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    SubjectRe: [PATCH v2 14/17] kvm: arm64: Switch to per VM IPA limit
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    On 13/04/18 17:27, Punit Agrawal wrote:
    > Hi Suzuki,
    >
    > I haven't had a chance to look at the code but noticed one issue below.
    >
    > Suzuki K Poulose <suzuki.poulose@arm.com> writes:
    >
    >> Now that we can manage the stage2 page table per VM, switch the
    >> configuration details to per VM instance. We keep track of the
    >> IPA bits, number of page table levels and the VTCR bits (which
    >> depends on the IPA and the number of levels). While at it, remove
    >> unused pgd_lock field from kvm_arch for arm64.
    >>
    >> Cc: Marc Zyngier <marc.zyngier@arm.com>
    >> Cc: Christoffer Dall <cdall@kernel.org>
    >> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    >> ---
    >> arch/arm64/include/asm/kvm_host.h | 14 ++++++++++++--
    >> arch/arm64/include/asm/kvm_mmu.h | 11 +++++++++--
    >> arch/arm64/include/asm/stage2_pgtable.h | 1 -
    >> arch/arm64/kvm/hyp/switch.c | 3 +--
    >> virt/kvm/arm/mmu.c | 4 ++++
    >> 5 files changed, 26 insertions(+), 7 deletions(-)
    >>
    >
    > [...]
    >
    >> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
    >> index bb458bf..e86d7f4 100644
    >> --- a/arch/arm64/include/asm/kvm_mmu.h
    >> +++ b/arch/arm64/include/asm/kvm_mmu.h
    >> @@ -136,9 +136,10 @@ static inline unsigned long __kern_hyp_va(unsigned long v)
    >> */
    >> #define KVM_PHYS_SHIFT (40)
    >>
    >> -#define kvm_phys_shift(kvm) KVM_PHYS_SHIFT
    >> +#define kvm_phys_shift(kvm) (kvm->arch.phys_shift)
    >> #define kvm_phys_size(kvm) (_AC(1, ULL) << kvm_phys_shift(kvm))
    >> #define kvm_phys_mask(kvm) (kvm_phys_size(kvm) - _AC(1, ULL))
    >> +#define kvm_stage2_levels(kvm) (kvm->arch.s2_levels)
    >>
    >> static inline bool kvm_page_empty(void *ptr)
    >> {
    >
    > [...]
    >
    >> diff --git a/arch/arm64/include/asm/stage2_pgtable.h b/arch/arm64/include/asm/stage2_pgtable.h
    >> index 33e8ebb..9b75b83 100644
    >> --- a/arch/arm64/include/asm/stage2_pgtable.h
    >> +++ b/arch/arm64/include/asm/stage2_pgtable.h
    >> @@ -44,7 +44,6 @@
    >> */
    >> #define __s2_pgd_ptrs(pa, lvls) (1 << ((pa) - pt_levels_pgdir_shift((lvls))))
    >>
    >> -#define kvm_stage2_levels(kvm) stage2_pt_levels(kvm_phys_shift(kvm))
    >> #define stage2_pgdir_shift(kvm) \
    >> pt_levels_pgdir_shift(kvm_stage2_levels(kvm))
    >> #define stage2_pgdir_size(kvm) (_AC(1, UL) << stage2_pgdir_shift((kvm)))
    >
    > [...]
    >
    >> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
    >> index 7a264c6..746f38e 100644
    >> --- a/virt/kvm/arm/mmu.c
    >> +++ b/virt/kvm/arm/mmu.c
    >> @@ -753,6 +753,10 @@ int kvm_alloc_stage2_pgd(struct kvm *kvm)
    >> return -EINVAL;
    >> }
    >>
    >> + /* Make sure we have the stage2 configured for this VM */
    >> + if (WARN_ON(!kvm_stage2_levels(kvm)))
    >> + return -EINVAL;
    >> +
    >
    > This hunk breaks the 32-bit build as kvm_stag2_levels() isn't defined on
    > arm.

    Thanks for spotting. I have fixed this locally in my next version to check
    for the kvm_phys_shift(), as I plan to delay the levels selection to the
    actual allocation of the table, giving us a fall back to increase the level
    if we are unable to allocate contiguous pages (e.g, 16 * 64K pages with say 46bit
    IPA).


    Cheers
    Suzuki

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