Hi James, Little late in replying as some issue in my mail settings. On 1/31/19 9:52 PM, James Morse wrote: > 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. Ok, agree. > > There ought to be some justification for moving hcr/mdcr into the cpu_context in > the commit message. ohh I missed adding in commit. Just added in cover letter. > > > 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 at arm.com> > [ Move hcr to cpu_context, added __cpu_copy_hyp_conf()] >> Signed-off-by: Amit Daniel Kachhap <amit.kachhap at arm.com> > > (9c06602b1b92 is a good picked-at-random example for both of these) Thanks for the information. > > >> 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? yes one wrapper for each of them will do. > > 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!) Yes. Can be moved before. //Amit D > > > Thanks, > > James >
