linux-kernel - Re: [PATCH V5 5/7] KVM: selftests: add library for creating/interacting with SEV guests

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Date:   Thu, 22 Dec 2022 14:19:31 -0800
From:   Vishal Annapurve <vannapurve@...gle.com>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        marcorr@...gle.com, seanjc@...gle.com, michael.roth@....com,
        thomas.lendacky@....com, joro@...tes.org, mizhang@...gle.com,
        pbonzini@...hat.com, andrew.jones@...ux.dev
Subject: Re: [PATCH V5 5/7] KVM: selftests: add library for
 creating/interacting with SEV guests

On Tue, Oct 18, 2022 at 1:59 PM Peter Gonda <pgonda@...gle.com> wrote:
>
> ...
> +
> +static void configure_sev_pte_masks(struct kvm_vm *vm)
> +{
> +       uint32_t eax, ebx, ecx, edx, enc_bit;
> +
> +       cpuid(CPUID_MEM_ENC_LEAF, &eax, &ebx, &ecx, &edx);
> +       enc_bit = ebx & CPUID_EBX_CBIT_MASK;
> +
> +       vm->arch.c_bit = 1 << enc_bit;

This should be 1ULL << enc_bit as the overall result overflows 32 bits.

> +       vm->arch.pte_me_mask = vm->arch.c_bit | vm->arch.s_bit;

Maybe the role of pte_me_mask needs to be discussed in more detail. If
pte_me_mask is to be used only for maintaining/manipulating encryption
of page table memory then maybe it should be just set as
vm->arch.c_bit or better yet replaced with vm->arch.c_bit.

gpa_protected_mask also needs to be set here so that vm_untag_gpa
works as expected.

> +       vm->protected = true;
> +}
> +
> ...
> +}

> --
> 2.38.0.413.g74048e4d9e-goog
>