linux-kernel - Re: [PATCH] KVM: PPC: Book3S HV: Workaround high stack usage with clang

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Date:   Thu, 24 Jun 2021 23:59:16 +1000
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Paul Mackerras <paulus@...abs.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nathan Chancellor <nathan@...nel.org>
Cc:     kernel test robot <lkp@...el.com>,
        Nicholas Piggin <npiggin@...il.com>,
        clang-built-linux@...glegroups.com, kvm-ppc@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] KVM: PPC: Book3S HV: Workaround high stack usage with clang

On Mon, 21 Jun 2021 11:24:40 -0700, Nathan Chancellor wrote:
> 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.
> 
> [...]

Applied to powerpc/topic/ppc-kvm.

[1/1] KVM: PPC: Book3S HV: Workaround high stack usage with clang
      https://git.kernel.org/powerpc/c/51696f39cbee5bb684e7959c0c98b5f54548aa34

cheers