linux-kernel - Re: [PATCH v2] KVM: SVM: Mark SEV launch secret pages as dirty.

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Date:   Mon, 10 Aug 2020 06:05:52 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Cfir Cohen <cfir@...gle.com>,
        "kvm @ vger . kernel . org" <kvm@...r.kernel.org>,
        Lendacky Thomas <thomas.lendacky@....com>
Cc:     brijesh.singh@....com, Grimm Jon <Jon.Grimm@....com>,
        David Rientjes <rientjes@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: SVM: Mark SEV launch secret pages as dirty.


On 8/7/20 7:37 PM, Cfir Cohen wrote:
> The LAUNCH_SECRET command performs encryption of the
> launch secret memory contents. Mark pinned pages as
> dirty, before unpinning them.
> This matches the logic in sev_launch_update_data().
>
> Signed-off-by: Cfir Cohen <cfir@...gle.com>
> ---
> Changelog since v1:
>  - Updated commit message.
>
>  arch/x86/kvm/svm/sev.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)


Reviewed-by: Brijesh Singh <brijesh.singh@....com>


>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 5573a97f1520..37c47d26b9f7 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -850,7 +850,7 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  	struct kvm_sev_launch_secret params;
>  	struct page **pages;
>  	void *blob, *hdr;
> -	unsigned long n;
> +	unsigned long n, i;
>  	int ret, offset;
>  
>  	if (!sev_guest(kvm))
> @@ -863,6 +863,14 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  	if (!pages)
>  		return -ENOMEM;
>  
> +	/*
> +	 * The LAUNCH_SECRET command will perform in-place encryption of the
> +	 * memory content (i.e it will write the same memory region with C=1).
> +	 * It's possible that the cache may contain the data with C=0, i.e.,
> +	 * unencrypted so invalidate it first.
> +	 */
> +	sev_clflush_pages(pages, n);
> +
>  	/*
>  	 * The secret must be copied into contiguous memory region, lets verify
>  	 * that userspace memory pages are contiguous before we issue command.
> @@ -908,6 +916,11 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  e_free:
>  	kfree(data);
>  e_unpin_memory:
> +	/* content of memory is updated, mark pages dirty */
> +	for (i = 0; i < n; i++) {
> +		set_page_dirty_lock(pages[i]);
> +		mark_page_accessed(pages[i]);
> +	}
>  	sev_unpin_memory(kvm, pages, n);
>  	return ret;
>  }