linux-kernel - Re: [PATCH 3/4] KVM: SVM: Add GHCB Accessor functions

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Date:   Thu, 30 Jul 2020 15:05:31 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 3/4] KVM: SVM: Add GHCB Accessor functions

On Wed, Jul 29, 2020 at 08:43:28AM -0700, Sean Christopherson wrote:
> Rather than manually calculate the byte/bit indices just use __set_bit()
> and test_bit().  That will also solve the variable declaration issue.
> 
> E.g.
> 
> #define GHB_BITMAP_IDX(field)		\
> 	(offsetof(struct vmcb_save_area, (field)) / sizeof(u64))
> 
> #define GHCB_SET_VALID(ghcb, field)	\
> 	__set_bit(GHCB_BITMAP_IDX(field), (unsigned long *)&ghcb->save.valid_bitmap)
> 
> Or alternatively drop GHCB_SET_VALID() and just open code the two users.

Thanks for your suggestions, I updated the patch and will do some
testing before re-posting.

Regards,

	Joerg

> 
> > +	}
> > +
> > +#define DEFINE_GHCB_SETTER(field)					\
> > +	static inline void						\
> > +	ghcb_set_##field(struct ghcb *ghcb, u64 value)			\
> > +	{								\
> > +		GHCB_SET_VALID(ghcb, field)				\
> > +		(ghcb)->save.field = value;				\
> 
> 
> The ghcb doesn't need to be wrapped in (), it's a parameter to a function.
> Same comment for the below usage.
> 
> > +	}
> > +
> > +#define DEFINE_GHCB_ACCESSORS(field)					\
> > +	static inline bool ghcb_is_valid_##field(const struct ghcb *ghcb)	\
> 
> I'd prefer to follow the naming of the arch reg accessors, i.e.
> 
> 	static inline bool ghcb_##field##_is_valid(...)
> 
> to pair with
> 
> 	kvm_##lname##_read
> 	kvm_##lname##_write
> 
> And because ghcb_is_valid_rip() reads a bit weird, e.g. IMO is more likely
> to be read as "does the RIP in the GHCB hold a valid (canonical) value",
> versus ghcb_rip_is_valid() reading as "is RIP valid in the GHCB".
> 
> > +	{								\
> > +		DEFINE_GHCB_INDICES(field)				\
> > +		return !!((ghcb)->save.valid_bitmap[byte_idx]		\
> > +						& BIT(bit_idx));	\
> > +	}								\
> > +									\
> > +	static inline void						\
> > +	ghcb_set_##field(struct ghcb *ghcb, u64 value)			\
> > +	{								\
> > +		GHCB_SET_VALID(ghcb, field)				\
> > +		(ghcb)->save.field = value;				\
> 
> > +	}
> > +
> > +DEFINE_GHCB_ACCESSORS(cpl)
> > +DEFINE_GHCB_ACCESSORS(rip)
> > +DEFINE_GHCB_ACCESSORS(rsp)
> > +DEFINE_GHCB_ACCESSORS(rax)
> > +DEFINE_GHCB_ACCESSORS(rcx)
> > +DEFINE_GHCB_ACCESSORS(rdx)
> > +DEFINE_GHCB_ACCESSORS(rbx)
> > +DEFINE_GHCB_ACCESSORS(rbp)
> > +DEFINE_GHCB_ACCESSORS(rsi)
> > +DEFINE_GHCB_ACCESSORS(rdi)
> > +DEFINE_GHCB_ACCESSORS(r8)
> > +DEFINE_GHCB_ACCESSORS(r9)
> > +DEFINE_GHCB_ACCESSORS(r10)
> > +DEFINE_GHCB_ACCESSORS(r11)
> > +DEFINE_GHCB_ACCESSORS(r12)
> > +DEFINE_GHCB_ACCESSORS(r13)
> > +DEFINE_GHCB_ACCESSORS(r14)
> > +DEFINE_GHCB_ACCESSORS(r15)
> > +DEFINE_GHCB_ACCESSORS(sw_exit_code)
> > +DEFINE_GHCB_ACCESSORS(sw_exit_info_1)
> > +DEFINE_GHCB_ACCESSORS(sw_exit_info_2)
> > +DEFINE_GHCB_ACCESSORS(sw_scratch)
> > +DEFINE_GHCB_ACCESSORS(xcr0)
> > +
> >  #endif
> > -- 
> > 2.17.1
> >