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From: Ashish Kalra <Ashish.Kalra@amd.com>
To: pbonzini@redhat.com
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	rkrcmar@redhat.com, joro@8bytes.org, bp@suse.de,
	thomas.lendacky@amd.com, x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, srutherford@google.com,
	venu.busireddy@oracle.com, brijesh.singh@amd.com
Subject: [PATCH v9 18/18] KVM: SVM: Bypass DBG_DECRYPT API calls for unecrypted guest memory.
Date: Tue,  8 Dec 2020 22:09:16 +0000	[thread overview]
Message-ID: <aa3b3b645f282d778d2eaf6b118df85d08ae43d7.1607460588.git.ashish.kalra@amd.com> (raw)
In-Reply-To: <cover.1607460588.git.ashish.kalra@amd.com>

From: Ashish Kalra <ashish.kalra@amd.com>

For all explicitly unecrypted guest memory regions such as S/W IOTLB
bounce buffers, dma_decrypted() allocated regions and for guest regions
marked as "__bss_decrypted", ensure that DBG_DECRYPT API calls are
bypassed for such regions. The guest memory regions encryption status
is referenced using the page encryption bitmap.

Uses the two added infrastructure functions hva_to_memslot() and
hva_to_gfn().

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 arch/x86/kvm/svm/sev.c | 76 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 83565e35fa09..da002945a5ae 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -764,6 +764,37 @@ static int __sev_dbg_encrypt_user(struct kvm *kvm, unsigned long paddr,
 	return ret;
 }
 
+static struct kvm_memory_slot *hva_to_memslot(struct kvm *kvm,
+					      unsigned long hva)
+{
+	struct kvm_memslots *slots = kvm_memslots(kvm);
+	struct kvm_memory_slot *memslot;
+
+	kvm_for_each_memslot(memslot, slots) {
+		if (hva >= memslot->userspace_addr &&
+		    hva < memslot->userspace_addr +
+			      (memslot->npages << PAGE_SHIFT))
+			return memslot;
+	}
+
+	return NULL;
+}
+
+static bool hva_to_gfn(struct kvm *kvm, unsigned long hva, gfn_t *gfn)
+{
+	struct kvm_memory_slot *memslot;
+	gpa_t gpa_offset;
+
+	memslot = hva_to_memslot(kvm, hva);
+	if (!memslot)
+		return false;
+
+	gpa_offset = hva - memslot->userspace_addr;
+	*gfn = ((memslot->base_gfn << PAGE_SHIFT) + gpa_offset) >> PAGE_SHIFT;
+
+	return true;
+}
+
 static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
 {
 	unsigned long vaddr, vaddr_end, next_vaddr;
@@ -793,6 +824,50 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
 	for (; vaddr < vaddr_end; vaddr = next_vaddr) {
 		int len, s_off, d_off;
 
+		if (dec) {
+			struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+			struct page *src_tpage = NULL;
+			gfn_t gfn_start;
+			int srcu_idx;
+
+			/* ensure hva_to_gfn translations remain valid */
+			srcu_idx = srcu_read_lock(&kvm->srcu);
+			if (!hva_to_gfn(kvm, vaddr, &gfn_start)) {
+				srcu_read_unlock(&kvm->srcu, srcu_idx);
+				return -EINVAL;
+			}
+			if (sev->page_enc_bmap) {
+				if (!test_bit(gfn_start, sev->page_enc_bmap)) {
+					src_tpage = alloc_page(GFP_KERNEL);
+					if (!src_tpage) {
+						srcu_read_unlock(&kvm->srcu, srcu_idx);
+						return -ENOMEM;
+					}
+					/*
+					 * Since user buffer may not be page aligned, calculate the
+					 * offset within the page.
+					*/
+					s_off = vaddr & ~PAGE_MASK;
+					d_off = dst_vaddr & ~PAGE_MASK;
+					len = min_t(size_t, (PAGE_SIZE - s_off), size);
+
+					if (copy_from_user(page_address(src_tpage),
+							   (void __user *)(uintptr_t)vaddr, len)) {
+						__free_page(src_tpage);
+						srcu_read_unlock(&kvm->srcu, srcu_idx);
+						return -EFAULT;
+					}
+					if (copy_to_user((void __user *)(uintptr_t)dst_vaddr,
+							 page_address(src_tpage), len)) {
+						ret = -EFAULT;
+					}
+					__free_page(src_tpage);
+					srcu_read_unlock(&kvm->srcu, srcu_idx);
+					goto already_decrypted;
+				}
+			}
+		}
+
 		/* lock userspace source and destination page */
 		src_p = sev_pin_memory(kvm, vaddr & PAGE_MASK, PAGE_SIZE, &n, 0);
 		if (IS_ERR(src_p))
@@ -837,6 +912,7 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
 		sev_unpin_memory(kvm, src_p, n);
 		sev_unpin_memory(kvm, dst_p, n);
 
+already_decrypted:
 		if (ret)
 			goto err;
 
-- 
2.17.1


  parent reply	other threads:[~2020-12-08 22:10 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-08 22:02 [PATCH v9 00/18] Add AMD SEV guest live migration support Ashish Kalra
2020-12-08 22:03 ` [PATCH v9 01/18] KVM: SVM: Add KVM_SEV SEND_START command Ashish Kalra
2020-12-08 22:04 ` [PATCH v9 02/18] KVM: SVM: Add KVM_SEND_UPDATE_DATA command Ashish Kalra
2020-12-08 22:04 ` [PATCH v9 03/18] KVM: SVM: Add KVM_SEV_SEND_FINISH command Ashish Kalra
2020-12-08 22:05 ` [PATCH v9 04/18] KVM: SVM: Add support for KVM_SEV_RECEIVE_START command Ashish Kalra
2020-12-08 22:05 ` [PATCH v9 05/18] KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command Ashish Kalra
2020-12-08 22:05 ` [PATCH v9 06/18] KVM: SVM: Add KVM_SEV_RECEIVE_FINISH command Ashish Kalra
2020-12-08 22:05 ` [PATCH v9 07/18] KVM: x86: Add AMD SEV specific Hypercall3 Ashish Kalra
2020-12-08 22:06 ` [PATCH v9 08/18] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall Ashish Kalra
2020-12-08 22:06 ` [PATCH v9 09/18] KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl Ashish Kalra
2020-12-08 22:06 ` [PATCH v9 10/18] mm: x86: Invoke hypercall when page encryption status is changed Ashish Kalra
2020-12-08 22:07 ` [PATCH v9 11/18] KVM: x86: Introduce KVM_SET_PAGE_ENC_BITMAP ioctl Ashish Kalra
2020-12-08 22:07 ` [PATCH v9 12/18] KVM: SVM: Add support for static allocation of unified Page Encryption Bitmap Ashish Kalra
2020-12-08 22:07 ` [PATCH v9 13/18] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR Ashish Kalra
2020-12-08 22:08 ` [PATCH v9 14/18] EFI: Introduce the new AMD Memory Encryption GUID Ashish Kalra
2020-12-08 22:08 ` [PATCH v9 15/18] KVM: x86: Add guest support for detecting and enabling SEV Live Migration feature Ashish Kalra
2020-12-08 22:08 ` [PATCH v9 16/18] KVM: x86: Mark _bss_decrypted section variables as decrypted in page encryption bitmap Ashish Kalra
2020-12-08 22:09 ` [PATCH v9 17/18] KVM: x86: Add kexec support for SEV Live Migration Ashish Kalra
2020-12-08 22:09 ` Ashish Kalra [this message]
2021-01-15  0:31 ` [PATCH v9 00/18] Add AMD SEV guest live migration support Steve Rutherford
2021-01-15  1:16   ` Kalra, Ashish

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