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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>,
	xen-devel <xen-devel@lists.xenproject.org>
Cc: Paul Durrant <paul.durrant@citrix.com>
Subject: Re: [PATCH 1/2] x86/HVM: latch linear->phys translation results
Date: Thu, 9 Jun 2016 12:54:54 +0100	[thread overview]
Message-ID: <5759590E.80907@citrix.com> (raw)
In-Reply-To: <5758353702000078000F30FA@prv-mh.provo.novell.com>

On 08/06/16 14:09, Jan Beulich wrote:
> ... to avoid re-doing the same translation later again (in a retry, for
> example). This doesn't help very often according to my testing, but
> it's pretty cheap to have, and will be of further use subsequently.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -678,6 +678,19 @@ static struct hvm_mmio_cache *hvmemul_fi
>      return cache;
>  }
>  
> +static void latch_linear_to_phys(struct hvm_vcpu_io *vio, unsigned long gla,
> +                                 unsigned long gpa, bool_t write)
> +{
> +    if ( vio->mmio_access.gla_valid )
> +        return;
> +
> +    vio->mmio_gva = gla & PAGE_MASK;

This suggest that mmio_vga is mis-named.

Looking at the uses, handle_mmio_with_translation() is used
inconsistently, with virtual addresses from the shadow code, but linear
addresses from nested hap code.

Clearly one of these two users are buggy for guests running in a non
flat way, and it looks to be the shadow side which is buggy.


Following my recent fun with invlpg handling, I am much more conscious
about the distinction between virtual and linear addresses.  I wonder if
we want to go so far as to have a TYPE_SAFE() for it, to try and avoid
further misuse?

~Andrew

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  reply	other threads:[~2016-06-09 11:55 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-08 13:04 [PATCH 0/2] x86/HVM: avoid full linear->phys translations more frequently Jan Beulich
2016-06-08 13:09 ` [PATCH 1/2] x86/HVM: latch linear->phys translation results Jan Beulich
2016-06-09 11:54   ` Andrew Cooper [this message]
2016-06-09 12:13     ` Jan Beulich
2016-06-14 10:29       ` Andrew Cooper
2016-06-20 13:12     ` Tim Deegan
2016-06-20 13:44       ` Andrew Cooper
2016-06-10 15:17   ` Paul Durrant
2016-06-08 13:10 ` [PATCH 2/2] x86/HVM: use available linear->phys translations in REP MOVS/STOS handling Jan Beulich
2016-06-10 15:17   ` Paul Durrant

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