* [PATCH] x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads
@ 2015-05-08 12:08 Jan Beulich
2015-05-08 12:36 ` Andrew Cooper
2015-05-11 15:15 ` Konrad Rzeszutek Wilk
0 siblings, 2 replies; 4+ messages in thread
From: Jan Beulich @ 2015-05-08 12:08 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper, Keir Fraser
[-- Attachment #1: Type: text/plain, Size: 600 bytes --]
1- or 2-byte operations never alter the high halves of registers.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2234,7 +2234,7 @@ static int emulate_privileged_op(struct
if ( op_bytes == 4 )
regs->eax = 0;
else
- regs->eax &= ~((1u << (op_bytes * 8)) - 1);
+ regs->eax &= ~((1 << (op_bytes * 8)) - 1);
regs->eax |= guest_io_read(port, op_bytes, v, regs);
}
bpmatch = check_guest_io_breakpoint(v, port, op_bytes);
[-- Attachment #2: x86-PV-IO-read-high-bits.patch --]
[-- Type: text/plain, Size: 667 bytes --]
x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads
1- or 2-byte operations never alter the high halves of registers.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2234,7 +2234,7 @@ static int emulate_privileged_op(struct
if ( op_bytes == 4 )
regs->eax = 0;
else
- regs->eax &= ~((1u << (op_bytes * 8)) - 1);
+ regs->eax &= ~((1 << (op_bytes * 8)) - 1);
regs->eax |= guest_io_read(port, op_bytes, v, regs);
}
bpmatch = check_guest_io_breakpoint(v, port, op_bytes);
[-- Attachment #3: Type: text/plain, Size: 126 bytes --]
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads
2015-05-08 12:08 [PATCH] x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads Jan Beulich
@ 2015-05-08 12:36 ` Andrew Cooper
2015-05-11 15:15 ` Konrad Rzeszutek Wilk
1 sibling, 0 replies; 4+ messages in thread
From: Andrew Cooper @ 2015-05-08 12:36 UTC (permalink / raw)
To: Jan Beulich, xen-devel; +Cc: Keir Fraser
On 08/05/15 13:08, Jan Beulich wrote:
> 1- or 2-byte operations never alter the high halves of registers.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
>
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -2234,7 +2234,7 @@ static int emulate_privileged_op(struct
> if ( op_bytes == 4 )
> regs->eax = 0;
> else
> - regs->eax &= ~((1u << (op_bytes * 8)) - 1);
> + regs->eax &= ~((1 << (op_bytes * 8)) - 1);
> regs->eax |= guest_io_read(port, op_bytes, v, regs);
> }
> bpmatch = check_guest_io_breakpoint(v, port, op_bytes);
>
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads
2015-05-08 12:08 [PATCH] x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads Jan Beulich
2015-05-08 12:36 ` Andrew Cooper
@ 2015-05-11 15:15 ` Konrad Rzeszutek Wilk
2015-05-12 9:27 ` Jan Beulich
1 sibling, 1 reply; 4+ messages in thread
From: Konrad Rzeszutek Wilk @ 2015-05-11 15:15 UTC (permalink / raw)
To: Jan Beulich; +Cc: xen-devel, Keir Fraser, Andrew Cooper
On Fri, May 08, 2015 at 01:08:05PM +0100, Jan Beulich wrote:
> 1- or 2-byte operations never alter the high halves of registers.
>
That is impressive. How possibly did you spot this?
Was it due to reviewing some other code that got you looking
at this?
Thanks!
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -2234,7 +2234,7 @@ static int emulate_privileged_op(struct
> if ( op_bytes == 4 )
> regs->eax = 0;
> else
> - regs->eax &= ~((1u << (op_bytes * 8)) - 1);
> + regs->eax &= ~((1 << (op_bytes * 8)) - 1);
> regs->eax |= guest_io_read(port, op_bytes, v, regs);
> }
> bpmatch = check_guest_io_breakpoint(v, port, op_bytes);
>
>
>
> x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads
>
> 1- or 2-byte operations never alter the high halves of registers.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -2234,7 +2234,7 @@ static int emulate_privileged_op(struct
> if ( op_bytes == 4 )
> regs->eax = 0;
> else
> - regs->eax &= ~((1u << (op_bytes * 8)) - 1);
> + regs->eax &= ~((1 << (op_bytes * 8)) - 1);
> regs->eax |= guest_io_read(port, op_bytes, v, regs);
> }
> bpmatch = check_guest_io_breakpoint(v, port, op_bytes);
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads
2015-05-11 15:15 ` Konrad Rzeszutek Wilk
@ 2015-05-12 9:27 ` Jan Beulich
0 siblings, 0 replies; 4+ messages in thread
From: Jan Beulich @ 2015-05-12 9:27 UTC (permalink / raw)
To: Konrad Rzeszutek Wilk; +Cc: Andrew Cooper, Keir Fraser, xen-devel
>>> On 11.05.15 at 17:15, <konrad.wilk@oracle.com> wrote:
> On Fri, May 08, 2015 at 01:08:05PM +0100, Jan Beulich wrote:
>> 1- or 2-byte operations never alter the high halves of registers.
>>
>
> That is impressive. How possibly did you spot this?
>
> Was it due to reviewing some other code that got you looking
> at this?
Yes, while reviewing the patches from Roger (or rather investigating
the need to revert).
Jan
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2015-05-12 9:47 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2015-05-08 12:08 [PATCH] x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads Jan Beulich
2015-05-08 12:36 ` Andrew Cooper
2015-05-11 15:15 ` Konrad Rzeszutek Wilk
2015-05-12 9:27 ` Jan Beulich
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