From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B96FF223702; Tue, 24 Feb 2026 20:54:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771966458; cv=none; b=UrnWBL1gfcFxHD4yBnnAz/tsqFruYyYCYy8arFGsY8udGfjxr1VZhY0iDfZ97FT3az4J4UK5UYG3N95hhOBzMCvklGZFO9SYeOa4qHGJsboR9RPZDPDFo6qvlOLp2llmWX1PMeKzfMWkhbj9fyw06/PfDZcUgRfphNmbtvtNbH4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771966458; c=relaxed/simple; bh=EgVAY0e5tBoSz6A6iwW5/XO8EvjgmD/hBAtfckjnAIc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=DYAnzz9U5FxQuc4Rqy2FvOFxvDucL3f8KD4suueeBHMUNoT65/1L3p18QpxlaZMypcuRRyPHwTUsrxUXeKJnCEucpZ+X/dqjB2S4vz9bSufpCdTNTepXugqXrWhR4ZqvrCff0tOy71HcYw/OboNreJlLI4JJdDQ4QZ89hfRDxBM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fU9VoxpY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fU9VoxpY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 279EDC116D0; Tue, 24 Feb 2026 20:54:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771966458; bh=EgVAY0e5tBoSz6A6iwW5/XO8EvjgmD/hBAtfckjnAIc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fU9VoxpYqnAVrd4t/fIENYWIsMId2KNEP3dfw2h4SjQzeH/MBV/5Cee/wntRTQCP6 8EADR9JKKOK/hSexd/fEomD/ZrU3e+Mo0cAkKAlisOPYRwuKJXzT3MA26tdQTXMvpb cFKvEXyKAe/X10m3pmNX2H1z0cczPw3iZWdEsiJJoujd4S5bnLIF7pTBSYnWQRgIVb lO1qmLmIs5NJLzUq5pV5qVfuG1vDdgGb4JylPzxBqN/lvS2sL0Y7jYkwDaBcxLLsMY M8xREJGMjxcu5uVJY3DLJp8/BXSitkrqLBWUKwurl88mBMEyWsx/eqM0TQ42RGOP4K O37lVNZp675Mw== Date: Tue, 24 Feb 2026 12:54:16 -0800 From: Oliver Upton To: Yeoreum Yun Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, maz@kernel.org, miko.lenczewski@arm.com, kevin.brodsky@arm.com, broonie@kernel.org, ardb@kernel.org, suzuki.poulose@arm.com, lpieralisi@kernel.org, yangyicong@hisilicon.com, joey.gouly@arm.com, yuzenghui@huawei.com Subject: Re: [PATCH v13 7/8] KVM: arm64: use CASLT instruction for swapping guest descriptor Message-ID: References: <20260223174802.458411-1-yeoreum.yun@arm.com> <20260223174802.458411-8-yeoreum.yun@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260223174802.458411-8-yeoreum.yun@arm.com> On Mon, Feb 23, 2026 at 05:48:01PM +0000, Yeoreum Yun wrote: > Use the CASLT instruction to swap the guest descriptor when FEAT_LSUI > is enabled, avoiding the need to clear the PAN bit. > > Signed-off-by: Yeoreum Yun > --- > arch/arm64/include/asm/futex.h | 17 +---------------- > arch/arm64/include/asm/lsui.h | 27 +++++++++++++++++++++++++++ > arch/arm64/kvm/at.c | 32 +++++++++++++++++++++++++++++++- > 3 files changed, 59 insertions(+), 17 deletions(-) > create mode 100644 arch/arm64/include/asm/lsui.h > > diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h > index b579e9d0964d..6779c4ad927f 100644 > --- a/arch/arm64/include/asm/futex.h > +++ b/arch/arm64/include/asm/futex.h > @@ -7,11 +7,9 @@ > > #include > #include > -#include > > -#include > -#include > #include > +#include > > #define FUTEX_MAX_LOOPS 128 /* What's the largest number you can think of? */ > > @@ -91,8 +89,6 @@ __llsc_futex_cmpxchg(u32 __user *uaddr, u32 oldval, u32 newval, u32 *oval) > > #ifdef CONFIG_ARM64_LSUI > > -#define __LSUI_PREAMBLE ".arch_extension lsui\n" > - > #define LSUI_FUTEX_ATOMIC_OP(op, asm_op) \ > static __always_inline int \ > __lsui_futex_atomic_##op(int oparg, u32 __user *uaddr, int *oval) \ > @@ -235,17 +231,6 @@ __lsui_futex_cmpxchg(u32 __user *uaddr, u32 oldval, u32 newval, u32 *oval) > { > return __lsui_cmpxchg32(uaddr, oldval, newval, oval); > } > - > -#define __lsui_llsc_body(op, ...) \ > -({ \ > - alternative_has_cap_unlikely(ARM64_HAS_LSUI) ? \ > - __lsui_##op(__VA_ARGS__) : __llsc_##op(__VA_ARGS__); \ > -}) > - > -#else /* CONFIG_ARM64_LSUI */ > - > -#define __lsui_llsc_body(op, ...) __llsc_##op(__VA_ARGS__) > - > #endif /* CONFIG_ARM64_LSUI */ > > > diff --git a/arch/arm64/include/asm/lsui.h b/arch/arm64/include/asm/lsui.h > new file mode 100644 > index 000000000000..4f956188835e > --- /dev/null > +++ b/arch/arm64/include/asm/lsui.h > @@ -0,0 +1,27 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ASM_LSUI_H > +#define __ASM_LSUI_H > + > +#include > +#include > +#include > +#include > +#include > + > +#ifdef CONFIG_ARM64_LSUI > + > +#define __LSUI_PREAMBLE ".arch_extension lsui\n" > + > +#define __lsui_llsc_body(op, ...) \ > +({ \ > + alternative_has_cap_unlikely(ARM64_HAS_LSUI) ? \ > + __lsui_##op(__VA_ARGS__) : __llsc_##op(__VA_ARGS__); \ > +}) > + > +#else /* CONFIG_ARM64_LSUI */ > + > +#define __lsui_llsc_body(op, ...) __llsc_##op(__VA_ARGS__) > + > +#endif /* CONFIG_ARM64_LSUI */ > + > +#endif /* __ASM_LSUI_H */ > diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c > index 885bd5bb2f41..1aceeef04567 100644 > --- a/arch/arm64/kvm/at.c > +++ b/arch/arm64/kvm/at.c > @@ -9,6 +9,7 @@ > #include > #include > #include > +#include > > static void fail_s1_walk(struct s1_walk_result *wr, u8 fst, bool s1ptw) > { > @@ -1704,6 +1705,33 @@ int __kvm_find_s1_desc_level(struct kvm_vcpu *vcpu, u64 va, u64 ipa, int *level) > } > } > > +#ifdef CONFIG_ARM64_LSUI > +static int __lsui_swap_desc(u64 __user *ptep, u64 old, u64 new) > +{ > + u64 tmp = old; > + int ret = 0; > + > + uaccess_ttbr0_enable(); > + > + asm volatile(__LSUI_PREAMBLE > + "1: caslt %[old], %[new], %[addr]\n" > + "2:\n" > + _ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w[ret]) > + : [old] "+r" (old), [addr] "+Q" (*ptep), [ret] "+r" (ret) > + : [new] "r" (new) > + : "memory"); > + > + uaccess_ttbr0_disable(); > + > + if (ret) > + return ret; > + if (tmp != old) > + return -EAGAIN; > + > + return ret; > +} > +#endif > + > static int __lse_swap_desc(u64 __user *ptep, u64 old, u64 new) > { > u64 tmp = old; > @@ -1779,7 +1807,9 @@ int __kvm_at_swap_desc(struct kvm *kvm, gpa_t ipa, u64 old, u64 new) > return -EPERM; > > ptep = (u64 __user *)hva + offset; > - if (cpus_have_final_cap(ARM64_HAS_LSE_ATOMICS)) > + if (IS_ENABLED(CONFIG_ARM64_LSUI) && cpus_have_final_cap(ARM64_HAS_LSUI)) cpucap_is_possible() is where the Kconfig check should go. Thanks, Oliver