Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native_wrmsrq()

2025-05-19 Thread Xin Li 

On 5/12/2025 1:45 AM, Xin Li (Intel) wrote:

Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
conversions when a u64 MSR value is splitted into two u32.

Signed-off-by: Xin Li (Intel) 
---
  arch/x86/coco/sev/core.c | 7 +--
  1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index ff82151f7718..b3ce6fc8b62d 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -282,12 +282,7 @@ static inline u64 sev_es_rd_ghcb_msr(void)
  
  static __always_inline void sev_es_wr_ghcb_msr(u64 val)

  {
-   u32 low, high;
-
-   low  = (u32)(val);
-   high = (u32)(val >> 32);
-
-   native_wrmsr(MSR_AMD64_SEV_ES_GHCB, low, high);
+   native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, val);
  }
  
  static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt,


Just noticed that this patch doesn't apply to tip/x86/core, I will send
it as a separate one.

Thanks!
Xin

Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native_wrmsrq()

2025-05-17 Thread Xin Li 

On 5/17/2025 6:21 AM, Ingo Molnar wrote:

Ah, indeed, it's also a startup code wrapper, which wrmsrq() doesn't
have at the moment. Fair enough.

So you want me to drop this patch then?

No, patch #3 is fine as-is in its -v1 form


Thanks for confirming.

I'll just update patch #2 as version v1A then.

Xin

Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native_wrmsrq()

2025-05-17 Thread Ingo Molnar 


* Xin Li  wrote:

> 
> >>> On 5/15/2025 10:54 AM, Xin Li wrote:
> >>> On 5/15/2025 8:27 AM, Ingo Molnar wrote:
>  
>  * Xin Li (Intel)  wrote:
>  
> > Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
> > conversions when a u64 MSR value is splitted into two u32.
> > 
>  
>  BTW., at this point we should probably just replace
>  sev_es_wr_ghcb_msr() calls with direct calls to:
>  
>  native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...);
>  
>  as sev_es_wr_ghcb_msr() is now basically an open-coded native_wrmsrq().
>  
> >>> 
> >>> I thought about it, however it looks to me that current code prefers not
> >>> to spread MSR_AMD64_SEV_ES_GHCB in 17 callsites.  And anyway it's a
> >>> __always_inline function.
> >>> 
> >>> But as you have asked, I will make the change unless someone objects.
> >> 
> >> Hi Ingo,
> >> 
> >> I took a further look and found that we can't simply replace
> >> sev_es_wr_ghcb_msr() with native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...).
> >> 
> >> There are two sev_es_wr_ghcb_msr() definitions.  One is defined in
> >> arch/x86/boot/compressed/sev.h and it references boot_wrmsr() defined in
> >> arch/x86/boot/msr.h to do MSR write.
> > 
> > Ah, indeed, it's also a startup code wrapper, which wrmsrq() doesn't
> > have at the moment. Fair enough.
> 
> So you want me to drop this patch then?

No, patch #3 is fine as-is in its -v1 form, I was wrong.

Thanks,

Ingo

Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native_wrmsrq()

2025-05-17 Thread Xin Li 


>>> On 5/15/2025 10:54 AM, Xin Li wrote:
>>> On 5/15/2025 8:27 AM, Ingo Molnar wrote:
 
 * Xin Li (Intel)  wrote:
 
> Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
> conversions when a u64 MSR value is splitted into two u32.
> 
 
 BTW., at this point we should probably just replace
 sev_es_wr_ghcb_msr() calls with direct calls to:
 
 native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...);
 
 as sev_es_wr_ghcb_msr() is now basically an open-coded native_wrmsrq().
 
>>> 
>>> I thought about it, however it looks to me that current code prefers not
>>> to spread MSR_AMD64_SEV_ES_GHCB in 17 callsites.  And anyway it's a
>>> __always_inline function.
>>> 
>>> But as you have asked, I will make the change unless someone objects.
>> 
>> Hi Ingo,
>> 
>> I took a further look and found that we can't simply replace
>> sev_es_wr_ghcb_msr() with native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...).
>> 
>> There are two sev_es_wr_ghcb_msr() definitions.  One is defined in
>> arch/x86/boot/compressed/sev.h and it references boot_wrmsr() defined in
>> arch/x86/boot/msr.h to do MSR write.
> 
> Ah, indeed, it's also a startup code wrapper, which wrmsrq() doesn't
> have at the moment. Fair enough.

So you want me to drop this patch then?

Thanks!
Xin

Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native_wrmsrq()

2025-05-17 Thread Ingo Molnar 


* Xin Li  wrote:

> On 5/15/2025 10:54 AM, Xin Li wrote:
> > On 5/15/2025 8:27 AM, Ingo Molnar wrote:
> > > 
> > > * Xin Li (Intel)  wrote:
> > > 
> > > > Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
> > > > conversions when a u64 MSR value is splitted into two u32.
> > > > 
> > > 
> > > BTW., at this point we should probably just replace
> > > sev_es_wr_ghcb_msr() calls with direct calls to:
> > > 
> > > native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...);
> > > 
> > > as sev_es_wr_ghcb_msr() is now basically an open-coded native_wrmsrq().
> > > 
> > 
> > I thought about it, however it looks to me that current code prefers not
> > to spread MSR_AMD64_SEV_ES_GHCB in 17 callsites.  And anyway it's a
> > __always_inline function.
> > 
> > But as you have asked, I will make the change unless someone objects.
> 
> Hi Ingo,
> 
> I took a further look and found that we can't simply replace
> sev_es_wr_ghcb_msr() with native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...).
> 
> There are two sev_es_wr_ghcb_msr() definitions.  One is defined in
> arch/x86/boot/compressed/sev.h and it references boot_wrmsr() defined in
> arch/x86/boot/msr.h to do MSR write.

Ah, indeed, it's also a startup code wrapper, which wrmsrq() doesn't 
have at the moment. Fair enough.

Thanks,

Ingo

Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native_wrmsrq()

2025-05-16 Thread Xin Li 

On 5/15/2025 10:54 AM, Xin Li wrote:

On 5/15/2025 8:27 AM, Ingo Molnar wrote:


* Xin Li (Intel)  wrote:


Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
conversions when a u64 MSR value is splitted into two u32.



BTW., at this point we should probably just replace
sev_es_wr_ghcb_msr() calls with direct calls to:

native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...);

as sev_es_wr_ghcb_msr() is now basically an open-coded native_wrmsrq().



I thought about it, however it looks to me that current code prefers not
to spread MSR_AMD64_SEV_ES_GHCB in 17 callsites.  And anyway it's a 
__always_inline function.


But as you have asked, I will make the change unless someone objects.


Hi Ingo,

I took a further look and found that we can't simply replace
sev_es_wr_ghcb_msr() with native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...).

There are two sev_es_wr_ghcb_msr() definitions.  One is defined in
arch/x86/boot/compressed/sev.h and it references boot_wrmsr() defined in
arch/x86/boot/msr.h to do MSR write.

The other one is defined in arch/x86/include/asm/sev-internal.h, which
uses native_wrmsrq() from arch/x86/include/asm/msr.h to write MSR.

Because:
1) arch/x86/boot/startup/sev-shared.c is included in both
arch/x86/boot/compressed/sev.c
   and
arch/x86/boot/startup/sev-startup.c

2) arch/x86/boot/startup/sev-shared.c has several references to
   sev_es_wr_ghcb_msr(),

sev_es_wr_ghcb_msr() is converted to boot_wrmsr() when included in
arch/x86/boot/compressed/sev.c or native_wrmsrq() when included in
arch/x86/boot/startup/sev-startup.c.

It would change the compressed code to use native_wrmsrq() if we remove
sev_es_wr_ghcb_msr() from arch/x86/include/asm/sev-internal.h and use 
native_wrmsrq() directly in the startup code.


We probably should get rid of boot_wrmsr() and use native_wrmsrq() in
the compressed code because they are indeed the same thing.  But as we
are so close to the v6.16 merge window, I don't think it's a good idea
to make the change right now.

So maybe I should just drop this patch and we can do the job after the 
coming merge window.


But if you think it's not a bad idea to replace native_wrmsr() with
native_wrmsrq() right now, I can keep this original patch.

Thanks!
Xin

Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native_wrmsrq()

2025-05-15 Thread Xin Li 

On 5/15/2025 8:27 AM, Ingo Molnar wrote:


* Xin Li (Intel)  wrote:


Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
conversions when a u64 MSR value is splitted into two u32.



BTW., at this point we should probably just replace
sev_es_wr_ghcb_msr() calls with direct calls to:

native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...);

as sev_es_wr_ghcb_msr() is now basically an open-coded native_wrmsrq().



I thought about it, however it looks to me that current code prefers not
to spread MSR_AMD64_SEV_ES_GHCB in 17 callsites.  And anyway it's a 
__always_inline function.


But as you have asked, I will make the change unless someone objects.

Thanks!
Xin

Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native_wrmsrq()

2025-05-15 Thread Ingo Molnar 


* Xin Li (Intel)  wrote:

> Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
> conversions when a u64 MSR value is splitted into two u32.
> 
> Signed-off-by: Xin Li (Intel) 
> ---
>  arch/x86/coco/sev/core.c | 7 +--
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> index ff82151f7718..b3ce6fc8b62d 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -282,12 +282,7 @@ static inline u64 sev_es_rd_ghcb_msr(void)
>  
>  static __always_inline void sev_es_wr_ghcb_msr(u64 val)
>  {
> - u32 low, high;
> -
> - low  = (u32)(val);
> - high = (u32)(val >> 32);
> -
> - native_wrmsr(MSR_AMD64_SEV_ES_GHCB, low, high);
> + native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, val);

BTW., at this point we should probably just replace 
sev_es_wr_ghcb_msr() calls with direct calls to:

native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...);

as sev_es_wr_ghcb_msr() is now basically an open-coded native_wrmsrq().

Thanks,

Ingo