From: Sean Christopherson <seanjc@google.com>
To: Uros Bizjak <ubizjak@gmail.com>
Cc: kvm@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 1/2] KVM: x86: Use asm_inline() instead of asm() in kvm_hypercall[0-4]()
Date: Mon, 14 Apr 2025 18:04:53 -0700 [thread overview]
Message-ID: <Z_2wtfAAxb5uNP4g@google.com> (raw)
In-Reply-To: <20250414081131.97374-1-ubizjak@gmail.com>
Nit, this is guest code, i.e. should use "kvm/x86:" for the scope. No need to
send a new version just for that.
On Mon, Apr 14, 2025, Uros Bizjak wrote:
> Use asm_inline() to instruct the compiler that the size of asm()
> is the minimum size of one instruction, ignoring how many instructions
> the compiler thinks it is. ALTERNATIVE macro that expands to several
> pseudo directives causes instruction length estimate to count
> more than 20 instructions.
>
> bloat-o-meter reports minimal code size increase
> (x86_64 defconfig, gcc-14.2.1):
>
> add/remove: 0/0 grow/shrink: 1/0 up/down: 10/0 (10)
>
> Function old new delta
> -----------------------------------------------------
> __send_ipi_mask 525 535 +10
>
> Total: Before=23751224, After=23751234, chg +0.00%
>
> due to different compiler decisions with more precise size
> estimations.
>
> No functional change intended.
>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> ---
> arch/x86/include/asm/kvm_para.h | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
> index 57bc74e112f2..519ab5aee250 100644
> --- a/arch/x86/include/asm/kvm_para.h
> +++ b/arch/x86/include/asm/kvm_para.h
> @@ -38,7 +38,7 @@ static inline long kvm_hypercall0(unsigned int nr)
> if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> return tdx_kvm_hypercall(nr, 0, 0, 0, 0);
>
> - asm volatile(KVM_HYPERCALL
> + asm_inline volatile(KVM_HYPERCALL
> : "=a"(ret)
> : "a"(nr)
> : "memory");
> @@ -52,7 +52,7 @@ static inline long kvm_hypercall1(unsigned int nr, unsigned long p1)
> if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> return tdx_kvm_hypercall(nr, p1, 0, 0, 0);
>
> - asm volatile(KVM_HYPERCALL
> + asm_inline volatile(KVM_HYPERCALL
> : "=a"(ret)
> : "a"(nr), "b"(p1)
> : "memory");
> @@ -67,7 +67,7 @@ static inline long kvm_hypercall2(unsigned int nr, unsigned long p1,
> if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> return tdx_kvm_hypercall(nr, p1, p2, 0, 0);
>
> - asm volatile(KVM_HYPERCALL
> + asm_inline volatile(KVM_HYPERCALL
> : "=a"(ret)
> : "a"(nr), "b"(p1), "c"(p2)
> : "memory");
> @@ -82,7 +82,7 @@ static inline long kvm_hypercall3(unsigned int nr, unsigned long p1,
> if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> return tdx_kvm_hypercall(nr, p1, p2, p3, 0);
>
> - asm volatile(KVM_HYPERCALL
> + asm_inline volatile(KVM_HYPERCALL
> : "=a"(ret)
> : "a"(nr), "b"(p1), "c"(p2), "d"(p3)
> : "memory");
> @@ -98,7 +98,7 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1,
> if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> return tdx_kvm_hypercall(nr, p1, p2, p3, p4);
>
> - asm volatile(KVM_HYPERCALL
> + asm_inline volatile(KVM_HYPERCALL
> : "=a"(ret)
> : "a"(nr), "b"(p1), "c"(p2), "d"(p3), "S"(p4)
> : "memory");
> --
> 2.49.0
>
next prev parent reply other threads:[~2025-04-15 1:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-14 8:10 [PATCH 1/2] KVM: x86: Use asm_inline() instead of asm() in kvm_hypercall[0-4]() Uros Bizjak
2025-04-14 8:10 ` [PATCH 2/2] KVM: VMX: Use LEAVE in vmx_do_interrupt_irqoff() Uros Bizjak
2025-04-15 1:05 ` Sean Christopherson
2025-04-15 7:42 ` Uros Bizjak
2025-04-15 1:04 ` Sean Christopherson [this message]
2025-04-25 23:23 ` [PATCH 1/2] KVM: x86: Use asm_inline() instead of asm() in kvm_hypercall[0-4]() Sean Christopherson
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