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Message-ID: <551135AE.1080401@arm.com>
Date: Tue, 24 Mar 2015 10:00:14 +0000
From: Marc Zyngier <marc.zyngier@....com>
To: AKASHI Takahiro <takahiro.akashi@...aro.org>,
Catalin Marinas <Catalin.Marinas@....com>,
Will Deacon <Will.Deacon@....com>,
Mark Rutland <Mark.Rutland@....com>
CC: "christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
"geoff@...radead.org" <geoff@...radead.org>,
"broonie@...nel.org" <broonie@...nel.org>,
"david.griego@...aro.org" <david.griego@...aro.org>,
"freddy77@...il.com" <freddy77@...il.com>,
"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 1/4] arm64: kvm: add a cpu tear-down function
Hi Takahiro,
On 23/03/15 11:53, AKASHI Takahiro wrote:
> Cpu must be put back into its initial state, at least, in the
> following cases in order to shutdown the system and/or re-initialize cpus
> later on:
> 1) kexec/kdump
> 2) cpu hotplug (offline)
> 3) removing kvm as a module
>
> To address those issues in later patches, this patch adds a tear-down
> function, kvm_cpu_reset(), that disables D-cache & MMU and restore a vector
> table to the initial stub at EL2.
Thanks for having a look at this.
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
> ---
> arch/arm/kvm/arm.c | 18 ++++++++++++++++
> arch/arm/kvm/mmu.c | 16 +++++++++++++++
> arch/arm64/include/asm/kvm_asm.h | 3 +++
> arch/arm64/include/asm/kvm_host.h | 10 +++++++++
> arch/arm64/include/asm/kvm_mmu.h | 3 +++
> arch/arm64/include/asm/virt.h | 11 ++++++++++
> arch/arm64/kvm/hyp-init.S | 41 +++++++++++++++++++++++++++++++++++++
> arch/arm64/kvm/hyp.S | 29 ++++++++++++++++++++++----
> 8 files changed, 127 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 5560f74..35c8bc0 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -897,6 +897,24 @@ static void cpu_init_hyp_mode(void *dummy)
> __cpu_init_hyp_mode(boot_pgd_ptr, pgd_ptr, hyp_stack_ptr, vector_ptr);
> }
>
> +void kvm_cpu_reset(void *dummy)
Given that the notifier introduced in patch #2 lives in the same file,
this could be made static, couldn't it?
> +{
> + phys_addr_t boot_pgd_ptr;
> + phys_addr_t phys_idmap_start;
> + unsigned long reset_func;
> + unsigned long vector_ptr;
> +
> + if (__hyp_get_vectors() == hyp_default_vectors)
> + return;
> +
> + reset_func = kvm_reset_func_entry();
> + boot_pgd_ptr = kvm_mmu_get_boot_httbr();
> + phys_idmap_start = kvm_get_idmap_start();
> + vector_ptr = kvm_get_stub_vectors();
Isn't that hyp_default_vectors already?
> + __cpu_reset_hyp_mode(reset_func,
> + boot_pgd_ptr, phys_idmap_start, vector_ptr);
> +}
> +
> static int hyp_init_cpu_notify(struct notifier_block *self,
> unsigned long action, void *cpu)
> {
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 3e6859b..428f41c 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -1490,6 +1490,22 @@ phys_addr_t kvm_get_idmap_vector(void)
> return hyp_idmap_vector;
> }
>
> +phys_addr_t kvm_get_idmap_start(void)
> +{
> + return hyp_idmap_start;
> +}
> +
> +phys_addr_t kvm_get_stub_vectors(void)
> +{
> + return virt_to_phys(__hyp_stub_vectors);
> +}
As Geoff already mentioned, this doesn't belong in KVM. But I don't
think you need it, as explained above.
> +
> +unsigned long kvm_reset_func_entry(void)
> +{
> + /* VA of __kvm_hyp_reset in trampline code */
> + return TRAMPOLINE_VA + (__kvm_hyp_reset - __hyp_idmap_text_start);
> +}
If you need to compute addresses in the trampoline page, it would be
better to have a generic macro that takes a kernel VA, and turns it into
a trampoline VA.
> +
> int kvm_mmu_init(void)
> {
> int err;
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 4f7310f..97ee2fc 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -116,8 +116,11 @@
> struct kvm;
> struct kvm_vcpu;
>
> +extern char __hyp_stub_vectors[];
Not a KVM thing (for the same reason).
> +
> extern char __kvm_hyp_init[];
> extern char __kvm_hyp_init_end[];
> +extern char __kvm_hyp_reset[];
>
> extern char __kvm_hyp_vector[];
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 8ac3c70..97f88fe 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -199,6 +199,7 @@ struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
> struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void);
>
> u64 kvm_call_hyp(void *hypfn, ...);
> +void kvm_call_reset(unsigned long reset_func, ...);
You seem to have a single call signature for this function, and have
defined all the parameters below. You can drop the variadic aspect.
> void force_vm_exit(const cpumask_t *mask);
> void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>
> @@ -223,6 +224,15 @@ static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
> hyp_stack_ptr, vector_ptr);
> }
>
> +static inline void __cpu_reset_hyp_mode(unsigned long reset_func,
> + phys_addr_t boot_pgd_ptr,
> + phys_addr_t phys_idmap_start,
> + unsigned long stub_vector_ptr)
> +{
> + kvm_call_reset(reset_func, boot_pgd_ptr,
> + phys_idmap_start, stub_vector_ptr);
> +}
> +
> struct vgic_sr_vectors {
> void *save_vgic;
> void *restore_vgic;
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 6458b53..36be582 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -96,6 +96,9 @@ void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu);
> phys_addr_t kvm_mmu_get_httbr(void);
> phys_addr_t kvm_mmu_get_boot_httbr(void);
> phys_addr_t kvm_get_idmap_vector(void);
> +phys_addr_t kvm_get_idmap_start(void);
> +phys_addr_t kvm_get_stub_vectors(void);
> +unsigned long kvm_reset_func_entry(void);
> int kvm_mmu_init(void);
> void kvm_clear_hyp_idmap(void);
>
> diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
> index 3070096..7fcd087 100644
> --- a/arch/arm64/include/asm/virt.h
> +++ b/arch/arm64/include/asm/virt.h
> @@ -61,6 +61,17 @@
> #define BOOT_CPU_MODE_EL1 (0xe11)
> #define BOOT_CPU_MODE_EL2 (0xe12)
>
> +/*
> + * HVC_RESET - Reset cpu in EL2 to initial state.
> + *
> + * @x0: entry address in trampoline code in va
> + * @x1: identical mapping page table in pa
> + * @x2: start address of identical mapping in pa
> + * @x3: initial stub vector in pa
> + */
> +
> +#define HVC_RESET 5
> +
> #ifndef __ASSEMBLY__
>
> /*
> diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
> index c319116..ca7e6bf 100644
> --- a/arch/arm64/kvm/hyp-init.S
> +++ b/arch/arm64/kvm/hyp-init.S
> @@ -115,6 +115,47 @@ target: /* We're now in the trampoline code, switch page tables */
> eret
> ENDPROC(__kvm_hyp_init)
>
> + /*
> + * x0: HYP boot pgd
> + * x1: HYP phys_idmap_start
> + * x2: HYP stub vectors
> + */
> +ENTRY(__kvm_hyp_reset)
> + /* We're in trampoline code in VA */
> + /* Invalidate the old TLBs */
> + tlbi alle2
> + dsb sy
Invalidating the TLBs before switching TTBR0_EL2 is unlikely to have the
effect you want.
> + /* Switch back to boot page tables */
> + msr ttbr0_el2, x0
> + isb
This is the place where you want TLBI to occur.
> + /* Branch into PA space */
> + adr x0, 1f
> + bfi x1, x0, #0, #PAGE_SHIFT
> + br x1
> +
> + /* We're now in idmap */
> +1: /* Invalidate the old TLBs again */
> + tlbi alle2
> + dsb sy
See? This is the only TLBI that actually makes sense. Now, given that
you are actually disabling the MMU, I'm not sure these TBLIs make much
sense.
> + /* Disable MMU */
> + mrs x0, sctlr_el2
> + and x1, x0, #SCTLR_EL2_EE
> + orr x0, x0, x1 // preserve endianness of EL2
> + ldr x1, =SCTLR_EL2_FLAGS
> + eor x1, x1, xzr
> + bic x0, x0, x1 // Clear SCTL_M and etc
> + msr sctlr_el2, x0
> + isb
> +
> + /* Switch back to stub vectors */
> + msr vbar_el2, x2
> +
> + eret
> +ENDPROC(__kvm_hyp_reset)
> +
> .ltorg
>
> .popsection
> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> index fd085ec..aee75f9 100644
> --- a/arch/arm64/kvm/hyp.S
> +++ b/arch/arm64/kvm/hyp.S
> @@ -1136,6 +1136,11 @@ ENTRY(kvm_call_hyp)
> ret
> ENDPROC(kvm_call_hyp)
>
> +ENTRY(kvm_call_reset)
> + hvc #HVC_RESET
> + ret
> +ENDPROC(kvm_call_reset)
> +
> .macro invalid_vector label, target
> .align 2
> \label:
> @@ -1179,10 +1184,10 @@ el1_sync: // Guest trapped into EL2
> cmp x18, #HVC_GET_VECTORS
> b.ne 1f
> mrs x0, vbar_el2
> - b 2f
> -
> -1: /* Default to HVC_CALL_HYP. */
> + b 3f
>
> +1: cmp x18, #HVC_CALL_HYP
> + b.ne 2f
> push lr, xzr
>
> /*
> @@ -1196,7 +1201,23 @@ el1_sync: // Guest trapped into EL2
> blr lr
>
> pop lr, xzr
> -2: eret
> + b 3f
> +
> + /*
> + * shuffle the parameters and jump into trampline code.
> + */
> +2: cmp x18, #HVC_RESET
> + b.ne 3f
> +
> + mov x18, x0
> + mov x0, x1
> + mov x1, x2
> + mov x2, x3
> + mov x3, x4
> + br x18
I'd rather move the shuffling of the registers before the HVC call.
> + /* not reach here */
> +
> +3: eret
>
> el1_trap:
> /*
>
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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