linux-kernel - Re: [PATCH Part2 v6 26/49] KVM: SVM: Add KVM_SEV_SNP_LAUNCH

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Date:   Tue, 9 Aug 2022 13:55:35 +0000
From:   Sabin Rapan <sabrapan@...zon.com>
To:     <ashish.kalra@....com>
CC:     <ak@...ux.intel.com>, <alpergun@...gle.com>, <ardb@...nel.org>,
        <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
        <dgilbert@...hat.com>, <dovmurik@...ux.ibm.com>, <hpa@...or.com>,
        <jarkko@...nel.org>, <jmattson@...gle.com>, <jroedel@...e.de>,
        <kirill@...temov.name>, <kvm@...r.kernel.org>,
        <linux-coco@...ts.linux.dev>, <linux-crypto@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <luto@...nel.org>, <marcorr@...gle.com>, <michael.roth@....com>,
        <mingo@...hat.com>, <pbonzini@...hat.com>, <peterz@...radead.org>,
        <pgonda@...gle.com>, <rientjes@...gle.com>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>, <seanjc@...gle.com>,
        <slp@...hat.com>, <srinivas.pandruvada@...ux.intel.com>,
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        <tony.luck@...el.com>, <vbabka@...e.cz>, <vkuznets@...hat.com>,
        <x86@...nel.org>
Subject: Re: [PATCH Part2 v6 26/49] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_UPDATE command 

> +static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len)
> +{
> +	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +	struct list_head *head = &sev->regions_list;
> +	struct enc_region *i;
> +
> +	lockdep_assert_held(&kvm->lock);
> +
> +	list_for_each_entry(i, head, list) {
> +		u64 start = i->uaddr;
> +		u64 end = start + i->size;
> +
> +		if (start <= hva && end >= (hva + len))
> +			return true;
> +	}
> +
> +	return false;
> +}

Since KVM_MEMORY_ENCRYPT_REG_REGION should be called for every memory region the user gives to kvm,
is the regions_list any different from kvm's memslots?

> +
> +static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{
> +	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +	struct sev_data_snp_launch_update data = {0};
> +	struct kvm_sev_snp_launch_update params;
> +	unsigned long npages, pfn, n = 0;
> +	int *error = &argp->error;
> +	struct page **inpages;
> +	int ret, i, level;
> +	u64 gfn;
> +
> +	if (!sev_snp_guest(kvm))
> +		return -ENOTTY;
> +
> +	if (!sev->snp_context)
> +		return -EINVAL;
> +
> +	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
> +		return -EFAULT;
> +
> +	/* Verify that the specified address range is registered. */
> +	if (!is_hva_registered(kvm, params.uaddr, params.len))
> +		return -EINVAL;
> +
> +	/*
> +	 * The userspace memory is already locked so technically we don't
> +	 * need to lock it again. Later part of the function needs to know
> +	 * pfn so call the sev_pin_memory() so that we can get the list of
> +	 * pages to iterate through.
> +	 */
> +	inpages = sev_pin_memory(kvm, params.uaddr, params.len, &npages, 1);
> +	if (!inpages)
> +		return -ENOMEM;

sev_pin_memory will call pin_user_pages() which fails for PFNMAP vmas that you
would get if you use memory allocated from an IO driver.
Using gfn_to_pfn instead will make this work with vmas backed by pages or raw
pfn mappings.




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