* [PATCH] x86/PV: restrict permitted instructions during memory write emulation
@ 2017-01-18 15:26 Jan Beulich
2017-01-18 16:54 ` Andrew Cooper
0 siblings, 1 reply; 5+ messages in thread
From: Jan Beulich @ 2017-01-18 15:26 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper
[-- Attachment #1: Type: text/plain, Size: 1608 bytes --]
All three code paths mean to only emulate memory writes. Refuse
emulation of any other instructions there.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
This would effectively allow us to revert 0e47f92b07 ("x86: force
EFLAGS.IF on when exiting to PV guests").
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5340,11 +5340,19 @@ static int ptwr_emulated_cmpxchg(
container_of(ctxt, struct ptwr_emulate_ctxt, ctxt));
}
+static int pv_emul_is_mem_write(const struct x86_emulate_state *state,
+ struct x86_emulate_ctxt *ctxt)
+{
+ return x86_insn_is_mem_write(state, ctxt) ? X86EMUL_OKAY
+ : X86EMUL_UNHANDLEABLE;
+}
+
static const struct x86_emulate_ops ptwr_emulate_ops = {
.read = ptwr_emulated_read,
.insn_fetch = ptwr_emulated_read,
.write = ptwr_emulated_write,
.cmpxchg = ptwr_emulated_cmpxchg,
+ .validate = pv_emul_is_mem_write,
.cpuid = pv_emul_cpuid,
};
@@ -5463,6 +5471,7 @@ static const struct x86_emulate_ops mmio
.read = x86emul_unhandleable_rw,
.insn_fetch = ptwr_emulated_read,
.write = mmio_ro_emulated_write,
+ .validate = pv_emul_is_mem_write,
.cpuid = pv_emul_cpuid,
};
@@ -5501,6 +5510,7 @@ static const struct x86_emulate_ops mmcf
.read = x86emul_unhandleable_rw,
.insn_fetch = ptwr_emulated_read,
.write = mmcfg_intercept_write,
+ .validate = pv_emul_is_mem_write,
.cpuid = pv_emul_cpuid,
};
[-- Attachment #2: x86-PV-filter-insn.patch --]
[-- Type: text/plain, Size: 1675 bytes --]
x86/PV: restrict permitted instructions during memory write emulation
All three code paths mean to only emulate memory writes. Refuse
emulation of any other instructions there.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
This would effectively allow us to revert 0e47f92b07 ("x86: force
EFLAGS.IF on when exiting to PV guests").
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5340,11 +5340,19 @@ static int ptwr_emulated_cmpxchg(
container_of(ctxt, struct ptwr_emulate_ctxt, ctxt));
}
+static int pv_emul_is_mem_write(const struct x86_emulate_state *state,
+ struct x86_emulate_ctxt *ctxt)
+{
+ return x86_insn_is_mem_write(state, ctxt) ? X86EMUL_OKAY
+ : X86EMUL_UNHANDLEABLE;
+}
+
static const struct x86_emulate_ops ptwr_emulate_ops = {
.read = ptwr_emulated_read,
.insn_fetch = ptwr_emulated_read,
.write = ptwr_emulated_write,
.cmpxchg = ptwr_emulated_cmpxchg,
+ .validate = pv_emul_is_mem_write,
.cpuid = pv_emul_cpuid,
};
@@ -5463,6 +5471,7 @@ static const struct x86_emulate_ops mmio
.read = x86emul_unhandleable_rw,
.insn_fetch = ptwr_emulated_read,
.write = mmio_ro_emulated_write,
+ .validate = pv_emul_is_mem_write,
.cpuid = pv_emul_cpuid,
};
@@ -5501,6 +5510,7 @@ static const struct x86_emulate_ops mmcf
.read = x86emul_unhandleable_rw,
.insn_fetch = ptwr_emulated_read,
.write = mmcfg_intercept_write,
+ .validate = pv_emul_is_mem_write,
.cpuid = pv_emul_cpuid,
};
[-- Attachment #3: Type: text/plain, Size: 127 bytes --]
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/PV: restrict permitted instructions during memory write emulation
2017-01-18 15:26 [PATCH] x86/PV: restrict permitted instructions during memory write emulation Jan Beulich
@ 2017-01-18 16:54 ` Andrew Cooper
2017-01-18 17:19 ` Jan Beulich
0 siblings, 1 reply; 5+ messages in thread
From: Andrew Cooper @ 2017-01-18 16:54 UTC (permalink / raw)
To: Jan Beulich, xen-devel
On 18/01/17 15:26, Jan Beulich wrote:
> All three code paths mean to only emulate memory writes. Refuse
> emulation of any other instructions there.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> This would effectively allow us to revert 0e47f92b07 ("x86: force
> EFLAGS.IF on when exiting to PV guests").
>
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -5340,11 +5340,19 @@ static int ptwr_emulated_cmpxchg(
> container_of(ctxt, struct ptwr_emulate_ctxt, ctxt));
> }
>
> +static int pv_emul_is_mem_write(const struct x86_emulate_state *state,
> + struct x86_emulate_ctxt *ctxt)
> +{
> + return x86_insn_is_mem_write(state, ctxt) ? X86EMUL_OKAY
> + : X86EMUL_UNHANDLEABLE;
> +}
> +
> static const struct x86_emulate_ops ptwr_emulate_ops = {
> .read = ptwr_emulated_read,
> .insn_fetch = ptwr_emulated_read,
> .write = ptwr_emulated_write,
> .cmpxchg = ptwr_emulated_cmpxchg,
> + .validate = pv_emul_is_mem_write,
.validate = x86_insn_is_mem_write, ?
~Andrew
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/PV: restrict permitted instructions during memory write emulation
2017-01-18 16:54 ` Andrew Cooper
@ 2017-01-18 17:19 ` Jan Beulich
2017-01-18 17:26 ` Andrew Cooper
0 siblings, 1 reply; 5+ messages in thread
From: Jan Beulich @ 2017-01-18 17:19 UTC (permalink / raw)
To: Andrew Cooper; +Cc: xen-devel
>>> On 18.01.17 at 17:54, <andrew.cooper3@citrix.com> wrote:
> On 18/01/17 15:26, Jan Beulich wrote:
>> --- a/xen/arch/x86/mm.c
>> +++ b/xen/arch/x86/mm.c
>> @@ -5340,11 +5340,19 @@ static int ptwr_emulated_cmpxchg(
>> container_of(ctxt, struct ptwr_emulate_ctxt, ctxt));
>> }
>>
>> +static int pv_emul_is_mem_write(const struct x86_emulate_state *state,
>> + struct x86_emulate_ctxt *ctxt)
>> +{
>> + return x86_insn_is_mem_write(state, ctxt) ? X86EMUL_OKAY
>> + : X86EMUL_UNHANDLEABLE;
>> +}
>> +
>> static const struct x86_emulate_ops ptwr_emulate_ops = {
>> .read = ptwr_emulated_read,
>> .insn_fetch = ptwr_emulated_read,
>> .write = ptwr_emulated_write,
>> .cmpxchg = ptwr_emulated_cmpxchg,
>> + .validate = pv_emul_is_mem_write,
>
> .validate = x86_insn_is_mem_write, ?
Nope, types don't match (and I also don't want to make them
match).
Jan
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/PV: restrict permitted instructions during memory write emulation
2017-01-18 17:19 ` Jan Beulich
@ 2017-01-18 17:26 ` Andrew Cooper
2017-01-19 8:09 ` Jan Beulich
0 siblings, 1 reply; 5+ messages in thread
From: Andrew Cooper @ 2017-01-18 17:26 UTC (permalink / raw)
To: Jan Beulich; +Cc: xen-devel
On 18/01/17 17:19, Jan Beulich wrote:
>>>> On 18.01.17 at 17:54, <andrew.cooper3@citrix.com> wrote:
>> On 18/01/17 15:26, Jan Beulich wrote:
>>> --- a/xen/arch/x86/mm.c
>>> +++ b/xen/arch/x86/mm.c
>>> @@ -5340,11 +5340,19 @@ static int ptwr_emulated_cmpxchg(
>>> container_of(ctxt, struct ptwr_emulate_ctxt, ctxt));
>>> }
>>>
>>> +static int pv_emul_is_mem_write(const struct x86_emulate_state *state,
>>> + struct x86_emulate_ctxt *ctxt)
>>> +{
>>> + return x86_insn_is_mem_write(state, ctxt) ? X86EMUL_OKAY
>>> + : X86EMUL_UNHANDLEABLE;
>>> +}
>>> +
>>> static const struct x86_emulate_ops ptwr_emulate_ops = {
>>> .read = ptwr_emulated_read,
>>> .insn_fetch = ptwr_emulated_read,
>>> .write = ptwr_emulated_write,
>>> .cmpxchg = ptwr_emulated_cmpxchg,
>>> + .validate = pv_emul_is_mem_write,
>> .validate = x86_insn_is_mem_write, ?
> Nope, types don't match (and I also don't want to make them
> match).
Oh, right.
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/PV: restrict permitted instructions during memory write emulation
2017-01-18 17:26 ` Andrew Cooper
@ 2017-01-19 8:09 ` Jan Beulich
0 siblings, 0 replies; 5+ messages in thread
From: Jan Beulich @ 2017-01-19 8:09 UTC (permalink / raw)
To: Andrew Cooper; +Cc: xen-devel
>>> On 18.01.17 at 18:26, <andrew.cooper3@citrix.com> wrote:
> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Thanks. What are your thoughts about this remark
>> This would effectively allow us to revert 0e47f92b07 ("x86: force
>> EFLAGS.IF on when exiting to PV guests").
then?
Jan
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^ permalink raw reply [flat|nested] 5+ messages in thread
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2017-01-18 15:26 [PATCH] x86/PV: restrict permitted instructions during memory write emulation Jan Beulich
2017-01-18 16:54 ` Andrew Cooper
2017-01-18 17:19 ` Jan Beulich
2017-01-18 17:26 ` Andrew Cooper
2017-01-19 8:09 ` Jan Beulich
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