Re: [PATCH v6 06/64] KVM: arm64: nv: Add nested virt VCPU primitives for vEL2 VCPU state
From: Alexandru Elisei <hidden>
Date: 2022-02-02 12:11:26
Also in:
kvm, kvmarm
Hi Marc, On Fri, Jan 28, 2022 at 12:18:14PM +0000, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
From: Christoffer Dall <redacted> When running a nested hypervisor we commonly have to figure out if the VCPU mode is running in the context of a guest hypervisor or guest guest, or just a normal guest. Add convenient primitives for this. Reviewed-by: Russell King (Oracle) <redacted> Signed-off-by: Christoffer Dall <redacted> Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/include/asm/kvm_emulate.h | 53 ++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+)diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h index d62405ce3e6d..ea9a130c4b6a 100644 --- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h@@ -178,6 +178,59 @@ static __always_inline void vcpu_set_reg(struct kvm_vcpu *vcpu, u8 reg_num, vcpu_gp_regs(vcpu)->regs[reg_num] = val; } +static inline bool vcpu_is_el2_ctxt(const struct kvm_cpu_context *ctxt) +{ + switch (ctxt->regs.pstate & (PSR_MODE32_BIT | PSR_MODE_MASK)) { + case PSR_MODE_EL2h: + case PSR_MODE_EL2t: + return true; + default: + return false; + } +} + +static inline bool vcpu_is_el2(const struct kvm_vcpu *vcpu) +{ + return vcpu_is_el2_ctxt(&vcpu->arch.ctxt); +} + +static inline bool __vcpu_el2_e2h_is_set(const struct kvm_cpu_context *ctxt) +{ + return ctxt_sys_reg(ctxt, HCR_EL2) & HCR_E2H; +} + +static inline bool vcpu_el2_e2h_is_set(const struct kvm_vcpu *vcpu) +{ + return __vcpu_el2_e2h_is_set(&vcpu->arch.ctxt); +} + +static inline bool __vcpu_el2_tge_is_set(const struct kvm_cpu_context *ctxt) +{ + return ctxt_sys_reg(ctxt, HCR_EL2) & HCR_TGE; +} + +static inline bool vcpu_el2_tge_is_set(const struct kvm_vcpu *vcpu) +{ + return __vcpu_el2_tge_is_set(&vcpu->arch.ctxt); +} + +static inline bool __is_hyp_ctxt(const struct kvm_cpu_context *ctxt) +{ + /* + * We are in a hypervisor context if the vcpu mode is EL2 or + * E2H and TGE bits are set. The latter means we are in the user space + * of the VHE kernel. ARMv8.1 ARM describes this as 'InHost' + */ + return vcpu_is_el2_ctxt(ctxt) || + (__vcpu_el2_e2h_is_set(ctxt) && __vcpu_el2_tge_is_set(ctxt)) || + WARN_ON(__vcpu_el2_tge_is_set(ctxt));
Why the WARN_ON? Wouldn't it be easy for a guest to flood the host's dmesg with
warnings by setting HCR_EL2.{E2H,TGE} = {0, 1} and then repeatedly accessing EL2
registers (for example)?
+} + +static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu)
When KVM boots at EL2 and FEAT_VHE is not implemented it prints to dmesg: [ 1.352302] kvm [1]: Hyp mode initialized successfully I take it in that context "Hyp" means "EL2 NVHE", because when E2H,TGE are set the message changes to: [ 0.037683] kvm [1]: VHE mode initialized successfully In this file, in the function is_kernel_in_hyp_mode(), "hyp" actually means that the exception level is EL2. In kvm/arm.c, "hyp" also means EL2 (or maybe EL2 NVHE?). Wouldn't it be nice to avoid having "hyp" mean yet another thing and replace it with "hypervisor" in these two functions? Thanks, Alex
+{
+ return __is_hyp_ctxt(&vcpu->arch.ctxt);
+}
+
/*
* The layout of SPSR for an AArch32 state is different when observed from an
* AArch64 SPSR_ELx or an AArch32 SPSR_*. This function generates the AArch32
--
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