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

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Message-ID: <68a5df32-82de-1f07-5ea2-52ecf1c17e63@linux.intel.com>
Date:   Thu, 11 May 2023 09:25:42 +0800
From:   Binbin Wu <binbin.wu@...ux.intel.com>
To:     Chao Gao <chao.gao@...el.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 5/10/2023 3:42 PM, Chao Gao wrote:
> 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;
Thanks, will update it.