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Date: Thu, 2 Apr 2020 18:31:54 -0700
From: Krish Sadhukhan <krish.sadhukhan@...cle.com>
To: Ashish Kalra <Ashish.Kalra@....com>, pbonzini@...hat.com
Cc: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
joro@...tes.org, bp@...e.de, thomas.lendacky@....com,
x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
rientjes@...gle.com, srutherford@...gle.com, luto@...nel.org,
brijesh.singh@....com
Subject: Re: [PATCH v6 08/14] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS
hypercall
On 3/29/20 11:22 PM, Ashish Kalra wrote:
> From: Brijesh Singh <Brijesh.Singh@....com>
>
> This hypercall is used by the SEV guest to notify a change in the page
> encryption status to the hypervisor. The hypercall should be invoked
> only when the encryption attribute is changed from encrypted -> decrypted
> and vice versa. By default all guest pages are considered encrypted.
>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: "Radim Krčmář" <rkrcmar@...hat.com>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: x86@...nel.org
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
> Documentation/virt/kvm/hypercalls.rst | 15 +++++
> arch/x86/include/asm/kvm_host.h | 2 +
> arch/x86/kvm/svm.c | 95 +++++++++++++++++++++++++++
> arch/x86/kvm/vmx/vmx.c | 1 +
> arch/x86/kvm/x86.c | 6 ++
> include/uapi/linux/kvm_para.h | 1 +
> 6 files changed, 120 insertions(+)
>
> diff --git a/Documentation/virt/kvm/hypercalls.rst b/Documentation/virt/kvm/hypercalls.rst
> index dbaf207e560d..ff5287e68e81 100644
> --- a/Documentation/virt/kvm/hypercalls.rst
> +++ b/Documentation/virt/kvm/hypercalls.rst
> @@ -169,3 +169,18 @@ a0: destination APIC ID
>
> :Usage example: When sending a call-function IPI-many to vCPUs, yield if
> any of the IPI target vCPUs was preempted.
> +
> +
> +8. KVM_HC_PAGE_ENC_STATUS
> +-------------------------
> +:Architecture: x86
> +:Status: active
> +:Purpose: Notify the encryption status changes in guest page table (SEV guest)
> +
> +a0: the guest physical address of the start page
> +a1: the number of pages
> +a2: encryption attribute
> +
> + Where:
> + * 1: Encryption attribute is set
> + * 0: Encryption attribute is cleared
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 98959e8cd448..90718fa3db47 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1267,6 +1267,8 @@ struct kvm_x86_ops {
>
> bool (*apic_init_signal_blocked)(struct kvm_vcpu *vcpu);
> int (*enable_direct_tlbflush)(struct kvm_vcpu *vcpu);
> + int (*page_enc_status_hc)(struct kvm *kvm, unsigned long gpa,
> + unsigned long sz, unsigned long mode);
> };
>
> struct kvm_arch_async_pf {
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 7c2721e18b06..1d8beaf1bceb 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -136,6 +136,8 @@ struct kvm_sev_info {
> int fd; /* SEV device fd */
> unsigned long pages_locked; /* Number of pages locked */
> struct list_head regions_list; /* List of registered regions */
> + unsigned long *page_enc_bmap;
> + unsigned long page_enc_bmap_size;
> };
>
> struct kvm_svm {
> @@ -1991,6 +1993,9 @@ static void sev_vm_destroy(struct kvm *kvm)
>
> sev_unbind_asid(kvm, sev->handle);
> sev_asid_free(sev->asid);
> +
> + kvfree(sev->page_enc_bmap);
> + sev->page_enc_bmap = NULL;
> }
>
> static void avic_vm_destroy(struct kvm *kvm)
> @@ -7593,6 +7598,94 @@ static int sev_receive_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
> return ret;
> }
>
> +static int sev_resize_page_enc_bitmap(struct kvm *kvm, unsigned long new_size)
> +{
> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> + unsigned long *map;
> + unsigned long sz;
> +
> + if (sev->page_enc_bmap_size >= new_size)
> + return 0;
> +
> + sz = ALIGN(new_size, BITS_PER_LONG) / 8;
> +
> + map = vmalloc(sz);
Just wondering why we can't directly modify sev->page_enc_bmap.
> + if (!map) {
> + pr_err_once("Failed to allocate encrypted bitmap size %lx\n",
> + sz);
> + return -ENOMEM;
> + }
> +
> + /* mark the page encrypted (by default) */
> + memset(map, 0xff, sz);
> +
> + bitmap_copy(map, sev->page_enc_bmap, sev->page_enc_bmap_size);
> + kvfree(sev->page_enc_bmap);
> +
> + sev->page_enc_bmap = map;
> + sev->page_enc_bmap_size = new_size;
> +
> + return 0;
> +}
> +
> +static int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
> + unsigned long npages, unsigned long enc)
> +{
> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> + kvm_pfn_t pfn_start, pfn_end;
> + gfn_t gfn_start, gfn_end;
> + int ret;
> +
> + if (!sev_guest(kvm))
> + return -EINVAL;
> +
> + if (!npages)
> + return 0;
> +
> + gfn_start = gpa_to_gfn(gpa);
> + gfn_end = gfn_start + npages;
> +
> + /* out of bound access error check */
> + if (gfn_end <= gfn_start)
> + return -EINVAL;
> +
> + /* lets make sure that gpa exist in our memslot */
> + pfn_start = gfn_to_pfn(kvm, gfn_start);
> + pfn_end = gfn_to_pfn(kvm, gfn_end);
> +
> + if (is_error_noslot_pfn(pfn_start) && !is_noslot_pfn(pfn_start)) {
> + /*
> + * Allow guest MMIO range(s) to be added
> + * to the page encryption bitmap.
> + */
> + return -EINVAL;
> + }
> +
> + if (is_error_noslot_pfn(pfn_end) && !is_noslot_pfn(pfn_end)) {
> + /*
> + * Allow guest MMIO range(s) to be added
> + * to the page encryption bitmap.
> + */
> + return -EINVAL;
> + }
It seems is_error_noslot_pfn() covers both cases - i) gfn slot is
absent, ii) failure to translate to pfn. So do we still need
is_noslot_pfn() ?
> +
> + mutex_lock(&kvm->lock);
> + ret = sev_resize_page_enc_bitmap(kvm, gfn_end);
> + if (ret)
> + goto unlock;
> +
> + if (enc)
> + __bitmap_set(sev->page_enc_bmap, gfn_start,
> + gfn_end - gfn_start);
> + else
> + __bitmap_clear(sev->page_enc_bmap, gfn_start,
> + gfn_end - gfn_start);
> +
> +unlock:
> + mutex_unlock(&kvm->lock);
> + return ret;
> +}
> +
> static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> {
> struct kvm_sev_cmd sev_cmd;
> @@ -7995,6 +8088,8 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
> .need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
>
> .apic_init_signal_blocked = svm_apic_init_signal_blocked,
> +
> + .page_enc_status_hc = svm_page_enc_status_hc,
Why not place it where other encryption ops are located ?
...
.mem_enc_unreg_region
+ .page_enc_status_hc = svm_page_enc_status_hc
> };
>
> static int __init svm_init(void)
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 079d9fbf278e..f68e76ee7f9c 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -8001,6 +8001,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> .nested_get_evmcs_version = NULL,
> .need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
> .apic_init_signal_blocked = vmx_apic_init_signal_blocked,
> + .page_enc_status_hc = NULL,
> };
>
> static void vmx_cleanup_l1d_flush(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index cf95c36cb4f4..68428eef2dde 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7564,6 +7564,12 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> kvm_sched_yield(vcpu->kvm, a0);
> ret = 0;
> break;
> + case KVM_HC_PAGE_ENC_STATUS:
> + ret = -KVM_ENOSYS;
> + if (kvm_x86_ops->page_enc_status_hc)
> + ret = kvm_x86_ops->page_enc_status_hc(vcpu->kvm,
> + a0, a1, a2);
> + break;
> default:
> ret = -KVM_ENOSYS;
> break;
> diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
> index 8b86609849b9..847b83b75dc8 100644
> --- a/include/uapi/linux/kvm_para.h
> +++ b/include/uapi/linux/kvm_para.h
> @@ -29,6 +29,7 @@
> #define KVM_HC_CLOCK_PAIRING 9
> #define KVM_HC_SEND_IPI 10
> #define KVM_HC_SCHED_YIELD 11
> +#define KVM_HC_PAGE_ENC_STATUS 12
>
> /*
> * hypercalls use architecture specific
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