From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH v2 8/8] kvm tools: Use brlock in MMIO and IOPORT
Date: Mon, 30 May 2011 10:47:59 +0200
Message-ID: <20110530084759.GI30513@elte.hu>
References: <1306744247-26051-1-git-send-email-levinsasha928@gmail.com>
 <1306744247-26051-8-git-send-email-levinsasha928@gmail.com>
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Cc: penberg@kernel.org, kvm@vger.kernel.org, asias.hejun@gmail.com,
	gorcunov@gmail.com, prasadjoshi124@gmail.com
To: Sasha Levin <levinsasha928@gmail.com>
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* Sasha Levin <levinsasha928@gmail.com> wrote:

> @@ -55,41 +56,53 @@ static const char *to_direction(u8 is_write)
>  bool kvm__register_mmio(u64 phys_addr, u64 phys_addr_len, void (*kvm_mmio_callback_fn)(u64 addr, u8 *data, u32 len, u8 is_write))
>  {
>  	struct mmio_mapping *mmio;
> +	int ret;
>  
>  	mmio = malloc(sizeof(*mmio));
>  	if (mmio == NULL)
>  		return false;
>  
> +	br_write_lock();
>  	*mmio = (struct mmio_mapping) {
>  		.node = RB_INT_INIT(phys_addr, phys_addr + phys_addr_len),
>  		.kvm_mmio_callback_fn = kvm_mmio_callback_fn,
>  	};

The initialization here does not use any global state AFAICS so it 
does not need the write lock, right?

>  
> -	return mmio_insert(&mmio_tree, mmio);
> +	ret = mmio_insert(&mmio_tree, mmio);
> +	br_write_unlock();

Shouldnt mmio_insert() thus have the write_lock()/unlock() sequence?

>  bool kvm__deregister_mmio(u64 phys_addr)
>  {
>  	struct mmio_mapping *mmio;
>  
> +	br_write_lock();
>  	mmio = mmio_search_single(&mmio_tree, phys_addr);
>  	if (mmio == NULL)
>  		return false;

Here we leak the write lock!

>  bool kvm__emulate_mmio(struct kvm *kvm, u64 phys_addr, u8 *data, u32 len, u8 is_write)
>  {
> -	struct mmio_mapping *mmio = mmio_search(&mmio_tree, phys_addr, len);
> +	struct mmio_mapping *mmio;
> +
> +	br_read_lock();
> +	mmio = mmio_search(&mmio_tree, phys_addr, len);
>  
>  	if (mmio)
>  		mmio->kvm_mmio_callback_fn(phys_addr, data, len, is_write);
>  	else
>  		fprintf(stderr, "Warning: Ignoring MMIO %s at %016llx (length %u)\n",
>  			to_direction(is_write), phys_addr, len);
> +	br_read_unlock();
>  
>  	return true;
>  }

Yummie, scalability here we come! :-)

Thanks,

	Ingo