LinuxLists.cc - [PATCH 0/2] xen: make debugreg accessors always

2021-11-25 09:23:05

Subject: [PATCH 0/2] xen: make debugreg accessors always_inline

Juergen Gross (2):
xen: make HYPERVISOR_get_debugreg() always_inline
xen: make HYPERVISOR_set_debugreg() always_inline

arch/x86/include/asm/xen/hypercall.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--
2.26.2

2021-11-25 09:23:09

by Jürgen Groß

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Subject: [PATCH 2/2] xen: make HYPERVISOR_set_debugreg() always_inline

HYPERVISOR_set_debugreg() is being called from noinstr code, so it
should be attributed "always_inline".

Fixes: 7361fac0465ba96ec8f ("x86/xen: Make set_debugreg() noinstr")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Juergen Gross <[email protected]>
---
arch/x86/include/asm/xen/hypercall.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index 28ca1119606b..e5e0fe10c692 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -281,7 +281,7 @@ HYPERVISOR_callback_op(int cmd, void *arg)
return _hypercall2(int, callback_op, cmd, arg);
}

-static inline int
+static __always_inline int
HYPERVISOR_set_debugreg(int reg, unsigned long value)
{
return _hypercall2(int, set_debugreg, reg, value);
--
2.26.2

2021-11-25 09:23:08

by Jürgen Groß

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Subject: [PATCH 1/2] xen: make HYPERVISOR_get_debugreg() always_inline

HYPERVISOR_get_debugreg() is being called from noinstr code, so it
should be attributed "always_inline".

Fixes: f4afb713e5c3a4419ba ("x86/xen: Make get_debugreg() noinstr")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Juergen Gross <[email protected]>
---
arch/x86/include/asm/xen/hypercall.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index 0575f5863b7f..28ca1119606b 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -287,7 +287,7 @@ HYPERVISOR_set_debugreg(int reg, unsigned long value)
return _hypercall2(int, set_debugreg, reg, value);
}

-static inline unsigned long
+static __always_inline unsigned long
HYPERVISOR_get_debugreg(int reg)
{
return _hypercall1(unsigned long, get_debugreg, reg);
--
2.26.2

2021-11-25 15:03:05

by Andrew Cooper

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Subject: Re: [PATCH 1/2] xen: make HYPERVISOR_get_debugreg() always_inline

On 25/11/2021 09:20, Juergen Gross wrote:
> HYPERVISOR_get_debugreg() is being called from noinstr code, so it
> should be attributed "always_inline".
>
> Fixes: f4afb713e5c3a4419ba ("x86/xen: Make get_debugreg() noinstr")
> Reported-by: kernel test robot <[email protected]>
> Signed-off-by: Juergen Gross <[email protected]>
> ---
> arch/x86/include/asm/xen/hypercall.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
> index 0575f5863b7f..28ca1119606b 100644
> --- a/arch/x86/include/asm/xen/hypercall.h
> +++ b/arch/x86/include/asm/xen/hypercall.h
> @@ -287,7 +287,7 @@ HYPERVISOR_set_debugreg(int reg, unsigned long value)
> return _hypercall2(int, set_debugreg, reg, value);
> }
>
> -static inline unsigned long
> +static __always_inline unsigned long
> HYPERVISOR_get_debugreg(int reg)
> {
> return _hypercall1(unsigned long, get_debugreg, reg);

All this is going to do is push the error one step further in.

Next, objtool will complain that hypercall_page isn't noinstr.

~Andrew

2021-11-25 15:06:17

by Jürgen Groß

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Subject: Re: [PATCH 1/2] xen: make HYPERVISOR_get_debugreg() always_inline

On 25.11.21 16:00, Andrew Cooper wrote:
> On 25/11/2021 09:20, Juergen Gross wrote:
>> HYPERVISOR_get_debugreg() is being called from noinstr code, so it
>> should be attributed "always_inline".
>>
>> Fixes: f4afb713e5c3a4419ba ("x86/xen: Make get_debugreg() noinstr")
>> Reported-by: kernel test robot <[email protected]>
>> Signed-off-by: Juergen Gross <[email protected]>
>> ---
>> arch/x86/include/asm/xen/hypercall.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
>> index 0575f5863b7f..28ca1119606b 100644
>> --- a/arch/x86/include/asm/xen/hypercall.h
>> +++ b/arch/x86/include/asm/xen/hypercall.h
>> @@ -287,7 +287,7 @@ HYPERVISOR_set_debugreg(int reg, unsigned long value)
>> return _hypercall2(int, set_debugreg, reg, value);
>> }
>>
>> -static inline unsigned long
>> +static __always_inline unsigned long
>> HYPERVISOR_get_debugreg(int reg)
>> {
>> return _hypercall1(unsigned long, get_debugreg, reg);
>
> All this is going to do is push the error one step further in.
>
> Next, objtool will complain that hypercall_page isn't noinstr.

I don't think so:

.pushsection .noinstr.text, "ax"
.balign PAGE_SIZE
SYM_CODE_START(hypercall_page)
.rept (PAGE_SIZE / 32)
UNWIND_HINT_FUNC
.skip 31, 0x90
ret
.endr

Juergen

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2021-11-25 15:42:10

by Boris Ostrovsky

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Subject: Re: [PATCH 0/2] xen: make debugreg accessors always_inline

On 11/25/21 4:20 AM, Juergen Gross wrote:
> Juergen Gross (2):
> xen: make HYPERVISOR_get_debugreg() always_inline
> xen: make HYPERVISOR_set_debugreg() always_inline
>
> arch/x86/include/asm/xen/hypercall.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Boris Ostrovsky <[email protected]>

2021-11-25 15:44:06

by Andrew Cooper

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Subject: Re: [PATCH 1/2] xen: make HYPERVISOR_get_debugreg() always_inline

On 25/11/2021 15:04, Juergen Gross wrote:
> On 25.11.21 16:00, Andrew Cooper wrote:
>> On 25/11/2021 09:20, Juergen Gross wrote:
>>> HYPERVISOR_get_debugreg() is being called from noinstr code, so it
>>> should be attributed "always_inline".
>>>
>>> Fixes: f4afb713e5c3a4419ba ("x86/xen: Make get_debugreg() noinstr")
>>> Reported-by: kernel test robot <[email protected]>
>>> Signed-off-by: Juergen Gross <[email protected]>
>>> ---
>>> arch/x86/include/asm/xen/hypercall.h | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/include/asm/xen/hypercall.h
>>> b/arch/x86/include/asm/xen/hypercall.h
>>> index 0575f5863b7f..28ca1119606b 100644
>>> --- a/arch/x86/include/asm/xen/hypercall.h
>>> +++ b/arch/x86/include/asm/xen/hypercall.h
>>> @@ -287,7 +287,7 @@ HYPERVISOR_set_debugreg(int reg, unsigned long
>>> value)
>>>       return _hypercall2(int, set_debugreg, reg, value);
>>> }
>>> -static inline unsigned long
>>> +static __always_inline unsigned long
>>> HYPERVISOR_get_debugreg(int reg)
>>> {
>>>       return _hypercall1(unsigned long, get_debugreg, reg);
>>
>> All this is going to do is push the error one step further in.
>>
>> Next, objtool will complain that hypercall_page isn't noinstr.
>
> I don't think so:
>
> .pushsection .noinstr.text, "ax"
>         .balign PAGE_SIZE
> SYM_CODE_START(hypercall_page)
>         .rept (PAGE_SIZE / 32)
>                 UNWIND_HINT_FUNC
>                 .skip 31, 0x90
>                 ret
>         .endr

/sigh yes. It would help if I was reading an up to date tree.

Sorry for the noise.

~Andrew

2021-11-26 15:19:52

by Boris Ostrovsky

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