Patch "ptp: kvm: Use decrypted memory in confidential guest on x86" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    ptp: kvm: Use decrypted memory in confidential guest on x86

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ptp-kvm-use-decrypted-memory-in-confidential-guest-o.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 964938b57973aa98873a83f16c3bf921e8c01cdd
Author: Jeremi Piotrowski <jpiotrowski@xxxxxxxxxxxxxxxxxxx>
Date:   Wed Mar 8 15:05:31 2023 +0000

    ptp: kvm: Use decrypted memory in confidential guest on x86
    
    [ Upstream commit 6365ba64b4dbe8b59ddaeaa724b281f3787715d5 ]
    
    KVM_HC_CLOCK_PAIRING currently fails inside SEV-SNP guests because the
    guest passes an address to static data to the host. In confidential
    computing the host can't access arbitrary guest memory so handling the
    hypercall runs into an "rmpfault". To make the hypercall work, the guest
    needs to explicitly mark the memory as decrypted. Do that in
    kvm_arch_ptp_init(), but retain the previous behavior for
    non-confidential guests to save us from having to allocate memory.
    
    Add a new arch-specific function (kvm_arch_ptp_exit()) to free the
    allocation and mark the memory as encrypted again.
    
    Signed-off-by: Jeremi Piotrowski <jpiotrowski@xxxxxxxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230308150531.477741-1-jpiotrowski@xxxxxxxxxxxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Stable-dep-of: 5e7aa97c7acf ("ptp: kvm: x86: Return EOPNOTSUPP instead of ENODEV from kvm_arch_ptp_init()")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/ptp/ptp_kvm_arm.c b/drivers/ptp/ptp_kvm_arm.c
index b7d28c8dfb84..e68e6943167b 100644
--- a/drivers/ptp/ptp_kvm_arm.c
+++ b/drivers/ptp/ptp_kvm_arm.c
@@ -22,6 +22,10 @@ int kvm_arch_ptp_init(void)
 	return 0;
 }
 
+void kvm_arch_ptp_exit(void)
+{
+}
+
 int kvm_arch_ptp_get_clock(struct timespec64 *ts)
 {
 	return kvm_arch_ptp_get_crosststamp(NULL, ts, NULL);
diff --git a/drivers/ptp/ptp_kvm_common.c b/drivers/ptp/ptp_kvm_common.c
index fcae32f56f25..051114a59286 100644
--- a/drivers/ptp/ptp_kvm_common.c
+++ b/drivers/ptp/ptp_kvm_common.c
@@ -130,6 +130,7 @@ static struct kvm_ptp_clock kvm_ptp_clock;
 static void __exit ptp_kvm_exit(void)
 {
 	ptp_clock_unregister(kvm_ptp_clock.ptp_clock);
+	kvm_arch_ptp_exit();
 }
 
 static int __init ptp_kvm_init(void)
diff --git a/drivers/ptp/ptp_kvm_x86.c b/drivers/ptp/ptp_kvm_x86.c
index 4991054a2135..902844cc1a17 100644
--- a/drivers/ptp/ptp_kvm_x86.c
+++ b/drivers/ptp/ptp_kvm_x86.c
@@ -14,27 +14,64 @@
 #include <uapi/linux/kvm_para.h>
 #include <linux/ptp_clock_kernel.h>
 #include <linux/ptp_kvm.h>
+#include <linux/set_memory.h>
 
 static phys_addr_t clock_pair_gpa;
-static struct kvm_clock_pairing clock_pair;
+static struct kvm_clock_pairing clock_pair_glbl;
+static struct kvm_clock_pairing *clock_pair;
 
 int kvm_arch_ptp_init(void)
 {
+	struct page *p;
 	long ret;
 
 	if (!kvm_para_available())
 		return -ENODEV;
 
-	clock_pair_gpa = slow_virt_to_phys(&clock_pair);
-	if (!pvclock_get_pvti_cpu0_va())
-		return -ENODEV;
+	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
+		p = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		if (!p)
+			return -ENOMEM;
+
+		clock_pair = page_address(p);
+		ret = set_memory_decrypted((unsigned long)clock_pair, 1);
+		if (ret) {
+			__free_page(p);
+			clock_pair = NULL;
+			goto nofree;
+		}
+	} else {
+		clock_pair = &clock_pair_glbl;
+	}
+
+	clock_pair_gpa = slow_virt_to_phys(clock_pair);
+	if (!pvclock_get_pvti_cpu0_va()) {
+		ret = -ENODEV;
+		goto err;
+	}
 
 	ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
 			     KVM_CLOCK_PAIRING_WALLCLOCK);
-	if (ret == -KVM_ENOSYS)
-		return -ENODEV;
+	if (ret == -KVM_ENOSYS) {
+		ret = -ENODEV;
+		goto err;
+	}
 
 	return ret;
+
+err:
+	kvm_arch_ptp_exit();
+nofree:
+	return ret;
+}
+
+void kvm_arch_ptp_exit(void)
+{
+	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
+		WARN_ON(set_memory_encrypted((unsigned long)clock_pair, 1));
+		free_page((unsigned long)clock_pair);
+		clock_pair = NULL;
+	}
 }
 
 int kvm_arch_ptp_get_clock(struct timespec64 *ts)
@@ -49,8 +86,8 @@ int kvm_arch_ptp_get_clock(struct timespec64 *ts)
 		return -EOPNOTSUPP;
 	}
 
-	ts->tv_sec = clock_pair.sec;
-	ts->tv_nsec = clock_pair.nsec;
+	ts->tv_sec = clock_pair->sec;
+	ts->tv_nsec = clock_pair->nsec;
 
 	return 0;
 }
@@ -81,9 +118,9 @@ int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
 			pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
 			return -EOPNOTSUPP;
 		}
-		tspec->tv_sec = clock_pair.sec;
-		tspec->tv_nsec = clock_pair.nsec;
-		*cycle = __pvclock_read_cycles(src, clock_pair.tsc);
+		tspec->tv_sec = clock_pair->sec;
+		tspec->tv_nsec = clock_pair->nsec;
+		*cycle = __pvclock_read_cycles(src, clock_pair->tsc);
 	} while (pvclock_read_retry(src, version));
 
 	*cs = &kvm_clock;
diff --git a/include/linux/ptp_kvm.h b/include/linux/ptp_kvm.h
index c2e28deef33a..746fd67c3480 100644
--- a/include/linux/ptp_kvm.h
+++ b/include/linux/ptp_kvm.h
@@ -14,6 +14,7 @@ struct timespec64;
 struct clocksource;
 
 int kvm_arch_ptp_init(void);
+void kvm_arch_ptp_exit(void);
 int kvm_arch_ptp_get_clock(struct timespec64 *ts);
 int kvm_arch_ptp_get_crosststamp(u64 *cycle,
 		struct timespec64 *tspec, struct clocksource **cs);




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