linux-kernel - Re: [PATCH v8 1/6] KVM: x86: Consolidate flags for _

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Message-ID: <ZFtK/NS8rzCx9Mus@chao-email>
Date:   Wed, 10 May 2023 15:42:52 +0800
From:   Chao Gao <chao.gao@...el.com>
To:     Binbin Wu <binbin.wu@...ux.intel.com>
CC:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <seanjc@...gle.com>, <pbonzini@...hat.com>, <kai.huang@...el.com>,
        <robert.hu@...ux.intel.com>
Subject: Re: [PATCH v8 1/6] KVM: x86: Consolidate flags for __linearize()

On Wed, May 10, 2023 at 02:06:06PM +0800, Binbin Wu wrote:
>Define a 32-bit parameter and consolidate the two bools into it.
>
>__linearize() has two bool parameters write and fetch. And new flag
>will be needed to support new feature (e.g. LAM needs a flag to skip
>address untag under some conditions).
>
>No functional change intended.
>
>In the follow-up patches, the new parameter will be extended for LAM.
>
>Signed-off-by: Binbin Wu <binbin.wu@...ux.intel.com>

Reviewed-by: Chao Gao <chao.gao@...el.com>

one nit below

>---
> arch/x86/kvm/emulate.c     | 19 +++++++++++++------
> arch/x86/kvm/kvm_emulate.h |  4 ++++
> 2 files changed, 17 insertions(+), 6 deletions(-)
>
>diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>index 936a397a08cd..9508836e8a35 100644
>--- a/arch/x86/kvm/emulate.c
>+++ b/arch/x86/kvm/emulate.c
>@@ -687,8 +687,8 @@ static unsigned insn_alignment(struct x86_emulate_ctxt *ctxt, unsigned size)
> static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
> 				       struct segmented_address addr,
> 				       unsigned *max_size, unsigned size,
>-				       bool write, bool fetch,
>-				       enum x86emul_mode mode, ulong *linear)
>+				       u32 flags, enum x86emul_mode mode,
>+				       ulong *linear)
> {
> 	struct desc_struct desc;
> 	bool usable;
>@@ -696,6 +696,8 @@ static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
> 	u32 lim;
> 	u16 sel;
> 	u8  va_bits;
>+	bool fetch = !!(flags & X86EMUL_F_FETCH);
>+	bool write = !!(flags & X86EMUL_F_WRITE);
> 
> 	la = seg_base(ctxt, addr.seg) + addr.ea;
> 	*max_size = 0;
>@@ -757,7 +759,11 @@ static int linearize(struct x86_emulate_ctxt *ctxt,
> 		     ulong *linear)
> {
> 	unsigned max_size;
>-	return __linearize(ctxt, addr, &max_size, size, write, false,
>+	u32 flags = 0;
>+
>+	if (write)
>+		flags |= X86EMUL_F_WRITE;

this can be more dense:

	u32 flags = write ? X86EMUL_F_WRITE : 0;