On Wed, 11 Aug 2021 05:52:29 +0100,
Anshuman Khandual <anshuman.khandual@xxxxxxx> wrote:
>
> Even though ID_AA64MMFR0.PARANGE reports 52 bit PA size support, it cannot
> be enabled as guest IPA size on 4K or 16K page size configurations. Hence
> kvm_ipa_limit must be restricted to 48 bits. This change achieves required
> IPA capping.
>
> Before the commit c9b69a0cf0b4 ("KVM: arm64: Don't constrain maximum IPA
> size based on host configuration"), the problem here would have been just
> latent via PHYS_MASK_SHIFT (which earlier in turn capped kvm_ipa_limit),
> which remains capped at 48 bits on 4K and 16K configs.
>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: James Morse <james.morse@xxxxxxx>
> Cc: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Fixes: c9b69a0cf0b4 ("KVM: arm64: Don't constrain maximum IPA size based on host configuration")
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> This applies on v5.14-rc5
>
> arch/arm64/kvm/reset.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 20588220fe66..e66974c4b9d3 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -337,6 +337,15 @@ int kvm_set_ipa_limit(void)
> return -EINVAL;
> }
>
> + /*
> + * IPA size beyond 48 bits could not be supported
> + * on either 4K or 16K page size. Hence let's cap
> + * it to 48 bits, in case it's reported as larger
> + * on the system.
> + */
> + if (!IS_ENABLED(CONFIG_ARM64_64K_PAGES))
As per our earlier discussion, please use (PAGE_SIZE != SZ_64K)
instead. This is in keeping with the rest of the file.
> + parange = min(parange, (unsigned int)ID_AA64MMFR0_PARANGE_48);
> +
Also, please move it next to the point where we assign parange.
> kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange);
> kvm_info("IPA Size Limit: %d bits%s\n", kvm_ipa_limit,
> ((kvm_ipa_limit < KVM_PHYS_SHIFT) ?
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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