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Date: Thu, 24 Feb 2022 09:20:33 -0800
From: Kalesh Singh <kaleshsingh@...gle.com>
To: Fuad Tabba <tabba@...gle.com>
Cc: Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
Quentin Perret <qperret@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
"Cc: Android Kernel" <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>,
Mark Brown <broonie@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Peter Collingbourne <pcc@...gle.com>,
"Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>,
Andrew Scull <ascull@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Ard Biesheuvel <ardb@...nel.org>,
"moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)"
<linux-arm-kernel@...ts.infradead.org>,
kvmarm@...ts.cs.columbia.edu, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/8] KVM: arm64: Introduce hyp_alloc_private_va_range()
On Thu, Feb 24, 2022 at 4:25 AM Fuad Tabba <tabba@...gle.com> wrote:
>
> Hi Kalesh,
>
> On Thu, Feb 24, 2022 at 5:16 AM Kalesh Singh <kaleshsingh@...gle.com> wrote:
> >
> > hyp_alloc_private_va_range() can be used to reserve private VA ranges
> > in the nVHE hypervisor. Also update __create_hyp_private_mapping()
> > to allow specifying an alignment for the private VA mapping.
> >
> > These 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>
> > ---
> >
> > Changes in v3:
> > - Handle null ptr in IS_ERR_OR_NULL checks, per Mark
> >
> > arch/arm64/include/asm/kvm_mmu.h | 4 +++
> > arch/arm64/kvm/mmu.c | 62 ++++++++++++++++++++------------
> > 2 files changed, 43 insertions(+), 23 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> > index 81839e9a8a24..0b0c71302b92 100644
> > --- a/arch/arm64/include/asm/kvm_mmu.h
> > +++ b/arch/arm64/include/asm/kvm_mmu.h
> > @@ -153,6 +153,10 @@ 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);
> > +unsigned long hyp_alloc_private_va_range(size_t size, size_t align);
> > +int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
> > + size_t align, unsigned long *haddr,
> > + enum kvm_pgtable_prot prot);
> > 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..fc09536c8197 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -457,22 +457,16 @@ 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)
> > +
> > +/*
> > + * Allocates a private VA range below io_map_base.
> > + *
> > + * @size: The size of the VA range to reserve.
> > + * @align: The required alignment for the allocation.
> > + */
>
> Many of the functions in this file use the kernel-doc format, and your
> added comments are close, but not quite conforment. If you want to use
> the kernel-doc for these you can refer to:
> https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html
Hi Fuad,
Thanks for the pointer. I will update the function comments to match
when I send the next version.
>
> > +unsigned long hyp_alloc_private_va_range(size_t size, size_t align)
> > {
> > 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);
> >
> > @@ -484,8 +478,8 @@ 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);
> > + base = ALIGN_DOWN(base, align);
> >
> > /*
> > * Verify that BIT(VA_BITS - 1) hasn't been flipped by
> > @@ -493,20 +487,42 @@ static int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
> > * overflowed the idmap/IO address range.
> > */
> > if ((base ^ io_map_base) & BIT(VA_BITS - 1))
> > - ret = -ENOMEM;
> > + base = (unsigned long)ERR_PTR(-ENOMEM);
> > else
> > io_map_base = base;
> >
> > mutex_unlock(&kvm_hyp_pgd_mutex);
> >
> > - if (ret)
> > - goto out;
> > + return base;
> > +}
> > +
> > +int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
> > + size_t align, 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_OR_NULL((void *)addr))
> > + return addr ? PTR_ERR((void *)addr) : -ENOMEM;
> > + *haddr = addr;
> > +
> > + return 0;
> > + }
> > +
> > + size += offset_in_page(phys_addr);
>
> You're not page-aligning the size, which was the behavior before this
> patch. However, looking at where it's being used it seems to be fine
> because the users of size would align it if necessary.
This is now done by hyp_alloc_private_va_range() when calculating the new base:
...
* The allocated size is always a multiple of PAGE_SIZE.
*/
base = io_map_base - PAGE_ALIGN(size);
...
Thanks,
Kalesh
>
> Thanks,
> /fuad
>
>
>
> > + addr = hyp_alloc_private_va_range(size, align);
> > + if (IS_ERR_OR_NULL((void *)addr))
> > + return addr ? PTR_ERR((void *)addr) : -ENOMEM;
> >
> > - ret = __create_hyp_mappings(base, size, phys_addr, prot);
> > + ret = __create_hyp_mappings(addr, size, phys_addr, prot);
> > if (ret)
> > goto out;
> >
> > - *haddr = base + offset_in_page(phys_addr);
> > + *haddr = addr + offset_in_page(phys_addr);
> > out:
> > return ret;
> > }
> > @@ -537,7 +553,7 @@ int create_hyp_io_mappings(phys_addr_t phys_addr, size_t size,
> > return 0;
> > }
> >
> > - ret = __create_hyp_private_mapping(phys_addr, size,
> > + ret = __create_hyp_private_mapping(phys_addr, size, PAGE_SIZE,
> > &addr, PAGE_HYP_DEVICE);
> > if (ret) {
> > iounmap(*kaddr);
> > @@ -564,7 +580,7 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
> >
> > BUG_ON(is_kernel_in_hyp_mode());
> >
> > - ret = __create_hyp_private_mapping(phys_addr, size,
> > + ret = __create_hyp_private_mapping(phys_addr, size, PAGE_SIZE,
> > &addr, PAGE_HYP_EXEC);
> > if (ret) {
> > *haddr = NULL;
> > --
> > 2.35.1.473.g83b2b277ed-goog
> >
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