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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH] x86emul: correct LFS et al handling for 64-bit mode
Date: Thu, 12 Dec 2019 11:37:10 +0000	[thread overview]
Message-ID: <c49ca1fb-ce62-6668-966f-7a75150687fa@citrix.com> (raw)
In-Reply-To: <43160a9d-2738-0b1d-01ef-b3ad8f1c50dc@suse.com>

On 12/12/2019 10:11, Jan Beulich wrote:
> On 11.12.2019 21:57, Andrew Cooper wrote:
>> On 11/12/2019 09:28, Jan Beulich wrote:
>>> AMD and friends explicitly specify that 64-bit operands aren't possible
>>> for these insns. Nevertheless REX.W isn't fully ignored: It still
>>> cancels a possible operand size override (0x66). Intel otoh explicitly
>>> provides for 64-bit operands on the respective insn page of the SDM.
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>> It is definitely more than just these.  Near jumps have per-vendor
>> behaviour on how long the instruction is, whereas far jump/calls are in
>> the same category as these by the looks of things.
> But you don't expect me to fold all of these into one patch, do
> you?

short jmp certainly not, but far jmp/call is just two extra case
statements in this new code block, no?

> We have _some_ vendor dependent behavior already, and I'm
> slowly adding to it. Our far call/jmp support is rather
> incomplete in other ways anyway.

There is different truncation behaviour for %rip which needs altering,
but that is a separate area of code.  Anything else?

~Andrew

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  reply	other threads:[~2019-12-12 11:37 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-11  9:28 [Xen-devel] [PATCH] x86emul: correct LFS et al handling for 64-bit mode Jan Beulich
2019-12-11 20:57 ` Andrew Cooper
2019-12-12 10:11   ` Jan Beulich
2019-12-12 11:37     ` Andrew Cooper [this message]
2019-12-12 13:05       ` Jan Beulich
2019-12-12 14:20         ` Andrew Cooper
2019-12-12 15:55           ` Jan Beulich

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