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Date: Mon, 2 Jul 2018 14:32:02 +0100
From: Marc Zyngier <marc.zyngier@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
kvmarm@...ts.cs.columbia.edu, james.morse@....com,
cdall@...nel.org, eric.auger@...hat.com, julien.grall@....com,
will.deacon@....com, catalin.marinas@....com,
punit.agrawal@....com, qemu-devel@...gnu.org
Subject: Re: [PATCH v3 16/20] kvm: arm64: Switch to per VM IPA limit
On 29/06/18 12:15, Suzuki K Poulose wrote:
> Now that we can manage the stage2 page table per VM, switch the
> configuration details to per VM instance. We keep track of the
> IPA bits, number of page table levels and the VTCR bits (which
> depends on the IPA and the number of levels). While at it, remove
> unused pgd_lock field from kvm_arch for arm64.
>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Christoffer Dall <cdall@...nel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> arch/arm64/include/asm/kvm_host.h | 14 ++++++++++++--
> arch/arm64/include/asm/kvm_hyp.h | 3 +--
> arch/arm64/include/asm/kvm_mmu.h | 20 ++++++++++++++++++--
> arch/arm64/include/asm/stage2_pgtable.h | 1 -
> virt/kvm/arm/mmu.c | 4 ++++
> 5 files changed, 35 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 328f472..9a15860 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -61,13 +61,23 @@ struct kvm_arch {
> u64 vmid_gen;
> u32 vmid;
>
> - /* 1-level 2nd stage table and lock */
> - spinlock_t pgd_lock;
> + /* stage-2 page table */
> pgd_t *pgd;
>
> /* VTTBR value associated with above pgd and vmid */
> u64 vttbr;
>
> + /* Private bits of VTCR_EL2 for this VM */
> + u64 vtcr_private;
As I said in another email, this should become a full VTCR_EL2 copy.
> + /* Size of the PA size for this guest */
> + u8 phys_shift;
> + /*
> + * Number of levels in page table. We could always calculate
> + * it from phys_shift above. We cache it for faster switches
> + * in stage2 page table helpers.
> + */
> + u8 s2_levels;
And these two fields feel like they should be derived from the VTCR
itself, instead of being there on their own. Any chance you could look
into this?
> +
> /* The last vcpu id that ran on each physical CPU */
> int __percpu *last_vcpu_ran;
>
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index 3e8052d1..699f678 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -166,8 +166,7 @@ static __always_inline void __hyp_text __load_guest_stage2(struct kvm *kvm)
> u64 vtcr = read_sysreg(vtcr_el2);
>
> vtcr &= ~VTCR_EL2_PRIVATE_MASK;
> - vtcr |= VTCR_EL2_SL0(kvm_stage2_levels(kvm)) |
> - VTCR_EL2_T0SZ(kvm_phys_shift(kvm));
> + vtcr |= kvm->arch.vtcr_private;
> write_sysreg(vtcr, vtcr_el2);
> write_sysreg(kvm->arch.vttbr, vttbr_el2);
> }
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index f3fb05a3..a291cdc 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -143,9 +143,10 @@ static inline unsigned long __kern_hyp_va(unsigned long v)
> */
> #define KVM_PHYS_SHIFT (40)
>
> -#define kvm_phys_shift(kvm) KVM_PHYS_SHIFT
> +#define kvm_phys_shift(kvm) (kvm->arch.phys_shift)
> #define kvm_phys_size(kvm) (_AC(1, ULL) << kvm_phys_shift(kvm))
> #define kvm_phys_mask(kvm) (kvm_phys_size(kvm) - _AC(1, ULL))
> +#define kvm_stage2_levels(kvm) (kvm->arch.s2_levels)
>
> static inline bool kvm_page_empty(void *ptr)
> {
> @@ -528,6 +529,18 @@ static inline u64 kvm_vttbr_baddr_mask(struct kvm *kvm)
>
> static inline void *stage2_alloc_pgd(struct kvm *kvm)
> {
> + u32 ipa, lvls;
> +
> + /*
> + * Stage2 page table can support concatenation of (upto 16) tables
> + * at the entry level, thereby reducing the number of levels.
> + */
> + ipa = kvm_phys_shift(kvm);
> + lvls = stage2_pt_levels(ipa);
> +
> + kvm->arch.s2_levels = lvls;
> + kvm->arch.vtcr_private = VTCR_EL2_SL0(lvls) | TCR_T0SZ(ipa);
> +
> return alloc_pages_exact(stage2_pgd_size(kvm),
> GFP_KERNEL | __GFP_ZERO);
> }
> @@ -537,7 +550,10 @@ static inline u32 kvm_get_ipa_limit(void)
> return KVM_PHYS_SHIFT;
> }
>
> -static inline void kvm_config_stage2(struct kvm *kvm, u32 ipa_shift) {}
> +static inline void kvm_config_stage2(struct kvm *kvm, u32 ipa_shift)
> +{
> + kvm->arch.phys_shift = ipa_shift;
> +}
>
> #endif /* __ASSEMBLY__ */
> #endif /* __ARM64_KVM_MMU_H__ */
> diff --git a/arch/arm64/include/asm/stage2_pgtable.h b/arch/arm64/include/asm/stage2_pgtable.h
> index ffc37cc..91d7936 100644
> --- a/arch/arm64/include/asm/stage2_pgtable.h
> +++ b/arch/arm64/include/asm/stage2_pgtable.h
> @@ -65,7 +65,6 @@
> #define __s2_pgd_ptrs(pa, lvls) (1 << ((pa) - pt_levels_pgdir_shift((lvls))))
> #define __s2_pgd_size(pa, lvls) (__s2_pgd_ptrs((pa), (lvls)) * sizeof(pgd_t))
>
> -#define kvm_stage2_levels(kvm) stage2_pt_levels(kvm_phys_shift(kvm))
> #define stage2_pgdir_shift(kvm) \
> pt_levels_pgdir_shift(kvm_stage2_levels(kvm))
> #define stage2_pgdir_size(kvm) (_AC(1, UL) << stage2_pgdir_shift((kvm)))
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index a339e00..d7822e1 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -867,6 +867,10 @@ int kvm_alloc_stage2_pgd(struct kvm *kvm)
> return -EINVAL;
> }
>
> + /* Make sure we have the stage2 configured for this VM */
> + if (WARN_ON(!kvm_phys_shift(kvm)))
Can this be triggered from userspace?
> + return -EINVAL;
> +
> /* Allocate the HW PGD, making sure that each page gets its own refcount */
> pgd = stage2_alloc_pgd(kvm);
> if (!pgd)
>
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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