linux-kernel - Re: [PATCH v5 6/6] x86/kvm: Add kexec support for SEV Live Migration.

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Date:   Tue, 17 Aug 2021 15:50:22 -0700
From:   Steve Rutherford <srutherford@...gle.com>
To:     Ashish Kalra <Ashish.Kalra@....com>
Cc:     pbonzini@...hat.com, seanjc@...gle.com, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, joro@...tes.org, bp@...en8.de,
        thomas.lendacky@....com, x86@...nel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, brijesh.singh@....com
Subject: Re: [PATCH v5 6/6] x86/kvm: Add kexec support for SEV Live Migration.

On Tue, Jun 29, 2021 at 8:14 AM Ashish Kalra <Ashish.Kalra@....com> wrote:
>
> From: Ashish Kalra <ashish.kalra@....com>
>
> Reset the host's shared pages list related to kernel
> specific page encryption status settings before we load a
> new kernel by kexec. We cannot reset the complete
> shared pages list here as we need to retain the
> UEFI/OVMF firmware specific settings.
>
> The host's shared pages list is maintained for the
> guest to keep track of all unencrypted guest memory regions,
> therefore we need to explicitly mark all shared pages as
> encrypted again before rebooting into the new guest kernel.
>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
>  arch/x86/kernel/kvm.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index a014c9bb5066..a55712ee58a1 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -869,10 +869,35 @@ static void __init kvm_init_platform(void)
>         if (sev_active() &&
>             kvm_para_has_feature(KVM_FEATURE_MIGRATION_CONTROL)) {
>                 unsigned long nr_pages;
> +               int i;
>
>                 pv_ops.mmu.notify_page_enc_status_changed =
>                         kvm_sev_hc_page_enc_status;
>
> +               /*
> +                * Reset the host's shared pages list related to kernel
> +                * specific page encryption status settings before we load a
> +                * new kernel by kexec. Reset the page encryption status
> +                * during early boot intead of just before kexec to avoid SMP
> +                * races during kvm_pv_guest_cpu_reboot().
> +                * NOTE: We cannot reset the complete shared pages list
> +                * here as we need to retain the UEFI/OVMF firmware
> +                * specific settings.
> +                */
> +
> +               for (i = 0; i < e820_table->nr_entries; i++) {
> +                       struct e820_entry *entry = &e820_table->entries[i];
> +
> +                       if (entry->type != E820_TYPE_RAM)
> +                               continue;
> +
> +                       nr_pages = DIV_ROUND_UP(entry->size, PAGE_SIZE);
> +
> +                       kvm_hypercall3(KVM_HC_MAP_GPA_RANGE, entry->addr,
> +                                      nr_pages,
> +                                      KVM_MAP_GPA_RANGE_ENCRYPTED | KVM_MAP_GPA_RANGE_PAGE_SZ_4K);
> +               }
> +
>                 /*
>                  * Ensure that _bss_decrypted section is marked as decrypted in the
>                  * shared pages list.
> --
> 2.17.1
>
I believe this entire series has been reviewed. Is there any appetite
to queue these for 915?
They may need to be resent, since I'm not sure there is a single patch
series that contains all the patches.

--Steve