linux-kernel - Re: [PATCH v3 11/11] KVM: x86: Introduce KVM_SET_PAGE_ENC

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Date:   Thu, 14 Nov 2019 17:22:06 -0800
From:   Steve Rutherford <srutherford@...gle.com>
To:     "Singh, Brijesh" <brijesh.singh@....com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...e.de>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 11/11] KVM: x86: Introduce KVM_SET_PAGE_ENC_BITMAP ioctl

On Wed, Jul 10, 2019 at 1:13 PM Singh, Brijesh <brijesh.singh@....com> wrote:
>
>  struct kvm_arch_async_pf {
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index e675fd89bb9a..31653e8d5927 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -7466,6 +7466,47 @@ static int svm_get_page_enc_bitmap(struct kvm *kvm,
>         return ret;
>  }
>
> +static int svm_set_page_enc_bitmap(struct kvm *kvm,
> +                                  struct kvm_page_enc_bitmap *bmap)
> +{
> +       struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +       unsigned long gfn_start, gfn_end;
> +       unsigned long *bitmap;
> +       unsigned long sz, i;
> +       int ret;
> +
> +       if (!sev_guest(kvm))
> +               return -ENOTTY;
> +
> +       gfn_start = bmap->start_gfn;
> +       gfn_end = gfn_start + bmap->num_pages;
> +
> +       sz = ALIGN(bmap->num_pages, BITS_PER_LONG) / 8;
> +       bitmap = kmalloc(sz, GFP_KERNEL);

This kmalloc should probably be either a vmalloc or kvmalloc. The max
size, if I'm reading kmalloc correctly, is 2^10 pages. That's 4MB,
which should correspond to a bitmap for a 128GB VM, which is a
plausible VM size.

--Steve