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SubjectRe: [PATCH] arm64: KVM: VHE: save and restore some PSTATE bits
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CC Catalin


On 2017/9/6 2:58, gengdongjiu wrote:
> when exit from guest, some host PSTATE bits may be lost, such as
> PSTATE.PAN or PSTATE.UAO. It is because host and hypervisor all run
> in the EL2, host PSTATE value cannot be saved and restored via
> SPSR_EL2. So if guest has changed the PSTATE, host continues with
> a wrong value guest has set.
>
> Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
> Signed-off-by: Haibin Zhang <zhanghaibin7@huawei.com>
> ---
> arch/arm64/include/asm/kvm_host.h | 8 +++++++
> arch/arm64/include/asm/kvm_hyp.h | 2 ++
> arch/arm64/include/asm/sysreg.h | 23 +++++++++++++++++++
> arch/arm64/kvm/hyp/entry.S | 2 --
> arch/arm64/kvm/hyp/switch.c | 24 ++++++++++++++++++--
> arch/arm64/kvm/hyp/sysreg-sr.c | 48 ++++++++++++++++++++++++++++++++++++---
> 6 files changed, 100 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index e923b58..cba7d3e 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -193,6 +193,12 @@ struct kvm_cpu_context {
> };
> };
>
> +struct kvm_cpu_host_pstate {
> + u64 daif;
> + u64 uao;
> + u64 pan;
> +};
> +
> typedef struct kvm_cpu_context kvm_cpu_context_t;
>
> struct kvm_vcpu_arch {
> @@ -227,6 +233,8 @@ struct kvm_vcpu_arch {
>
> /* Pointer to host CPU context */
> kvm_cpu_context_t *host_cpu_context;
> + /* Host PSTATE value */
> + struct kvm_cpu_host_pstate host_pstate;
> struct {
> /* {Break,watch}point registers */
> struct kvm_guest_debug_arch regs;
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index 4572a9b..a75587a 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -134,6 +134,8 @@
>
> void __sysreg_save_host_state(struct kvm_cpu_context *ctxt);
> void __sysreg_restore_host_state(struct kvm_cpu_context *ctxt);
> +void __sysreg_save_host_pstate(struct kvm_vcpu *vcpu);
> +void __sysreg_restore_host_pstate(struct kvm_vcpu *vcpu);
> void __sysreg_save_guest_state(struct kvm_cpu_context *ctxt);
> void __sysreg_restore_guest_state(struct kvm_cpu_context *ctxt);
> void __sysreg32_save_state(struct kvm_vcpu *vcpu);
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 248339e..efdcf40 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -295,6 +295,29 @@
> #define SYS_ICH_LR14_EL2 __SYS__LR8_EL2(6)
> #define SYS_ICH_LR15_EL2 __SYS__LR8_EL2(7)
>
> +#define REG_PSTATE_PAN sys_reg(3, 0, 4, 2, 3)
> +#define REG_PSTATE_UAO sys_reg(3, 0, 4, 2, 4)
> +
> +#define GET_PSTATE_PAN \
> + ({ \
> + u64 reg; \
> + asm volatile(ALTERNATIVE("mov %0, #0", \
> + "mrs_s %0, " __stringify(REG_PSTATE_PAN),\
> + ARM64_HAS_PAN)\
> + : "=r" (reg));\
> + reg; \
> + })
> +
> +#define GET_PSTATE_UAO \
> + ({ \
> + u64 reg; \
> + asm volatile(ALTERNATIVE("mov %0, #0",\
> + "mrs_s %0, " __stringify(REG_PSTATE_UAO),\
> + ARM64_HAS_UAO)\
> + : "=r" (reg));\
> + reg; \
> + })
> +
> /* Common SCTLR_ELx flags. */
> #define SCTLR_ELx_EE (1 << 25)
> #define SCTLR_ELx_I (1 << 12)
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index 12ee62d..7662ef5 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -96,8 +96,6 @@ ENTRY(__guest_exit)
>
> add x1, x1, #VCPU_CONTEXT
>
> - ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
> -
> // Store the guest regs x2 and x3
> stp x2, x3, [x1, #CPU_XREG_OFFSET(2)]
>
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 945e79c..9b380a1 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -278,6 +278,26 @@ static void __hyp_text __skip_instr(struct kvm_vcpu *vcpu)
> write_sysreg_el2(*vcpu_pc(vcpu), elr);
> }
>
> +static void __hyp_text __save_host_state(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_cpu_context *host_ctxt;
> +
> + host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> +
> + __sysreg_save_host_state(host_ctxt);
> + __sysreg_save_host_pstate(vcpu);
> +}
> +
> +static void __hyp_text __restore_host_state(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_cpu_context *host_ctxt;
> +
> + host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> +
> + __sysreg_restore_host_state(host_ctxt);
> + __sysreg_restore_host_pstate(vcpu);
> +}
> +
> int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> {
> struct kvm_cpu_context *host_ctxt;
> @@ -291,7 +311,7 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> guest_ctxt = &vcpu->arch.ctxt;
>
> - __sysreg_save_host_state(host_ctxt);
> + __save_host_state(vcpu);
> __debug_cond_save_host_state(vcpu);
>
> __activate_traps(vcpu);
> @@ -374,7 +394,7 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> __deactivate_traps(vcpu);
> __deactivate_vm(vcpu);
>
> - __sysreg_restore_host_state(host_ctxt);
> + __restore_host_state(vcpu);
>
> if (fp_enabled) {
> __fpsimd_save_state(&guest_ctxt->gp_regs.fp_regs);
> diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index 9341376..ea8f437 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -22,7 +22,11 @@
> #include <asm/kvm_hyp.h>
>
> /* Yes, this does nothing, on purpose */
> -static void __hyp_text __sysreg_do_nothing(struct kvm_cpu_context *ctxt) { }
> +static void __hyp_text __sysreg_do_nothing_state(struct kvm_cpu_context *ctxt)
> +{ }
> +static void __hyp_text __sysreg_do_nothing_pstate(struct kvm_vcpu *vcpu)
> +{ }
> +
>
> /*
> * Non-VHE: Both host and guest must save everything.
> @@ -69,7 +73,7 @@ static void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt)
> }
>
> static hyp_alternate_select(__sysreg_call_save_host_state,
> - __sysreg_save_state, __sysreg_do_nothing,
> + __sysreg_save_state, __sysreg_do_nothing_state,
> ARM64_HAS_VIRT_HOST_EXTN);
>
> void __hyp_text __sysreg_save_host_state(struct kvm_cpu_context *ctxt)
> @@ -122,7 +126,7 @@ static void __hyp_text __sysreg_restore_state(struct kvm_cpu_context *ctxt)
> }
>
> static hyp_alternate_select(__sysreg_call_restore_host_state,
> - __sysreg_restore_state, __sysreg_do_nothing,
> + __sysreg_restore_state, __sysreg_do_nothing_state,
> ARM64_HAS_VIRT_HOST_EXTN);
>
> void __hyp_text __sysreg_restore_host_state(struct kvm_cpu_context *ctxt)
> @@ -137,6 +141,44 @@ void __hyp_text __sysreg_restore_guest_state(struct kvm_cpu_context *ctxt)
> __sysreg_restore_common_state(ctxt);
> }
>
> +static void __hyp_text __sysreg_save_pstate(struct kvm_vcpu *vcpu)
> +{
> + vcpu->arch.host_pstate.daif = read_sysreg(daif);
> + vcpu->arch.host_pstate.pan = GET_PSTATE_PAN;
> + vcpu->arch.host_pstate.uao = GET_PSTATE_UAO;
> +}
> +
> +static hyp_alternate_select(__sysreg_call_save_host_pstate,
> + __sysreg_save_pstate, __sysreg_do_nothing_pstate,
> + ARM64_HAS_VIRT_HOST_EXTN);
> +
> +void __hyp_text __sysreg_save_host_pstate(struct kvm_vcpu *vcpu)
> +{
> + __sysreg_call_save_host_pstate()(vcpu);
> +}
> +
> +static void __hyp_text __sysreg_restore_pstate(struct kvm_vcpu *vcpu)
> +{
> + u8 value = !!(vcpu->arch.host_pstate.pan);
> +
> + write_sysreg(vcpu->arch.host_pstate.daif, daif);
> + asm(ALTERNATIVE("nop", SET_PSTATE_PAN(value), ARM64_HAS_PAN,
> + CONFIG_ARM64_PAN));
> +
> + value = !!(vcpu->arch.host_pstate.uao);
> + asm(ALTERNATIVE("nop", SET_PSTATE_UAO(value), ARM64_HAS_UAO,
> + CONFIG_ARM64_UAO));
> +}
> +
> +static hyp_alternate_select(__sysreg_call_restore_host_pstate,
> + __sysreg_restore_pstate, __sysreg_do_nothing_pstate,
> + ARM64_HAS_VIRT_HOST_EXTN);
> +
> +void __hyp_text __sysreg_restore_host_pstate(struct kvm_vcpu *vcpu)
> +{
> + __sysreg_call_restore_host_pstate()(vcpu);
> +}
> +
> void __hyp_text __sysreg32_save_state(struct kvm_vcpu *vcpu)
> {
> u64 *spsr, *sysreg;
>

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