[PATCH V3 2/2] KVM: selftests: Change MDSCR_EL1 register holding variables as uint64_t

[PATCH V3 2/2] KVM: selftests: Change MDSCR_EL1 register holding variables as uint64_t

[Anshuman Khandual]

Change MDSCR_EL1 register holding local variables as uint64_t that reflects
its true register width as well.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: kvm@vger.kernel.org
Cc: kvmarm@lists.linux.dev
Cc: linux-kernel@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 tools/testing/selftests/kvm/arm64/debug-exceptions.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/debug-exceptions.c b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
index c7fb55c9135b..e34963956fbc 100644
--- a/tools/testing/selftests/kvm/arm64/debug-exceptions.c
+++ b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
@@ -140,7 +140,7 @@ static void enable_os_lock(void)
 
 static void enable_monitor_debug_exceptions(void)
 {
-	uint32_t mdscr;
+	uint64_t mdscr;
 
 	asm volatile("msr daifclr, #8");
 
@@ -223,7 +223,7 @@ void install_hw_bp_ctx(uint8_t addr_bp, uint8_t ctx_bp, uint64_t addr,
 
 static void install_ss(void)
 {
-	uint32_t mdscr;
+	uint64_t mdscr;
 
 	asm volatile("msr daifclr, #8");
 
-- 
2.25.1

Re: [PATCH V3 2/2] KVM: selftests: Change MDSCR_EL1 register holding variables as uint64_t

[Marc Zyngier]

On Tue, 10 Jun 2025 06:31:28 +0100,
Anshuman Khandual <anshuman.khandual@arm.com> wrote:
> 
> Change MDSCR_EL1 register holding local variables as uint64_t that reflects
> its true register width as well.
> 
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Oliver Upton <oliver.upton@linux.dev>
> Cc: Joey Gouly <joey.gouly@arm.com>
> Cc: kvm@vger.kernel.org
> Cc: kvmarm@lists.linux.dev
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-kselftest@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
>  tools/testing/selftests/kvm/arm64/debug-exceptions.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/arm64/debug-exceptions.c b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> index c7fb55c9135b..e34963956fbc 100644
> --- a/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> +++ b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> @@ -140,7 +140,7 @@ static void enable_os_lock(void)
>  
>  static void enable_monitor_debug_exceptions(void)
>  {
> -	uint32_t mdscr;
> +	uint64_t mdscr;
>  
>  	asm volatile("msr daifclr, #8");
>  
> @@ -223,7 +223,7 @@ void install_hw_bp_ctx(uint8_t addr_bp, uint8_t ctx_bp, uint64_t addr,
>  
>  static void install_ss(void)
>  {
> -	uint32_t mdscr;
> +	uint64_t mdscr;
>  
>  	asm volatile("msr daifclr, #8");
>  

Why change this in the place that matters *the least*?

arch/arm64/kernel/debug-monitors.c is full of 32bit manipulation of
this register, and that's only one example of it. So if you are going
to change this, please do it fully, not as a random change in a random
file.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH V3 2/2] KVM: selftests: Change MDSCR_EL1 register holding variables as uint64_t

[Anshuman Khandual]

On 10/06/25 10:31 PM, Marc Zyngier wrote:
> On Tue, 10 Jun 2025 06:31:28 +0100,
> Anshuman Khandual <anshuman.khandual@arm.com> wrote:
>>
>> Change MDSCR_EL1 register holding local variables as uint64_t that reflects
>> its true register width as well.
>>
>> Cc: Marc Zyngier <maz@kernel.org>
>> Cc: Oliver Upton <oliver.upton@linux.dev>
>> Cc: Joey Gouly <joey.gouly@arm.com>
>> Cc: kvm@vger.kernel.org
>> Cc: kvmarm@lists.linux.dev
>> Cc: linux-kernel@vger.kernel.org
>> Cc: linux-kselftest@vger.kernel.org
>> Cc: linux-arm-kernel@lists.infradead.org
>> Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>>  tools/testing/selftests/kvm/arm64/debug-exceptions.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/testing/selftests/kvm/arm64/debug-exceptions.c b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
>> index c7fb55c9135b..e34963956fbc 100644
>> --- a/tools/testing/selftests/kvm/arm64/debug-exceptions.c
>> +++ b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
>> @@ -140,7 +140,7 @@ static void enable_os_lock(void)
>>  
>>  static void enable_monitor_debug_exceptions(void)
>>  {
>> -	uint32_t mdscr;
>> +	uint64_t mdscr;
>>  
>>  	asm volatile("msr daifclr, #8");
>>  
>> @@ -223,7 +223,7 @@ void install_hw_bp_ctx(uint8_t addr_bp, uint8_t ctx_bp, uint64_t addr,
>>  
>>  static void install_ss(void)
>>  {
>> -	uint32_t mdscr;
>> +	uint64_t mdscr;
>>  
>>  	asm volatile("msr daifclr, #8");
>>  
> 
> Why change this in the place that matters *the least*?
> 
> arch/arm64/kernel/debug-monitors.c is full of 32bit manipulation of
> this register, and that's only one example of it. So if you are going
> to change this, please do it fully, not as a random change in a random
> file.

The first patch in this series changes mdscr system register to 64 bit
in the mentioned file (i.e arch/arm64/kernel/debug-monitors.c). 

> 
> Thanks,
> 
> 	M.
> 

Re: [PATCH V3 2/2] KVM: selftests: Change MDSCR_EL1 register holding variables as uint64_t

[Mark Rutland]

On Wed, Jun 11, 2025 at 09:15:10AM +0530, Anshuman Khandual wrote:
> 
> 
> On 10/06/25 10:31 PM, Marc Zyngier wrote:
> > On Tue, 10 Jun 2025 06:31:28 +0100,
> > Anshuman Khandual <anshuman.khandual@arm.com> wrote:
> >>
> >> Change MDSCR_EL1 register holding local variables as uint64_t that reflects
> >> its true register width as well.
> >>
> >> Cc: Marc Zyngier <maz@kernel.org>
> >> Cc: Oliver Upton <oliver.upton@linux.dev>
> >> Cc: Joey Gouly <joey.gouly@arm.com>
> >> Cc: kvm@vger.kernel.org
> >> Cc: kvmarm@lists.linux.dev
> >> Cc: linux-kernel@vger.kernel.org
> >> Cc: linux-kselftest@vger.kernel.org
> >> Cc: linux-arm-kernel@lists.infradead.org
> >> Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> >> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> >> ---
> >>  tools/testing/selftests/kvm/arm64/debug-exceptions.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/tools/testing/selftests/kvm/arm64/debug-exceptions.c b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> >> index c7fb55c9135b..e34963956fbc 100644
> >> --- a/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> >> +++ b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> >> @@ -140,7 +140,7 @@ static void enable_os_lock(void)
> >>  
> >>  static void enable_monitor_debug_exceptions(void)
> >>  {
> >> -	uint32_t mdscr;
> >> +	uint64_t mdscr;
> >>  
> >>  	asm volatile("msr daifclr, #8");
> >>  
> >> @@ -223,7 +223,7 @@ void install_hw_bp_ctx(uint8_t addr_bp, uint8_t ctx_bp, uint64_t addr,
> >>  
> >>  static void install_ss(void)
> >>  {
> >> -	uint32_t mdscr;
> >> +	uint64_t mdscr;
> >>  
> >>  	asm volatile("msr daifclr, #8");
> >>  
> > 
> > Why change this in the place that matters *the least*?
> > 
> > arch/arm64/kernel/debug-monitors.c is full of 32bit manipulation of
> > this register, and that's only one example of it. So if you are going
> > to change this, please do it fully, not as a random change in a random
> > file.
> 
> The first patch in this series changes mdscr system register to 64 bit
> in the mentioned file (i.e arch/arm64/kernel/debug-monitors.c). 

You did not Cc Marc on oatch 1 or the cover letter. KVM folk are only
Cc'd on patch 2.

Marc, for context the series is:

  https://lore.kernel.org/linux-arm-kernel/20250610053128.4118784-1-anshuman.khandual@arm.com/

... and I've asked Anshuman to better describe the rationale.

Mark.

Re: [PATCH V3 2/2] KVM: selftests: Change MDSCR_EL1 register holding variables as uint64_t

[Marc Zyngier]

On Wed, 11 Jun 2025 04:45:10 +0100,
Anshuman Khandual <anshuman.khandual@arm.com> wrote:
> 
> 
> 
> On 10/06/25 10:31 PM, Marc Zyngier wrote:
> > On Tue, 10 Jun 2025 06:31:28 +0100,
> > Anshuman Khandual <anshuman.khandual@arm.com> wrote:
> >>
> >> Change MDSCR_EL1 register holding local variables as uint64_t that reflects
> >> its true register width as well.
> >>
> >> Cc: Marc Zyngier <maz@kernel.org>
> >> Cc: Oliver Upton <oliver.upton@linux.dev>
> >> Cc: Joey Gouly <joey.gouly@arm.com>
> >> Cc: kvm@vger.kernel.org
> >> Cc: kvmarm@lists.linux.dev
> >> Cc: linux-kernel@vger.kernel.org
> >> Cc: linux-kselftest@vger.kernel.org
> >> Cc: linux-arm-kernel@lists.infradead.org
> >> Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> >> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> >> ---
> >>  tools/testing/selftests/kvm/arm64/debug-exceptions.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/tools/testing/selftests/kvm/arm64/debug-exceptions.c b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> >> index c7fb55c9135b..e34963956fbc 100644
> >> --- a/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> >> +++ b/tools/testing/selftests/kvm/arm64/debug-exceptions.c
> >> @@ -140,7 +140,7 @@ static void enable_os_lock(void)
> >>  
> >>  static void enable_monitor_debug_exceptions(void)
> >>  {
> >> -	uint32_t mdscr;
> >> +	uint64_t mdscr;
> >>  
> >>  	asm volatile("msr daifclr, #8");
> >>  
> >> @@ -223,7 +223,7 @@ void install_hw_bp_ctx(uint8_t addr_bp, uint8_t ctx_bp, uint64_t addr,
> >>  
> >>  static void install_ss(void)
> >>  {
> >> -	uint32_t mdscr;
> >> +	uint64_t mdscr;
> >>  
> >>  	asm volatile("msr daifclr, #8");
> >>  
> > 
> > Why change this in the place that matters *the least*?
> > 
> > arch/arm64/kernel/debug-monitors.c is full of 32bit manipulation of
> > this register, and that's only one example of it. So if you are going
> > to change this, please do it fully, not as a random change in a random
> > file.
> 
> The first patch in this series changes mdscr system register to 64 bit
> in the mentioned file (i.e arch/arm64/kernel/debug-monitors.c).

Then please Cc me on the series, and not patches at random. Context matters.

	M.

-- 
Without deviation from the norm, progress is not possible.