Re: [PATCH 5/9] arm/mm: Get rid of READ/WRITE_SYSREG32
On 22/04/2021 12:47, Michal Orzel wrote: Hi Julien, Hi Michal, On 20.04.2021 15:37, Julien Grall wrote: Hi Michal, On 20/04/2021 08:08, Michal Orzel wrote: AArch64 system registers are 64bit whereas AArch32 ones are 32bit or 64bit. MSR/MRS are expecting 64bit values thus we should get rid of helpers READ/WRITE_SYSREG32 in favour of using READ/WRITE_SYSREG. We should also use register_t type when reading sysregs which can correspond to uint64_t or uint32_t. Even though many AArch64 sysregs have upper 32bit reserved it does not mean that they can't be widen in the future. Modify SCTLR_EL2 accesses to use READ/WRITE_SYSREG. SCTLR_EL2 already has bits defined in the range [32:63]. So this change is going to have a side effect as AFAICT head.S will not touch those bits. So they are now going to be preserved. The Arm Arm defines them as unknown if implemented. Therefore shouldn't we zero them somewhere else? SCTLR_EL2 is set in head.S using SCTLR_EL2_SET which means that we are zeroing the upper 32bit half. Ah! I couldn't find the place doing it. Thanks! I think it is important to point in the commit message this is just a latent bug because the top 32-bit was not used by Xen. Can you update the commit message? Cheers, -- Julien Grall
Re: [PATCH 5/9] arm/mm: Get rid of READ/WRITE_SYSREG32
Hi Julien,
On 20.04.2021 15:37, Julien Grall wrote:
> Hi Michal,
>
> On 20/04/2021 08:08, Michal Orzel wrote:
>> AArch64 system registers are 64bit whereas AArch32 ones
>> are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
>> we should get rid of helpers READ/WRITE_SYSREG32
>> in favour of using READ/WRITE_SYSREG.
>> We should also use register_t type when reading sysregs
>> which can correspond to uint64_t or uint32_t.
>> Even though many AArch64 sysregs have upper 32bit reserved
>> it does not mean that they can't be widen in the future.
>>
>> Modify SCTLR_EL2 accesses to use READ/WRITE_SYSREG.
>
> SCTLR_EL2 already has bits defined in the range [32:63]. So this change is
> going to have a side effect as AFAICT head.S will not touch those bits. So
> they are now going to be preserved.
>
> The Arm Arm defines them as unknown if implemented. Therefore shouldn't we
> zero them somewhere else?
>
SCTLR_EL2 is set in head.S using SCTLR_EL2_SET which means that we are zeroing
the upper 32bit half.
> In any case, I think the commit message ought to contain an analysis for
> system registers that happened to have bits defined in the range [32:63].
>
>>
>> Signed-off-by: Michal Orzel
>> ---
>> xen/arch/arm/mm.c | 2 +-
>> xen/arch/arm/traps.c | 2 +-
>> 2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
>> index 59f8a3f15f..0e07335291 100644
>> --- a/xen/arch/arm/mm.c
>> +++ b/xen/arch/arm/mm.c
>> @@ -613,7 +613,7 @@ void __init remove_early_mappings(void)
>> */
>> static void xen_pt_enforce_wnx(void)
>> {
>> - WRITE_SYSREG32(READ_SYSREG32(SCTLR_EL2) | SCTLR_Axx_ELx_WXN, SCTLR_EL2);
>> + WRITE_SYSREG(READ_SYSREG(SCTLR_EL2) | SCTLR_Axx_ELx_WXN, SCTLR_EL2);
>> /*
>> * The TLBs may cache SCTLR_EL2.WXN. So ensure it is synchronized
>> * before flushing the TLBs.
>> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
>> index c7acdb2087..e7384381cc 100644
>> --- a/xen/arch/arm/traps.c
>> +++ b/xen/arch/arm/traps.c
>> @@ -915,7 +915,7 @@ static void _show_registers(const struct cpu_user_regs
>> *regs,
>> printk(" VTTBR_EL2: %016"PRIx64"\n", ctxt->vttbr_el2);
>> printk("\n");
>> - printk(" SCTLR_EL2: %08"PRIx32"\n", READ_SYSREG32(SCTLR_EL2));
>> + printk(" SCTLR_EL2: %"PRIregister"\n", READ_SYSREG(SCTLR_EL2));
>> printk(" HCR_EL2: %"PRIregister"\n", READ_SYSREG(HCR_EL2));
>> printk(" TTBR0_EL2: %016"PRIx64"\n", READ_SYSREG64(TTBR0_EL2));
>> printk("\n");
>>
>
> Cheers,
>
Cheers,
Michal
Re: [PATCH 5/9] arm/mm: Get rid of READ/WRITE_SYSREG32
Hi Michal,
On 20/04/2021 08:08, Michal Orzel wrote:
AArch64 system registers are 64bit whereas AArch32 ones
are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
we should get rid of helpers READ/WRITE_SYSREG32
in favour of using READ/WRITE_SYSREG.
We should also use register_t type when reading sysregs
which can correspond to uint64_t or uint32_t.
Even though many AArch64 sysregs have upper 32bit reserved
it does not mean that they can't be widen in the future.
Modify SCTLR_EL2 accesses to use READ/WRITE_SYSREG.
SCTLR_EL2 already has bits defined in the range [32:63]. So this change
is going to have a side effect as AFAICT head.S will not touch those
bits. So they are now going to be preserved.
The Arm Arm defines them as unknown if implemented. Therefore shouldn't
we zero them somewhere else?
In any case, I think the commit message ought to contain an analysis for
system registers that happened to have bits defined in the range [32:63].
Signed-off-by: Michal Orzel
---
xen/arch/arm/mm.c| 2 +-
xen/arch/arm/traps.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 59f8a3f15f..0e07335291 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -613,7 +613,7 @@ void __init remove_early_mappings(void)
*/
static void xen_pt_enforce_wnx(void)
{
-WRITE_SYSREG32(READ_SYSREG32(SCTLR_EL2) | SCTLR_Axx_ELx_WXN, SCTLR_EL2);
+WRITE_SYSREG(READ_SYSREG(SCTLR_EL2) | SCTLR_Axx_ELx_WXN, SCTLR_EL2);
/*
* The TLBs may cache SCTLR_EL2.WXN. So ensure it is synchronized
* before flushing the TLBs.
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index c7acdb2087..e7384381cc 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -915,7 +915,7 @@ static void _show_registers(const struct cpu_user_regs
*regs,
printk(" VTTBR_EL2: %016"PRIx64"\n", ctxt->vttbr_el2);
printk("\n");
-printk(" SCTLR_EL2: %08"PRIx32"\n", READ_SYSREG32(SCTLR_EL2));
+printk(" SCTLR_EL2: %"PRIregister"\n", READ_SYSREG(SCTLR_EL2));
printk(" HCR_EL2: %"PRIregister"\n", READ_SYSREG(HCR_EL2));
printk(" TTBR0_EL2: %016"PRIx64"\n", READ_SYSREG64(TTBR0_EL2));
printk("\n");
Cheers,
--
Julien Grall
[PATCH 5/9] arm/mm: Get rid of READ/WRITE_SYSREG32
AArch64 system registers are 64bit whereas AArch32 ones
are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
we should get rid of helpers READ/WRITE_SYSREG32
in favour of using READ/WRITE_SYSREG.
We should also use register_t type when reading sysregs
which can correspond to uint64_t or uint32_t.
Even though many AArch64 sysregs have upper 32bit reserved
it does not mean that they can't be widen in the future.
Modify SCTLR_EL2 accesses to use READ/WRITE_SYSREG.
Signed-off-by: Michal Orzel
---
xen/arch/arm/mm.c| 2 +-
xen/arch/arm/traps.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 59f8a3f15f..0e07335291 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -613,7 +613,7 @@ void __init remove_early_mappings(void)
*/
static void xen_pt_enforce_wnx(void)
{
-WRITE_SYSREG32(READ_SYSREG32(SCTLR_EL2) | SCTLR_Axx_ELx_WXN, SCTLR_EL2);
+WRITE_SYSREG(READ_SYSREG(SCTLR_EL2) | SCTLR_Axx_ELx_WXN, SCTLR_EL2);
/*
* The TLBs may cache SCTLR_EL2.WXN. So ensure it is synchronized
* before flushing the TLBs.
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index c7acdb2087..e7384381cc 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -915,7 +915,7 @@ static void _show_registers(const struct cpu_user_regs
*regs,
printk(" VTTBR_EL2: %016"PRIx64"\n", ctxt->vttbr_el2);
printk("\n");
-printk(" SCTLR_EL2: %08"PRIx32"\n", READ_SYSREG32(SCTLR_EL2));
+printk(" SCTLR_EL2: %"PRIregister"\n", READ_SYSREG(SCTLR_EL2));
printk(" HCR_EL2: %"PRIregister"\n", READ_SYSREG(HCR_EL2));
printk(" TTBR0_EL2: %016"PRIx64"\n", READ_SYSREG64(TTBR0_EL2));
printk("\n");
--
2.29.0
