Re: [RFC PATCH v2 08/38] KVM: arm64: Add EL2 special registers to vcpu context

From: Jintack Lim
Date: Tue Aug 01 2017 - 10:09:05 EST

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On Sun, Jul 30, 2017 at 3:59 PM, Christoffer Dall <cdall@xxxxxxxxxx> wrote:
> On Tue, Jul 18, 2017 at 11:58:34AM -0500, Jintack Lim wrote:
>> To support the virtual EL2 execution, we need to maintain the EL2
>> special registers such as SPSR_EL2, ELR_EL2 and SP_EL2 in vcpu context.
>>
>> Note that SP_EL2 is not accessible in EL2, so we don't need a trap
>> handler for this register.
>
> Actually, it's not accessible *in the MRS/MSR instruction* but it is of
> course accessible as the current stack pointer (which is why you need
> the state, but not the trap handler).

That is correct. I'll fix the commit message.

>
> Otherwise, the patch looks good.

Thanks!

>
> Thanks,
> -Christoffer
>
>>
>> Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx>
>> ---
>> arch/arm64/include/asm/kvm_host.h | 12 ++++++++++++
>> arch/arm64/include/asm/sysreg.h | 4 ++++
>> arch/arm64/kvm/sys_regs.c | 38 +++++++++++++++++++++++++++++++++-----
>> arch/arm64/kvm/sys_regs.h | 8 ++++++++
>> 4 files changed, 57 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 1dc4ed6..57dccde 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -171,6 +171,15 @@ enum vcpu_sysreg {
>> NR_SYS_REGS /* Nothing after this line! */
>> };
>>
>> +enum el2_special_regs {
>> + __INVALID_EL2_SPECIAL_REG__,
>> + SPSR_EL2, /* Saved Program Status Register (EL2) */
>> + ELR_EL2, /* Exception Link Register (EL2) */
>> + SP_EL2, /* Stack Pointer (EL2) */
>> +
>> + NR_EL2_SPECIAL_REGS
>> +};
>> +
>> /* 32bit mapping */
>> #define c0_MPIDR (MPIDR_EL1 * 2) /* MultiProcessor ID Register */
>> #define c0_CSSELR (CSSELR_EL1 * 2)/* Cache Size Selection Register */
>> @@ -218,6 +227,8 @@ struct kvm_cpu_context {
>> u64 sys_regs[NR_SYS_REGS];
>> u32 copro[NR_COPRO_REGS];
>> };
>> +
>> + u64 el2_special_regs[NR_EL2_SPECIAL_REGS];
>> };
>>
>> typedef struct kvm_cpu_context kvm_cpu_context_t;
>> @@ -307,6 +318,7 @@ struct kvm_vcpu_arch {
>>
>> #define vcpu_gp_regs(v) (&(v)->arch.ctxt.gp_regs)
>> #define vcpu_sys_reg(v,r) ((v)->arch.ctxt.sys_regs[(r)])
>> +#define vcpu_el2_sreg(v,r) ((v)->arch.ctxt.el2_special_regs[(r)])
>> /*
>> * CP14 and CP15 live in the same array, as they are backed by the
>> * same system registers.
>> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
>> index 9277c4a..98c32ef 100644
>> --- a/arch/arm64/include/asm/sysreg.h
>> +++ b/arch/arm64/include/asm/sysreg.h
>> @@ -268,6 +268,8 @@
>>
>> #define SYS_DACR32_EL2 sys_reg(3, 4, 3, 0, 0)
>>
>> +#define SYS_SPSR_EL2 sys_reg(3, 4, 4, 0, 0)
>> +#define SYS_ELR_EL2 sys_reg(3, 4, 4, 0, 1)
>> #define SYS_SP_EL1 sys_reg(3, 4, 4, 1, 0)
>>
>> #define SYS_IFSR32_EL2 sys_reg(3, 4, 5, 0, 1)
>> @@ -332,6 +334,8 @@
>> #define SYS_CNTVOFF_EL2 sys_reg(3, 4, 14, 0, 3)
>> #define SYS_CNTHCTL_EL2 sys_reg(3, 4, 14, 1, 0)
>>
>> +#define SYS_SP_EL2 sys_reg(3, 6, 4, 1, 0)
>> +
>> /* Common SCTLR_ELx flags. */
>> #define SCTLR_ELx_EE (1 << 25)
>> #define SCTLR_ELx_I (1 << 12)
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 1568f8b..2b3ed70 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -900,15 +900,33 @@ static inline void access_rw(struct sys_reg_params *p, u64 *sysreg)
>> *sysreg = p->regval;
>> }
>>
>> +static u64 *get_special_reg(struct kvm_vcpu *vcpu, struct sys_reg_params *p)
>> +{
>> + u64 reg = sys_reg(p->Op0, p->Op1, p->CRn, p->CRm, p->Op2);
>> +
>> + switch (reg) {
>> + case SYS_SP_EL1:
>> + return &vcpu->arch.ctxt.gp_regs.sp_el1;
>> + case SYS_ELR_EL2:
>> + return &vcpu_el2_sreg(vcpu, ELR_EL2);
>> + case SYS_SPSR_EL2:
>> + return &vcpu_el2_sreg(vcpu, SPSR_EL2);
>> + default:
>> + return NULL;
>> + };
>> +}
>> +
>> static bool trap_el2_regs(struct kvm_vcpu *vcpu,
>> struct sys_reg_params *p,
>> const struct sys_reg_desc *r)
>> {
>> - /* SP_EL1 is NOT maintained in sys_regs array */
>> - if (sys_reg(p->Op0, p->Op1, p->CRn, p->CRm, p->Op2) == SYS_SP_EL1)
>> - access_rw(p, &vcpu->arch.ctxt.gp_regs.sp_el1);
>> - else
>> - access_rw(p, &vcpu_sys_reg(vcpu, r->reg));
>> + u64 *sys_reg;
>> +
>> + sys_reg = get_special_reg(vcpu, p);
>> + if (!sys_reg)
>> + sys_reg = &vcpu_sys_reg(vcpu, r->reg);
>> +
>> + access_rw(p, sys_reg);
>>
>> return true;
>> }
>> @@ -1116,6 +1134,8 @@ static bool trap_el2_regs(struct kvm_vcpu *vcpu,
>>
>> { SYS_DESC(SYS_DACR32_EL2), NULL, reset_unknown, DACR32_EL2 },
>>
>> + { SYS_DESC(SYS_SPSR_EL2), trap_el2_regs, reset_special, SPSR_EL2, 0 },
>> + { SYS_DESC(SYS_ELR_EL2), trap_el2_regs, reset_special, ELR_EL2, 0 },
>> { SYS_DESC(SYS_SP_EL1), trap_el2_regs },
>>
>> { SYS_DESC(SYS_IFSR32_EL2), NULL, reset_unknown, IFSR32_EL2 },
>> @@ -1138,6 +1158,8 @@ static bool trap_el2_regs(struct kvm_vcpu *vcpu,
>>
>> { SYS_DESC(SYS_CNTVOFF_EL2), trap_el2_regs, reset_val, CNTVOFF_EL2, 0 },
>> { SYS_DESC(SYS_CNTHCTL_EL2), trap_el2_regs, reset_val, CNTHCTL_EL2, 0 },
>> +
>> + { SYS_DESC(SYS_SP_EL2), NULL, reset_special, SP_EL2, 0},
>> };
>>
>> static bool trap_dbgidr(struct kvm_vcpu *vcpu,
>> @@ -2271,6 +2293,8 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
>>
>> /* Catch someone adding a register without putting in reset entry. */
>> memset(&vcpu->arch.ctxt.sys_regs, 0x42, sizeof(vcpu->arch.ctxt.sys_regs));
>> + memset(&vcpu->arch.ctxt.el2_special_regs, 0x42,
>> + sizeof(vcpu->arch.ctxt.el2_special_regs));
>>
>> /* Generic chip reset first (so target could override). */
>> reset_sys_reg_descs(vcpu, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
>> @@ -2281,4 +2305,8 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
>> for (num = 1; num < NR_SYS_REGS; num++)
>> if (vcpu_sys_reg(vcpu, num) == 0x4242424242424242)
>> panic("Didn't reset vcpu_sys_reg(%zi)", num);
>> +
>> + for (num = 1; num < NR_EL2_SPECIAL_REGS; num++)
>> + if (vcpu_el2_sreg(vcpu, num) == 0x4242424242424242)
>> + panic("Didn't reset vcpu_el2_sreg(%zi)", num);
>> }
>> diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
>> index 060f534..827717b 100644
>> --- a/arch/arm64/kvm/sys_regs.h
>> +++ b/arch/arm64/kvm/sys_regs.h
>> @@ -99,6 +99,14 @@ static inline void reset_val(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r
>> vcpu_sys_reg(vcpu, r->reg) = r->val;
>> }
>>
>> +static inline void reset_special(struct kvm_vcpu *vcpu,
>> + const struct sys_reg_desc *r)
>> +{
>> + BUG_ON(!r->reg);
>> + BUG_ON(r->reg >= NR_EL2_SPECIAL_REGS);
>> + vcpu_el2_sreg(vcpu, r->reg) = r->val;
>> +}
>> +
>> static inline int cmp_sys_reg(const struct sys_reg_desc *i1,
>> const struct sys_reg_desc *i2)
>> {
>> --
>> 1.9.1
>>

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