[PATCH v2 4/4] x86/vmware: Support steal time clock for encrypted guests

[Alexey Makhalov <alexey.makhalov@broadcom.com>]

Shared memory containing steal time counter should be set to
decrypted when guest memory is encrypted.

Co-developed-by: Bo Gan <bo.gan@broadcom.com>
Signed-off-by: Bo Gan <bo.gan@broadcom.com>
Signed-off-by: Alexey Makhalov <alexey.makhalov@broadcom.com>
---
 arch/x86/kernel/cpu/vmware.c | 41 ++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index c631e577348a..523a9b99847d 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -32,6 +32,7 @@
 #include <linux/sched/cputime.h>
 #include <linux/kmsg_dump.h>
 #include <linux/panic_notifier.h>
+#include <linux/set_memory.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
@@ -39,6 +40,7 @@
 #include <asm/apic.h>
 #include <asm/vmware.h>
 #include <asm/svm.h>
+#include <asm/coco.h>
 
 #undef pr_fmt
 #define pr_fmt(fmt)	"vmware: " fmt
@@ -379,9 +381,47 @@ static struct notifier_block vmware_pv_reboot_nb = {
 	.notifier_call = vmware_pv_reboot_notify,
 };
 
+/*
+ * Map per-CPU variables for all possible CPUs as decrypted.
+ * Do this early in boot, before sharing the corresponding
+ * guest physical addresses with the hypervisor.
+ */
+static void __init set_shared_memory_decrypted(void)
+{
+	int cpu;
+
+	if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+		return;
+
+	for_each_possible_cpu(cpu) {
+		unsigned long size = sizeof(vmw_steal_time);
+		unsigned long addr = (unsigned long)&per_cpu(vmw_steal_time,
+							cpu);
+
+		/*
+		 * There is no generic high-level API to mark memory as
+		 * decrypted. Intel's set_memory_decrypted() depends on the
+		 * buddy allocator and can fail early in boot if a page split
+		 * is required and allocation is not possible. Use AMD's
+		 * early_set_memory_decrypted() instead, which can perform
+		 * the split during early boot.
+		 */
+		early_set_memory_decrypted(addr, size);
+
+		/* That's it for AMD */
+		if (cc_vendor == CC_VENDOR_AMD)
+			continue;
+
+		set_memory_decrypted(addr & PAGE_MASK, 1UL <<
+				     get_order((addr & ~PAGE_MASK) + size));
+
+	}
+}
+
 #ifdef CONFIG_SMP
 static void __init vmware_smp_prepare_boot_cpu(void)
 {
+	set_shared_memory_decrypted();
 	vmware_guest_cpu_init();
 	native_smp_prepare_boot_cpu();
 }
@@ -444,6 +484,7 @@ static void __init vmware_paravirt_ops_setup(void)
 					      vmware_cpu_down_prepare) < 0)
 			pr_err("vmware_guest: Failed to install cpu hotplug callbacks\n");
 #else
+		set_shared_memory_decrypted();
 		vmware_guest_cpu_init();
 #endif
 	}
-- 
2.43.7