linux-kernel - Re: [PATCH 1/3] KVM: MTRR: fix memory type handling if MTRR is completely disabled

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Date:	Wed, 15 Jul 2015 22:10:18 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
Cc:	pbonzini@...hat.com, gleb@...nel.org, mtosatti@...hat.com,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, bsd@...hat.com,
	lersek@...hat.com, jordan.l.justen@...el.com,
	edk2-devel@...ts.sourceforge.net,
	Xiao Guangrong <guangrong.xiao@...el.com>
Subject: Re: [PATCH 1/3] KVM: MTRR: fix memory type handling if MTRR is
 completely disabled

On Thu, 2015-07-16 at 03:25 +0800, Xiao Guangrong wrote:
> From: Xiao Guangrong <guangrong.xiao@...el.com>
> 
> Currently code uses default memory type if MTRR is fully disabled,
> fix it by using UC instead
> 
> Signed-off-by: Xiao Guangrong <guangrong.xiao@...el.com>
> ---

Seems to work for me.  I don't see a 0th patch, but for the series:

Tested-by: Alex Williamson <alex.williamson@...hat.com>

Thanks!

>  arch/x86/kvm/mtrr.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
> index de1d2d8..e275013 100644
> --- a/arch/x86/kvm/mtrr.c
> +++ b/arch/x86/kvm/mtrr.c
> @@ -120,6 +120,16 @@ static u8 mtrr_default_type(struct kvm_mtrr *mtrr_state)
>  	return mtrr_state->deftype & IA32_MTRR_DEF_TYPE_TYPE_MASK;
>  }
>  
> +static u8 mtrr_disabled_type(void)
> +{
> +	/*
> +	 * Intel SDM 11.11.2.2: all MTRRs are disabled when
> +	 * IA32_MTRR_DEF_TYPE.E bit is cleared, and the UC
> +	 * memory type is applied to all of physical memory.
> +	 */
> +	return MTRR_TYPE_UNCACHABLE;
> +}
> +
>  /*
>  * Three terms are used in the following code:
>  * - segment, it indicates the address segments covered by fixed MTRRs.
> @@ -434,6 +444,8 @@ struct mtrr_iter {
>  
>  	/* output fields. */
>  	int mem_type;
> +	/* mtrr is completely disabled? */
> +	bool mtrr_disabled;
>  	/* [start, end) is not fully covered in MTRRs? */
>  	bool partial_map;
>  
> @@ -549,7 +561,7 @@ static void mtrr_lookup_var_next(struct mtrr_iter *iter)
>  static void mtrr_lookup_start(struct mtrr_iter *iter)
>  {
>  	if (!mtrr_is_enabled(iter->mtrr_state)) {
> -		iter->partial_map = true;
> +		iter->mtrr_disabled = true;
>  		return;
>  	}
>  
> @@ -563,6 +575,7 @@ static void mtrr_lookup_init(struct mtrr_iter *iter,
>  	iter->mtrr_state = mtrr_state;
>  	iter->start = start;
>  	iter->end = end;
> +	iter->mtrr_disabled = false;
>  	iter->partial_map = false;
>  	iter->fixed = false;
>  	iter->range = NULL;
> @@ -656,6 +669,9 @@ u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
>  		return MTRR_TYPE_WRBACK;
>  	}
>  
> +	if (iter.mtrr_disabled)
> +		return mtrr_disabled_type();
> +
>  	/* It is not covered by MTRRs. */
>  	if (iter.partial_map) {
>  		/*
> @@ -689,6 +705,9 @@ bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
>  			return false;
>  	}
>  
> +	if (iter.mtrr_disabled)
> +		return true;
> +
>  	if (!iter.partial_map)
>  		return true;
>  



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