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Message-ID: <87bkx8cdt4.wl-maz@kernel.org>
Date: Mon, 11 Apr 2022 07:52:07 +0100
From: Marc Zyngier <maz@...nel.org>
To: Kalesh Singh <kaleshsingh@...gle.com>
Cc: will@...nel.org, qperret@...gle.com, tabba@...gle.com,
surenb@...gle.com, kernel-team@...roid.com,
James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Catalin Marinas <catalin.marinas@....com>,
Mark Rutland <mark.rutland@....com>,
Zenghui Yu <yuzenghui@...wei.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Changbin Du <changbin.du@...el.com>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/6] KVM: arm64: Introduce hyp_alloc_private_va_range()
On Fri, 08 Apr 2022 21:03:24 +0100,
Kalesh Singh <kaleshsingh@...gle.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@...gle.com>
> Tested-by: Fuad Tabba <tabba@...gle.com>
> Reviewed-by: Fuad Tabba <tabba@...gle.com>
> ---
>
> Changes in v7:
> - Add Fuad's Reviewed-by and Tested-by tags.
>
> 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 74735a864eee..a50cbb5ba402 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -154,6 +154,7 @@ 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 0d19259454d8..3d3efea4e991 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))
I don't get this '!base' check. Why isn't it encompassed by the
'VA_BITS - 1' flip check?
> 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);
This hardly makes any sense on its own. I get it that it is still
doing the right thing as hyp_alloc_private_va_range() will fix it up,
but I'd rather you keep the PAGE_ALIGN() here, even if it ends up
being duplicated.
> + 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;
> }
>
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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