Re: [RFC PATCH v1 08/10] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall

Lendacky, Thomas
2019-04-26T21:39:50Z

On 4/24/19 11:10 AM, Singh, Brijesh wrote:
> The hypercall can be used by the SEV guest to notify the page encryption

This hyercall is used by the SEV guest to notify a change in the page...

> 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 the guest pages should be considered encrypted.

By default all guest page are considered

>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: x86@kernel.org
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> Documentation/virtual/kvm/hypercalls.txt | 14 +++++
> arch/x86/include/asm/kvm_host.h | 2 +
> arch/x86/kvm/svm.c | 69 ++++++++++++++++++++++++
> arch/x86/kvm/vmx/vmx.c | 1 +
> arch/x86/kvm/x86.c | 5 ++
> include/uapi/linux/kvm_para.h | 1 +
> 6 files changed, 92 insertions(+)
>
> diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
> index da24c138c8d1..ecd44e488679 100644
> --- a/Documentation/virtual/kvm/hypercalls.txt
> +++ b/Documentation/virtual/kvm/hypercalls.txt
> @@ -141,3 +141,17 @@ a0 corresponds to the APIC ID in the third argument (a2), bit 1
> corresponds to the APIC ID a2+1, and so on.
>
> Returns the number of CPUs to which the IPIs were delivered successfully.
> +
> +7. 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: set or clear the encryption attribute

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 a9d03af34030..adb0ca035b97 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1196,6 +1196,8 @@ struct kvm_x86_ops {
> uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);
>
> bool (*need_emulation_on_page_fault)(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 74b57ab742ad..f024f208b052 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -138,6 +138,8 @@ 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 {
> @@ -1911,6 +1913,8 @@ static void sev_vm_destroy(struct kvm *kvm)
>
> sev_unbind_asid(kvm, sev->handle);
> sev_asid_free(kvm);
> +
> + kvfree(sev->page_enc_bmap);
> }
>
> static void avic_vm_destroy(struct kvm *kvm)
> @@ -7370,6 +7374,69 @@ 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;
> +
> + if (sz > PAGE_SIZE)
> + map = vmalloc(sz);
> + else
> + map = kmalloc(sz, GFP_KERNEL);

Any reason this can't always be vmalloc()?

> +
> + if (!map) {
> + pr_err_once("Failed to allocate decrypted bitmap size %lx\n", sz);
> + return 1;

Should this be -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;
> + gfn_t gfn_start, gfn_end;
> + int r;

int ret; ? "r" at first confused me.

> +
> + if (!npages)
> + return 0;
> +
> + gfn_start = gpa_to_gfn(gpa);
> + gfn_end = gfn_start + npages;
> +
> + mutex_lock(&kvm->lock);
> +
> + r = 1;
> + if (sev_resize_page_enc_bitmap(kvm, gfn_end))

ret = sev_resize_...
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);
> +
> + r = 0;

If you do the above, this is not needed.

Thanks,
Tom

> +unlock:
> + mutex_unlock(&kvm->lock);
> + return r;
> +}
> +
> static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> {
> struct kvm_sev_cmd sev_cmd;
> @@ -7711,6 +7778,8 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
> .nested_get_evmcs_version = nested_get_evmcs_version,
>
> .need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
> +
> + .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 b4e7d645275a..9c814e560e0f 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7731,6 +7731,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> .get_vmcs12_pages = NULL,
> .nested_enable_evmcs = NULL,
> .need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
> + .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 a0d1fc80ac5a..dea644be5992 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7141,6 +7141,11 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> case KVM_HC_SEND_IPI:
> ret = kvm_pv_send_ipi(vcpu->kvm, a0, a1, a2, a3, op_64_bit);
> 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 6c0ce49931e5..3dc9e579f4f9 100644
> --- a/include/uapi/linux/kvm_para.h
> +++ b/include/uapi/linux/kvm_para.h
> @@ -28,6 +28,7 @@
> #define KVM_HC_MIPS_CONSOLE_OUTPUT 8
> #define KVM_HC_CLOCK_PAIRING 9
> #define KVM_HC_SEND_IPI 10
> +#define KVM_HC_PAGE_ENC_STATUS 11
>
> /*
> * hypercalls use architecture specific
>