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SubjectRe: [PATCH v3 13/20] kvm: arm64: Configure VTCR per VM
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On 29/06/18 12:15, Suzuki K Poulose wrote:
> We set VTCR_EL2 very early during the stage2 init and don't
> touch it ever. This is fine as we had a fixed IPA size. This
> patch changes the behavior to set the VTCR for a given VM,
> depending on its stage2 table. The common configuration for
> VTCR is still performed during the early init as we have to
> retain the hardware access flag update bits (VTCR_EL2_HA)
> per CPU (as they are only set for the CPUs which are capabile).

capable

> The bits defining the number of levels in the page table (SL0)
> and and the size of the Input address to the translation (T0SZ)
> are programmed for each VM upon entry to the guest.
>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Christoffer Dall <cdall@kernel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> Change since V2:
> - Load VTCR for TLB operations
> ---
> arch/arm64/include/asm/kvm_arm.h | 19 +++++++++----------
> arch/arm64/include/asm/kvm_asm.h | 2 +-
> arch/arm64/include/asm/kvm_host.h | 9 ++++++---
> arch/arm64/include/asm/kvm_hyp.h | 11 +++++++++++
> arch/arm64/kvm/hyp/s2-setup.c | 17 +----------------
> 5 files changed, 28 insertions(+), 30 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 11a7db0..b02c316 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -120,9 +120,7 @@
> #define VTCR_EL2_IRGN0_WBWA TCR_IRGN0_WBWA
> #define VTCR_EL2_SL0_SHIFT 6
> #define VTCR_EL2_SL0_MASK (3 << VTCR_EL2_SL0_SHIFT)
> -#define VTCR_EL2_SL0_LVL1 (1 << VTCR_EL2_SL0_SHIFT)
> #define VTCR_EL2_T0SZ_MASK 0x3f
> -#define VTCR_EL2_T0SZ_40B 24
> #define VTCR_EL2_VS_SHIFT 19
> #define VTCR_EL2_VS_8BIT (0 << VTCR_EL2_VS_SHIFT)
> #define VTCR_EL2_VS_16BIT (1 << VTCR_EL2_VS_SHIFT)
> @@ -137,43 +135,44 @@
> * VTCR_EL2.PS is extracted from ID_AA64MMFR0_EL1.PARange at boot time
> * (see hyp-init.S).
> *
> + * VTCR_EL2.SL0 and T0SZ are configured per VM at runtime before switching to
> + * the VM.
> + *
> * Note that when using 4K pages, we concatenate two first level page tables
> * together. With 16K pages, we concatenate 16 first level page tables.
> *
> */
>
> -#define VTCR_EL2_T0SZ_IPA VTCR_EL2_T0SZ_40B
> #define VTCR_EL2_COMMON_BITS (VTCR_EL2_SH0_INNER | VTCR_EL2_ORGN0_WBWA | \
> VTCR_EL2_IRGN0_WBWA | VTCR_EL2_RES1)
> +#define VTCR_EL2_PRIVATE_MASK (VTCR_EL2_SL0_MASK | VTCR_EL2_T0SZ_MASK)

What does "private" mean here? It really is the IPA configuration, so
I'd rather have a naming that reflects that.

> #ifdef CONFIG_ARM64_64K_PAGES
> /*
> * Stage2 translation configuration:
> * 64kB pages (TG0 = 1)
> - * 2 level page tables (SL = 1)
> */
> -#define VTCR_EL2_TGRAN_FLAGS (VTCR_EL2_TG0_64K | VTCR_EL2_SL0_LVL1)
> +#define VTCR_EL2_TGRAN VTCR_EL2_TG0_64K
> #define VTCR_EL2_TGRAN_SL0_BASE 3UL
>
> #elif defined(CONFIG_ARM64_16K_PAGES)
> /*
> * Stage2 translation configuration:
> * 16kB pages (TG0 = 2)
> - * 2 level page tables (SL = 1)
> */
> -#define VTCR_EL2_TGRAN_FLAGS (VTCR_EL2_TG0_16K | VTCR_EL2_SL0_LVL1)
> +#define VTCR_EL2_TGRAN VTCR_EL2_TG0_16K
> #define VTCR_EL2_TGRAN_SL0_BASE 3UL
> #else /* 4K */
> /*
> * Stage2 translation configuration:
> * 4kB pages (TG0 = 0)
> - * 3 level page tables (SL = 1)
> */
> -#define VTCR_EL2_TGRAN_FLAGS (VTCR_EL2_TG0_4K | VTCR_EL2_SL0_LVL1)
> +#define VTCR_EL2_TGRAN VTCR_EL2_TG0_4K
> #define VTCR_EL2_TGRAN_SL0_BASE 2UL
> #endif
>
> -#define VTCR_EL2_FLAGS (VTCR_EL2_COMMON_BITS | VTCR_EL2_TGRAN_FLAGS)
> +#define VTCR_EL2_FLAGS (VTCR_EL2_COMMON_BITS | VTCR_EL2_TGRAN)
> +
> /*
> * VTCR_EL2:SL0 indicates the entry level for Stage2 translation.
> * Interestingly, it depends on the page size.
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 102b5a5..91372eb 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -72,7 +72,7 @@ extern void __vgic_v3_init_lrs(void);
>
> extern u32 __kvm_get_mdcr_el2(void);
>
> -extern u32 __init_stage2_translation(void);
> +extern void __init_stage2_translation(void);
>
> /* Home-grown __this_cpu_{ptr,read} variants that always work at HYP */
> #define __hyp_this_cpu_ptr(sym) \
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index fe8777b..328f472 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -442,10 +442,13 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
>
> static inline void __cpu_init_stage2(void)
> {
> - u32 parange = kvm_call_hyp(__init_stage2_translation);
> + u32 ps;
>
> - WARN_ONCE(parange < 40,
> - "PARange is %d bits, unsupported configuration!", parange);
> + kvm_call_hyp(__init_stage2_translation);
> + /* Sanity check for minimum IPA size support */
> + ps = id_aa64mmfr0_parange_to_phys_shift(read_sysreg(id_aa64mmfr0_el1) & 0x7);
> + WARN_ONCE(ps < 40,
> + "PARange is %d bits, unsupported configuration!", ps);
> }
>
> /* Guest/host FPSIMD coordination helpers */
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index 82f9994..3e8052d1 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -20,6 +20,7 @@
>
> #include <linux/compiler.h>
> #include <linux/kvm_host.h>
> +#include <asm/kvm_mmu.h>
> #include <asm/sysreg.h>
>
> #define __hyp_text __section(.hyp.text) notrace
> @@ -158,6 +159,16 @@ void __noreturn __hyp_do_panic(unsigned long, ...);
> /* Must be called from hyp code running at EL2 */
> static __always_inline void __hyp_text __load_guest_stage2(struct kvm *kvm)
> {
> + /*
> + * Configure the VTCR translation control bits
> + * for this VM.
> + */
> + 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));
> + write_sysreg(vtcr, vtcr_el2);

Can't we generate the whole vtcr value in one go, without reading it
back? Specially given that on patch 16, you're actually switching to a
per-VM variable, and it would make a lot of sense to start with that here.

> write_sysreg(kvm->arch.vttbr, vttbr_el2);
> }
>
> diff --git a/arch/arm64/kvm/hyp/s2-setup.c b/arch/arm64/kvm/hyp/s2-setup.c
> index 81094f1..6567315 100644
> --- a/arch/arm64/kvm/hyp/s2-setup.c
> +++ b/arch/arm64/kvm/hyp/s2-setup.c
> @@ -19,13 +19,11 @@
> #include <asm/kvm_arm.h>
> #include <asm/kvm_asm.h>
> #include <asm/kvm_hyp.h>
> -#include <asm/cpufeature.h>
>
> -u32 __hyp_text __init_stage2_translation(void)
> +void __hyp_text __init_stage2_translation(void)
> {
> u64 val = VTCR_EL2_FLAGS;
> u64 parange;
> - u32 phys_shift;
> u64 tmp;
>
> /*
> @@ -38,17 +36,6 @@ u32 __hyp_text __init_stage2_translation(void)
> parange = ID_AA64MMFR0_PARANGE_MAX;
> val |= parange << VTCR_EL2_PS_SHIFT;
>
> - /* Compute the actual PARange... */
> - phys_shift = id_aa64mmfr0_parange_to_phys_shift(parange);
> -
> - /*
> - * ... and clamp it to 40 bits, unless we have some braindead
> - * HW that implements less than that. In all cases, we'll
> - * return that value for the rest of the kernel to decide what
> - * to do.
> - */
> - val |= VTCR_EL2_T0SZ(phys_shift > 40 ? 40 : phys_shift);
> -
> /*
> * Check the availability of Hardware Access Flag / Dirty Bit
> * Management in ID_AA64MMFR1_EL1 and enable the feature in VTCR_EL2.
> @@ -67,6 +54,4 @@ u32 __hyp_text __init_stage2_translation(void)
> VTCR_EL2_VS_8BIT;
>
> write_sysreg(val, vtcr_el2);

And then most of the code here could run on a per-VM basis.

> -
> - return phys_shift;
> }
>

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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