Re: [PATCH v2 05/21] KVM: arm64: Protect TPIDRRO_EL0 across guest entry/exit

[Jinjie Ruan]

在 2026/9/19 0:13, Will Deacon 写道:
> From: Mostafa Saleh <smostafa@xxxxxxxxxx>
> 
> To prepare for using TPIDRRO_EL0 to hold 'current' and repurposing
> SP_EL0 as an overflow stack pointer, eagerly switch both registers when
> entering and exiting the guest.
> 
> Signed-off-by: Mostafa Saleh <smostafa@xxxxxxxxxx>
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> ---
>  arch/arm64/include/asm/kvm_asm.h           | 10 ++++++++++
>  arch/arm64/kernel/asm-offsets.c            |  1 +
>  arch/arm64/kvm/hyp/entry.S                 | 12 ++++++++----
>  arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h |  2 --
>  4 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index e5b92ac09e69..1cfe9216a2ff 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -408,6 +408,16 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, u64 elr_virt,
>  	msr	sp_el0, \tmp
>  .endm
>  
> +.macro save_tpidrro_el0 ctxt, tmp
> +	mrs	\tmp,	tpidrro_el0
> +	str	\tmp,	[\ctxt, #CPU_TPIDRRO_EL0_OFFSET]
> +.endm
> +
> +.macro restore_tpidrro_el0 ctxt, tmp
> +	ldr	\tmp,	  [\ctxt, #CPU_TPIDRRO_EL0_OFFSET]
> +	msr	tpidrro_el0, \tmp
> +.endm
> +
>  #endif
>  
>  #endif /* __ARM_KVM_ASM_H__ */
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 6038ab3beb25..cb8448cc5f51 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -108,6 +108,7 @@ int main(void)
>    DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>    DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_cpu_context, regs));
>    DEFINE(CPU_ELR_EL2,		offsetof(struct kvm_cpu_context, sys_regs[ELR_EL2]));
> +  DEFINE(CPU_TPIDRRO_EL0_OFFSET, offsetof(struct kvm_cpu_context, sys_regs[TPIDRRO_EL0]));
>    DEFINE(CPU_RGSR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
>    DEFINE(CPU_GCR_EL1,		offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
>    DEFINE(CPU_APIAKEYLO_EL1,	offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index 308100ed25de..4c89931a6a92 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -30,8 +30,9 @@ SYM_FUNC_START(__guest_enter)
>  	// Store the hyp regs
>  	save_callee_saved_regs x1
>  
> -	// Save hyp's sp_el0
> +	// Save hyp's sp_el0 and tpidrro_el0
>  	save_sp_el0	x1, x2
> +	save_tpidrro_el0 x1, x2
>  
>  	// Now the hyp state is stored if we have a pending RAS SError it must
>  	// affect the host or hyp. If any asynchronous exception is pending we
> @@ -66,8 +67,9 @@ alternative_else_nop_endif
>  	// when this feature is enabled for kernel code.
>  	ptrauth_switch_to_guest x29, x0, x1, x2
>  
> -	// Restore the guest's sp_el0
> +	// Restore the guest's sp_el0 and tpidrro_el0
>  	restore_sp_el0 x29, x0
> +	restore_tpidrro_el0 x29, x0
>  
>  	// Restore guest regs x0-x17
>  	ldp	x0, x1,   [x29, #CPU_XREG_OFFSET(0)]
> @@ -146,8 +148,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>  	// Store the guest regs x18-x29, lr
>  	save_callee_saved_regs x1
>  
> -	// Store the guest's sp_el0
> +	// Store the guest's sp_el0 and tpidrro_el0
>  	save_sp_el0	x1, x2
> +	save_tpidrro_el0 x1, x2
>  
>  	adr_this_cpu x2, kvm_hyp_ctxt, x3
>  
> @@ -161,8 +164,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>  	// mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
>  	mte_switch_to_hyp x1, x2, x3
>  
> -	// Restore hyp's sp_el0
> +	// Restore hyp's sp_el0 and tpidrro_el0
>  	restore_sp_el0 x2, x3
> +	restore_tpidrro_el0 x2, x3

Reviewed-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>

>  
>  	// Now restore the hyp regs
>  	restore_callee_saved_regs x2
> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> index c382848d3194..b5f7ef8e6371 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> @@ -66,7 +66,6 @@ static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>  static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>  {
>  	ctxt_sys_reg(ctxt, TPIDR_EL0)	= read_sysreg(tpidr_el0);
> -	ctxt_sys_reg(ctxt, TPIDRRO_EL0)	= read_sysreg(tpidrro_el0);
>  }
>  
>  static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
> @@ -209,7 +208,6 @@ static inline void __sysreg_restore_common_state(struct kvm_cpu_context *ctxt)
>  static inline void __sysreg_restore_user_state(struct kvm_cpu_context *ctxt)
>  {
>  	write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL0),	tpidr_el0);
> -	write_sysreg(ctxt_sys_reg(ctxt, TPIDRRO_EL0),	tpidrro_el0);
>  }
>  
>  static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt,

-- 
Best regards,
Jinjie