Hi Amit, On 28/01/2019 06:58, Amit Daniel Kachhap wrote: > When restoring HCR_EL2 for the host, KVM uses HCR_HOST_VHE_FLAGS, which > is a constant value. This works today, as the host HCR_EL2 value is > always the same, but this will get in the way of supporting extensions > that require HCR_EL2 bits to be set conditionally for the host. > > To allow such features to work without KVM having to explicitly handle > every possible host feature combination, this patch has KVM save/restore > the host HCR when switching to/from a guest HCR. The saving of the > register is done once during cpu hypervisor initialization state and is > just restored after switch from guest. > > For fetching HCR_EL2 during kvm initialisation, a hyp call is made using > kvm_call_hyp and is helpful in NHVE case. > For the hyp TLB maintenance code, __tlb_switch_to_host_vhe() is updated > to toggle the TGE bit with a RMW sequence, as we already do in > __tlb_switch_to_guest_vhe(). > While at it, host MDCR_EL2 value is fetched in a similar way and restored > after every switch from host to guest. There should not be any change in > functionality due to this. Could this step be done as a separate subsequent patch? It would make review easier! The MDCR stuff would be a simplification if done second, done in one go like this its pretty noisy. There ought to be some justification for moving hcr/mdcr into the cpu_context in the commit message. If you're keeping Mark's 'Signed-off-by' its would be normal to keep Mark as the author in git. This shows up a an extra 'From:' when you post the patch, and gets picked up when the maintainer runs git-am. This patch has changed substantially from Mark's version: https://lkml.org/lkml/2017/11/27/675 If you keep the signed-off-by, could you add a [note] in the signed-off area with a terse summary. Something like: > Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> [ Move hcr to cpu_context, added __cpu_copy_hyp_conf()] > Signed-off-by: Amit Daniel Kachhap <amit.kachhap@xxxxxxx> (9c06602b1b92 is a good picked-at-random example for both of these) > diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h > index f5b79e9..2da6e43 100644 > --- a/arch/arm64/include/asm/kvm_asm.h > +++ b/arch/arm64/include/asm/kvm_asm.h > @@ -80,6 +80,8 @@ extern void __vgic_v3_init_lrs(void); > > extern u32 __kvm_get_mdcr_el2(void); > > +extern u64 __kvm_get_hcr_el2(void); Do we need these in separate helpers? For non-vhe this means two separate trips to EL2. Something like kvm_populate_host_context(void), and an __ version for the bit at EL2? We don't need to pass the host-context to EL2 as once kvm is loaded we can access host per-cpu variables at EL2 using __hyp_this_cpu_read(). This will save passing the vcpu around. > @@ -458,6 +457,25 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu, > > static inline void __cpu_init_stage2(void) {} > > +/** > + * __cpu_copy_hyp_conf - copy the boot hyp configuration registers > + * > + * It is called once per-cpu during CPU hyp initialisation. > + */ > +static inline void __cpu_copy_hyp_conf(void) > +{ > + kvm_cpu_context_t *host_cxt = this_cpu_ptr(&kvm_host_cpu_state); > + > + host_cxt->hcr_el2 = kvm_call_hyp(__kvm_get_hcr_el2); > + > + /* > + * Retrieve the initial value of mdcr_el2 so we can preserve > + * MDCR_EL2.HPMN which has presumably been set-up by some > + * knowledgeable bootcode. > + */ > + host_cxt->mdcr_el2 = kvm_call_hyp(__kvm_get_mdcr_el2); > +} Its strange to make this an inline in a header. kvm_arm_init_debug() is a static-inline for arch/arm, but a regular C function for arch/arm64. Can't we do the same? > diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c > index 68d6f7c..22c854a 100644 > --- a/arch/arm64/kvm/hyp/sysreg-sr.c > +++ b/arch/arm64/kvm/hyp/sysreg-sr.c > @@ -316,3 +316,14 @@ void __hyp_text __kvm_enable_ssbs(void) > "msr sctlr_el2, %0" > : "=&r" (tmp) : "L" (SCTLR_ELx_DSSBS)); > } > + > +/** > + * __read_hyp_hcr_el2 - Returns hcr_el2 register value > + * > + * This function acts as a function handler parameter for kvm_call_hyp and > + * may be called from EL1 exception level to fetch the register value. > + */ > +u64 __hyp_text __kvm_get_hcr_el2(void) > +{ > + return read_sysreg(hcr_el2); > +} While I'm all in favour of kernel-doc comments for functions, it may be over-kill in this case! > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > index 9e350fd3..2d65ada 100644 > --- a/virt/kvm/arm/arm.c > +++ b/virt/kvm/arm/arm.c > @@ -1327,10 +1327,10 @@ static void cpu_hyp_reinit(void) > else > cpu_init_hyp_mode(NULL); > > - kvm_arm_init_debug(); > - > if (vgic_present) > kvm_vgic_init_cpu_hardware(); > + > + __cpu_copy_hyp_conf(); > } Was there a reason to make this call later than it originally was? (kvm_vgic_init_cpu_hardware() doesn't use any of those values, so its fine, just curious!) Thanks, James _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
