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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [RFC PATCH] xen/arm: Replace vreg_emulate_{sysreg/cp}32 with vreg_emulate_{sysreg/cp}
Hi Julien,
On 28.07.2021 16:59, Julien Grall wrote:
> Hi Michal,
>
> On 27/07/2021 10:50, Michal Orzel wrote:
>> According to ARMv8A architecture, AArch64 registers
>> are 64bit wide even though in many cases the upper
>> 32bit is reserved. Therefore there is no need for
>> function vreg_emulate_sysreg32 on arm64.
>>
>> Ideally on arm64 there should be only one function
>> vreg_emulate_sysreg(using register_t) or
>> vreg_emulate_sysreg64(using uint64_t) but in the Xen code
>> there is a lot of functions passed both to the
>> vreg_emulate_cp* and vreg_emulate_sysreg*.
>> This would require to duplicate them which is not
>> a good solution.
>
> I think you can drop vreg_emulate_sysreg64() completely. On arm64, register_t
> is an alias to uint64_t so you could interchangeably use the type in the
> callback.
>
Yes, you are right.
> For arm32, we would still need to keep vreg_emulate_cp64.
>
>>
>> The easiest/minimal solution to fix this issue is
>> to replace vreg_emulate_{sysreg/cp}32 with
>> vreg_emulate_{sysreg/cp}. The modifed functions
>> are now taking function pointer:
>> -typedef bool (*vreg_reg_fn_t)(struct cpu_user_regs *regs,
>> register_t *r, bool read);
>> instead of:
>> -typedef bool (*vreg_reg32_fn_t)(struct cpu_user_regs *regs,
>> uint32_t *r, bool read);
>>
>> This change allows to properly use 64bit registers on arm64
>> and in case of 32bit guest the cast is done by the hardware
>> due to the 32bit registers being the lower part of 64bit ones.
>
> The HW doesn't do any cast. From the Arm Arm (D1.19.1 in ARM DDI 0487F.c):
>
> "Any modifications made to AArch32 System registers affects only those parts
> of those AArch64 registers that are
> mapped to the AArch32 System registers. Bits[63:32] of AArch64 registers,
> where they are not mapped to AArch32
> registers, are unchanged by AArch32 state execution."
>
> The registers can be set by:
> * The toolstack (via XEN_DOMCTL_set_vcpucontext). We rely on the top bits
> to always be 0. Ideally, we should 0 it in vcpu_regs_user_to_hyp() just for
> safety.
> * The PSCI CPU ON call: They should always be 0.
>
> For the rest of Xen, we expect that the top 32-bit will either be untouched
> or never be changed.
>
>>
>> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
>> ---
>> The reason for this change is to clean up the mess related to types.
>> This patch achieves that but it does not reduce the code size.
>> I'm not sure whether we want such change hence it is pushed as RFC.
>> ---
>> xen/arch/arm/vcpreg.c | 16 +++++++++++-----
>> xen/arch/arm/vtimer.c | 18 +++++++++---------
>> xen/include/asm-arm/vreg.h | 14 +++++++-------
>> 3 files changed, 27 insertions(+), 21 deletions(-)
>>
>> diff --git a/xen/arch/arm/vcpreg.c b/xen/arch/arm/vcpreg.c
>> index e3ce56d875..376a1ceee2 100644
>> --- a/xen/arch/arm/vcpreg.c
>> +++ b/xen/arch/arm/vcpreg.c
>> @@ -57,9 +57,12 @@
>> #define WRITE_SYSREG_SZ(sz, val, sysreg...) WRITE_SYSREG##sz(val, sysreg)
>> #endif
>> +#define type32_t register_t
>> +#define type64_t uint64_t
>
> Please use typedef rather than define for type. Also, please add a comment
> explaining why type32_t is defined as register_t.
>
>> +
>> /* The name is passed from the upper macro to workaround macro expansion.
>> */
>> #define TVM_REG(sz, func, reg...)
>> \
>> -static bool func(struct cpu_user_regs *regs, uint##sz##_t *r, bool read)
>> \
>> +static bool func(struct cpu_user_regs *regs, type##sz##_t *r, bool read)
>> \
>> {
>> \
>> struct vcpu *v = current;
>> \
>> bool cache_enabled = vcpu_has_cache_enabled(v);
>> \
>> @@ -83,7 +86,7 @@ static bool func(struct cpu_user_regs *regs, uint##sz##_t
>> *r, bool read) \
>> #else /* CONFIG_ARM_64 */
>> #define TVM_REG32_COMBINED(lowreg, hireg, xreg)
>> \
>> -static bool vreg_emulate_##xreg(struct cpu_user_regs *regs, uint32_t *r,
>> \
>> +static bool vreg_emulate_##xreg(struct cpu_user_regs *regs, register_t *r,
>> \
>> bool read, bool hi)
>> \
>> {
>> \
>> struct vcpu *v = current;
>> \
>> @@ -108,13 +111,13 @@ static bool vreg_emulate_##xreg(struct cpu_user_regs
>> *regs, uint32_t *r, \
>> return true;
>> \
>> }
>> \
>>
>> \
>> -static bool vreg_emulate_##lowreg(struct cpu_user_regs *regs, uint32_t *r,
>> \
>> +static bool vreg_emulate_##lowreg(struct cpu_user_regs *regs, register_t
>> *r,\
>> bool read)
>> \
>> {
>> \
>> return vreg_emulate_##xreg(regs, r, read, false);
>> \
>> }
>> \
>>
>> \
>> -static bool vreg_emulate_##hireg(struct cpu_user_regs *regs, uint32_t *r,
>> \
>> +static bool vreg_emulate_##hireg(struct cpu_user_regs *regs, register_t *r,
>> \
>> bool read)
>> \
>> {
>> \
>> return vreg_emulate_##xreg(regs, r, read, true);
>> \
>> @@ -154,13 +157,16 @@ TVM_REG32_COMBINED(MAIR0, MAIR1, MAIR_EL1)
>> TVM_REG32_COMBINED(AMAIR0, AMAIR1, AMAIR_EL1)
>> TVM_REG32(CONTEXTIDR, CONTEXTIDR_EL1)
>> +#define VREG_EMULATE_CP32(regs, hsr, fn) vreg_emulate_cp(regs, hsr, fn)
>> +#define VREG_EMULATE_CP64(regs, hsr, fn) vreg_emulate_cp64(regs, hsr, fn)
>> +
>> /* Macro to generate easily case for co-processor emulation. */
>> #define GENERATE_CASE(reg, sz) \
>> case HSR_CPREG##sz(reg): \
>> { \
>> bool res; \
>> \
>> - res = vreg_emulate_cp##sz(regs, hsr, vreg_emulate_##reg); \
>> + res = VREG_EMULATE_CP##sz(regs, hsr, vreg_emulate_##reg); \
>> ASSERT(res); \
>> break; \
>> }
>> diff --git a/xen/arch/arm/vtimer.c b/xen/arch/arm/vtimer.c
>> index 167fc6127a..17b5649a05 100644
>> --- a/xen/arch/arm/vtimer.c
>> +++ b/xen/arch/arm/vtimer.c
>> @@ -162,7 +162,7 @@ void virt_timer_restore(struct vcpu *v)
>> WRITE_SYSREG(v->arch.virt_timer.ctl, CNTV_CTL_EL0);
>> }
>> -static bool vtimer_cntp_ctl(struct cpu_user_regs *regs, uint32_t *r, bool
>> read)
>> +static bool vtimer_cntp_ctl(struct cpu_user_regs *regs, register_t *r, bool
>> read)
>> {
>> struct vcpu *v = current;
>> s_time_t expires;
>> @@ -176,7 +176,7 @@ static bool vtimer_cntp_ctl(struct cpu_user_regs *regs,
>> uint32_t *r, bool read)
>> }
>> else
>> {
>> - uint32_t ctl = *r & ~CNTx_CTL_PENDING;
>> + register_t ctl = *r & ~CNTx_CTL_PENDING;
> You will still end up to mask the top 32-bit because CTx_CTL_PENDING is an
> unsigned 32-bit. I think we should not touch them top 32-bit at all so
> CNTx_CTL_PENDING (and probably CNT_x_CTL_ENABLE) should be defined as 1UL <<
> X.
>
Ok I will not modify the timer functions apart from changing the argument's
type.
I will modify CNTx_CTL_PENDING and CNT_x_CTL_ENABLE to be ul.
>> if ( ctl & CNTx_CTL_ENABLE )
>> ctl |= v->arch.phys_timer.ctl & CNTx_CTL_PENDING;
>> v->arch.phys_timer.ctl = ctl;
>> @@ -197,7 +197,7 @@ static bool vtimer_cntp_ctl(struct cpu_user_regs *regs,
>> uint32_t *r, bool read)
>> return true;
>> }
>> -static bool vtimer_cntp_tval(struct cpu_user_regs *regs, uint32_t *r,
>> +static bool vtimer_cntp_tval(struct cpu_user_regs *regs, register_t *r,
>> bool read)
>> {
>> struct vcpu *v = current;
>> @@ -211,11 +211,11 @@ static bool vtimer_cntp_tval(struct cpu_user_regs
>> *regs, uint32_t *r,
>> if ( read )
>> {
>> - *r = (uint32_t)((v->arch.phys_timer.cval - cntpct) & 0xffffffffull);
>> + *r = (register_t)((v->arch.phys_timer.cval - cntpct) &
>> 0xffffffffull);
>
> This is computing the TimerVal is held in the first 32-bit of the registers.
> So I think this should stick to (uint32_t) here.
>
>> }
>> else
>> {
>> - v->arch.phys_timer.cval = cntpct + (uint64_t)(int32_t)*r;
>> + v->arch.phys_timer.cval = cntpct + (uint64_t)(register_t)*r;
>
> This is not quite the same as before. We were using the first 32-bit as a
> signed value. Now, you are using the full register as a unsigned value.
>
>> if ( v->arch.phys_timer.ctl & CNTx_CTL_ENABLE )
>> {
>> v->arch.phys_timer.ctl &= ~CNTx_CTL_PENDING;
>> @@ -274,10 +274,10 @@ static bool vtimer_emulate_cp32(struct cpu_user_regs
>> *regs, union hsr hsr)
>> switch ( hsr.bits & HSR_CP32_REGS_MASK )
>> {
>> case HSR_CPREG32(CNTP_CTL):
>> - return vreg_emulate_cp32(regs, hsr, vtimer_cntp_ctl);
>> + return vreg_emulate_cp(regs, hsr, vtimer_cntp_ctl);
>> case HSR_CPREG32(CNTP_TVAL):
>> - return vreg_emulate_cp32(regs, hsr, vtimer_cntp_tval);
>> + return vreg_emulate_cp(regs, hsr, vtimer_cntp_tval);
>> default:
>> return false;
>> @@ -316,9 +316,9 @@ static bool vtimer_emulate_sysreg(struct cpu_user_regs
>> *regs, union hsr hsr)
>> switch ( hsr.bits & HSR_SYSREG_REGS_MASK )
>> {
>> case HSR_SYSREG_CNTP_CTL_EL0:
>> - return vreg_emulate_sysreg32(regs, hsr, vtimer_cntp_ctl);
>> + return vreg_emulate_sysreg(regs, hsr, vtimer_cntp_ctl);
>> case HSR_SYSREG_CNTP_TVAL_EL0:
>> - return vreg_emulate_sysreg32(regs, hsr, vtimer_cntp_tval);
>> + return vreg_emulate_sysreg(regs, hsr, vtimer_cntp_tval);
>> case HSR_SYSREG_CNTP_CVAL_EL0:
>> return vreg_emulate_sysreg64(regs, hsr, vtimer_cntp_cval);
>> diff --git a/xen/include/asm-arm/vreg.h b/xen/include/asm-arm/vreg.h
>> index 1253753833..cef55aabea 100644
>> --- a/xen/include/asm-arm/vreg.h
>> +++ b/xen/include/asm-arm/vreg.h
>> @@ -4,13 +4,13 @@
>> #ifndef __ASM_ARM_VREG__
>> #define __ASM_ARM_VREG__
>> -typedef bool (*vreg_reg32_fn_t)(struct cpu_user_regs *regs, uint32_t *r,
>> +typedef bool (*vreg_reg_fn_t)(struct cpu_user_regs *regs, register_t *r,
>> bool read);
>> typedef bool (*vreg_reg64_fn_t)(struct cpu_user_regs *regs, uint64_t *r,
>> bool read);
>> -static inline bool vreg_emulate_cp32(struct cpu_user_regs *regs, union
>> hsr hsr,
>> - vreg_reg32_fn_t fn)
>> +static inline bool vreg_emulate_cp(struct cpu_user_regs *regs, union hsr
>> hsr,
>> + vreg_reg_fn_t fn)
>
> The new name will add some confusion because now we have vreg_emulate_cp()
> (for 32-bit access) and vreg_emulate_c64() (for 64-bit access).
>
> So I would rather keep the current naming.
>
We can do like that:
-on arm32 there will be vreg_emulate_cp32 with register_t and vreg_emulate_cp64.
-on arm64 there will be only vreg_emulate_sysreg with register_t.
Does it sound ok or do you want to drop this change completely?
If it is ok I will push v2 without RFC tag.
>> {
>> struct hsr_cp32 cp32 = hsr.cp32;
>> /*
>> @@ -18,7 +18,7 @@ static inline bool vreg_emulate_cp32(struct cpu_user_regs
>> *regs, union hsr hsr,
>> * implementation error in the emulation (such as not correctly
>> * setting r).
>> */
>> - uint32_t r = 0;
>> + register_t r = 0;
>> bool ret;
>> if ( !cp32.read )
>> @@ -64,11 +64,11 @@ static inline bool vreg_emulate_cp64(struct
>> cpu_user_regs *regs, union hsr hsr,
>> }
>> #ifdef CONFIG_ARM_64
>> -static inline bool vreg_emulate_sysreg32(struct cpu_user_regs *regs, union
>> hsr hsr,
>> - vreg_reg32_fn_t fn)
>> +static inline bool vreg_emulate_sysreg(struct cpu_user_regs *regs, union
>> hsr hsr,
>> + vreg_reg_fn_t fn)
>> {
>> struct hsr_sysreg sysreg = hsr.sysreg;
>> - uint32_t r = 0;
>> + register_t r = 0;
>> bool ret;
>> if ( !sysreg.read )
>>
>
> Cheers,
>
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