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Message-ID: <2d710143-0e28-5534-7858-81eb296d3445@oracle.com>
Date: Mon, 6 Apr 2020 15:27:08 -0700
From: Krish Sadhukhan <krish.sadhukhan@...cle.com>
To: Ashish Kalra <ashish.kalra@....com>
Cc: pbonzini@...hat.com, 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 4/2/20 7:58 PM, Ashish Kalra wrote:
> On Fri, Apr 03, 2020 at 01:57:48AM +0000, Ashish Kalra wrote:
>> On Thu, Apr 02, 2020 at 06:31:54PM -0700, Krish Sadhukhan wrote:
>>> 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.
>>>
>> Because the page_enc_bitmap needs to be re-sized here, it needs to be
>> expanded here.
OK.
> I don't believe there is anything is like a realloc() kind of equivalent
> for the kmalloc() interfaces.
>
> Thanks,
> Ashish
>
>>>> + 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() ?
>>>
>> We do need to check for !is_noslot_pfn(..) additionally as the MMIO ranges will not
>> be having a slot allocated.
The comments above is_error_noslot_pfn() seem to indicate that it covers
both cases, "not in slot" and "failure to translate"...
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@...cle.com>
>>
>> Thanks,
>> Ashish
>>
>>>> +
>>>> + 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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