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From:   Kalesh Singh <kaleshsingh@google.com>
Date:   Tue, 29 Mar 2022 08:37:57 -0700
Message-ID: <CAC_TJvc_N7jcn2eevyQW2gpfk=aZ6KvzQeioKe-G7znaSzQ46w@mail.gmail.com>
Subject: Re: [PATCH v6 1/8] KVM: arm64: Introduce hyp_alloc_private_va_range()
To:     Fuad Tabba <tabba@google.com>
Cc:     Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
        Quentin Perret <qperret@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        "Cc: Android Kernel" <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>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@lists.infradead.org>,
        kvmarm <kvmarm@lists.cs.columbia.edu>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, Mar 29, 2022 at 1:51 AM Fuad Tabba <tabba@google.com> wrote:
>
> 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 for the reviews Fuad :)

- Kalesh


-Kalesh
>
> 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
> >