linux-kernel - Re: [PATCH 04/15] KVM: MMU: cache mmio info on page fault path

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 20 Jun 2011 13:14:32 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 04/15] KVM: MMU: cache mmio info on page fault path

On Tue, Jun 07, 2011 at 09:00:30PM +0800, Xiao Guangrong wrote:
> If the page fault is caused by mmio, we can cache the mmio info, later, we do
> not need to walk guest page table and quickly know it is a mmio fault while we
> emulate the mmio instruction
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> ---
>  arch/x86/include/asm/kvm_host.h |    5 +++
>  arch/x86/kvm/mmu.c              |   21 +++++----------
>  arch/x86/kvm/mmu.h              |   23 +++++++++++++++++
>  arch/x86/kvm/paging_tmpl.h      |   21 ++++++++++-----
>  arch/x86/kvm/x86.c              |   52 ++++++++++++++++++++++++++++++--------
>  arch/x86/kvm/x86.h              |   36 +++++++++++++++++++++++++++
>  6 files changed, 126 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index d167039..326af42 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -414,6 +414,11 @@ struct kvm_vcpu_arch {
>  	u64 mcg_ctl;
>  	u64 *mce_banks;
>  
> +	/* Cache MMIO info */
> +	u64 mmio_gva;
> +	unsigned access;
> +	gfn_t mmio_gfn;
> +
>  	/* used for guest single stepping over the given code position */
>  	unsigned long singlestep_rip;
>  

Why you're not implementing the original idea to cache the MMIO
attribute of an address into the spte?

That solution is wider reaching than a one-entry cache, and was proposed
to overcome large number of memslots.

If the access pattern switches between different addresses this one
solution is doomed.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/