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References: <20220314200148.2695206-1-kaleshsingh@google.com> <20220314200148.2695206-2-kaleshsingh@google.com>
In-Reply-To: <20220314200148.2695206-2-kaleshsingh@google.com>
From:   Fuad Tabba <tabba@google.com>
Date:   Tue, 29 Mar 2022 09:50:38 +0100
Message-ID: <CA+EHjTxx7RoLods=9xz4RZF3FSFZdH+7kwcHCurpUqAD+mtgzA@mail.gmail.com>
Subject: Re: [PATCH v6 1/8] KVM: arm64: Introduce hyp_alloc_private_va_range()
To:     Kalesh Singh <kaleshsingh@google.com>
Cc:     will@kernel.org, maz@kernel.org, qperret@google.com,
        surenb@google.com, kernel-team@android.com,
        James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Mark Brown <broonie@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Peter Collingbourne <pcc@google.com>,
        "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>,
        Stephen Boyd <swboyd@chromium.org>,
        Andrew Scull <ascull@google.com>,
        Andrew Jones <drjones@redhat.com>,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
        linux-kernel@vger.kernel.org
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Hi Kalesh,


On Mon, Mar 14, 2022 at 8:02 PM Kalesh Singh <kaleshsingh@google.com> wrote:
>
> hyp_alloc_private_va_range() can be used to reserve private VA ranges
> in the nVHE hypervisor. Allocations are aligned based on the order of
> the requested size.
>
> This will be used to implement stack guard pages for KVM nVHE hypervisor
> (nVHE Hyp mode / not pKVM), in a subsequent patch in the series.
>
> Signed-off-by: Kalesh Singh <kaleshsingh@google.com>

This looks good to me. I have also tested this entire series, and your
enhancements will make debugging easier.

Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>

Thanks,
/fuad


> ---
>
> Changes in v6:
>   - Update kernel-doc for hyp_alloc_private_va_range()
>     and add return description, per Stephen
>   - Update hyp_alloc_private_va_range() to return an int error code,
>     per Stephen
>   - Replace IS_ERR() checks with IS_ERR_VALUE() check, per Stephen
>   - Clean up goto, per Stephen
>
> Changes in v5:
>   - Align private allocations based on the order of their size, per Marc
>
> Changes in v4:
>   - Handle null ptr in hyp_alloc_private_va_range() and replace
>     IS_ERR_OR_NULL checks in callers with IS_ERR checks, per Fuad
>   - Fix kernel-doc comments format, per Fuad
>
> Changes in v3:
>   - Handle null ptr in IS_ERR_OR_NULL checks, per Mark
>
>
>  arch/arm64/include/asm/kvm_mmu.h |  1 +
>  arch/arm64/kvm/mmu.c             | 66 +++++++++++++++++++++-----------
>  2 files changed, 45 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 81839e9a8a24..3cc9aa25f510 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -153,6 +153,7 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v)
>  int kvm_share_hyp(void *from, void *to);
>  void kvm_unshare_hyp(void *from, void *to);
>  int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot);
> +int hyp_alloc_private_va_range(size_t size, unsigned long *haddr);
>  int create_hyp_io_mappings(phys_addr_t phys_addr, size_t size,
>                            void __iomem **kaddr,
>                            void __iomem **haddr);
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index bc2aba953299..7326d683c500 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -457,23 +457,22 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
>         return 0;
>  }
>
> -static int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
> -                                       unsigned long *haddr,
> -                                       enum kvm_pgtable_prot prot)
> +
> +/**
> + * hyp_alloc_private_va_range - Allocates a private VA range.
> + * @size:      The size of the VA range to reserve.
> + * @haddr:     The hypervisor virtual start address of the allocation.
> + *
> + * The private virtual address (VA) range is allocated below io_map_base
> + * and aligned based on the order of @size.
> + *
> + * Return: 0 on success or negative error code on failure.
> + */
> +int hyp_alloc_private_va_range(size_t size, unsigned long *haddr)
>  {
>         unsigned long base;
>         int ret = 0;
>
> -       if (!kvm_host_owns_hyp_mappings()) {
> -               base = kvm_call_hyp_nvhe(__pkvm_create_private_mapping,
> -                                        phys_addr, size, prot);
> -               if (IS_ERR_OR_NULL((void *)base))
> -                       return PTR_ERR((void *)base);
> -               *haddr = base;
> -
> -               return 0;
> -       }
> -
>         mutex_lock(&kvm_hyp_pgd_mutex);
>
>         /*
> @@ -484,30 +483,53 @@ static int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
>          *
>          * The allocated size is always a multiple of PAGE_SIZE.
>          */
> -       size = PAGE_ALIGN(size + offset_in_page(phys_addr));
> -       base = io_map_base - size;
> +       base = io_map_base - PAGE_ALIGN(size);
> +
> +       /* Align the allocation based on the order of its size */
> +       base = ALIGN_DOWN(base, PAGE_SIZE << get_order(size));
>
>         /*
>          * Verify that BIT(VA_BITS - 1) hasn't been flipped by
>          * allocating the new area, as it would indicate we've
>          * overflowed the idmap/IO address range.
>          */
> -       if ((base ^ io_map_base) & BIT(VA_BITS - 1))
> +       if (!base || (base ^ io_map_base) & BIT(VA_BITS - 1))
>                 ret = -ENOMEM;
>         else
> -               io_map_base = base;
> +               *haddr = io_map_base = base;
>
>         mutex_unlock(&kvm_hyp_pgd_mutex);
>
> +       return ret;
> +}
> +
> +static int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
> +                                       unsigned long *haddr,
> +                                       enum kvm_pgtable_prot prot)
> +{
> +       unsigned long addr;
> +       int ret = 0;
> +
> +       if (!kvm_host_owns_hyp_mappings()) {
> +               addr = kvm_call_hyp_nvhe(__pkvm_create_private_mapping,
> +                                        phys_addr, size, prot);
> +               if (IS_ERR_VALUE(addr))
> +                       return addr;
> +               *haddr = addr;
> +
> +               return 0;
> +       }
> +
> +       size += offset_in_page(phys_addr);
> +       ret = hyp_alloc_private_va_range(size, &addr);
>         if (ret)
> -               goto out;
> +               return ret;
>
> -       ret = __create_hyp_mappings(base, size, phys_addr, prot);
> +       ret = __create_hyp_mappings(addr, size, phys_addr, prot);
>         if (ret)
> -               goto out;
> +               return ret;
>
> -       *haddr = base + offset_in_page(phys_addr);
> -out:
> +       *haddr = addr + offset_in_page(phys_addr);
>         return ret;
>  }
>
> --
> 2.35.1.723.g4982287a31-goog
>