struct pt_regs *regs)
+/* Use noinline_for_stack due to https://bugs.llvm.org/show_bug.cgi?id=49610 */
+static noinline_for_stack void byteswap_pt_regs(struct pt_regs *regs)
{
unsigned long *addr = (unsigned long *) regs;