Re: [RFC v2 28/32] x86/tdx: Make pages shared in ioremap()
From: Kuppuswamy, Sathyanarayanan
Date: Tue May 25 2021 - 14:21:33 EST
Hi,
On 5/21/21 2:14 PM, Tom Lendacky wrote:
On 5/21/21 1:49 PM, Borislav Petkov wrote:
On Fri, May 21, 2021 at 11:19:15AM -0500, Tom Lendacky wrote:
In arch/x86/mm/mem_encrypt.c, sme_early_init() (should have renamed that
when SEV support was added), we do:
if (sev_active())
swiotlb_force = SWIOTLB_FORCE;
TDX should be able to do a similar thing without having to touch
arch/x86/kernel/pci-swiotlb.c.
That would remove any confusion over SME being part of a
protected_guest_has() call.
Even better.
I kinda like the separate function, though.
Only if you clean it up and get rid of the inverted logic and drop that
silly switch-case.
Except mem_encrypt_active() covers both SME and SEV, so
protected_guest_has() would be confusing.
I don't understand - the AMD-specific function amd_protected_guest_has()
would return sme_me_mask just like mem_encrypt_active() does and we can
get rid of latter.
Or do you have a problem with the name protected_guest_has() containing
"guest" while we're talking about SME here?
The latter.
If so, feel free to suggest a better one - the name does not have to
have "guest" in it.
Let me see if I can come up with something that will make sense.
Thanks,
Tom
Thx.
Following is the sample implementation. Please let me know your
comments.
tdx: Introduce generic protected_guest abstraction
Add a generic way to check if we run with an encrypted guest,
without requiring x86 specific ifdefs. This can then be used in
non architecture specific code.
is_protected_guest() helper function can be implemented using
arch specific CPU feature flags.
protected_guest_has() is used to check for protected guest
feature flags.
Originally-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
diff --git a/arch/Kconfig b/arch/Kconfig
index ecfd3520b676..98c30312555b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -956,6 +956,9 @@ config HAVE_ARCH_NVRAM_OPS
config ISA_BUS_API
def_bool ISA
+config ARCH_HAS_PROTECTED_GUEST
+ bool
+
#
# ABI hall of shame
#
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index bc91c4aa7ce4..2f31613be965 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -879,6 +879,7 @@ config INTEL_TDX_GUEST
select X86_X2APIC
select SECURITY_LOCKDOWN_LSM
select X86_MEM_ENCRYPT_COMMON
+ select ARCH_HAS_PROTECTED_GUEST
help
Provide support for running in a trusted domain on Intel processors
equipped with Trusted Domain eXtenstions. TDX is a new Intel
diff --git a/arch/x86/include/asm/protected_guest.h b/arch/x86/include/asm/protected_guest.h
new file mode 100644
index 000000000000..b2838e58ce94
--- /dev/null
+++ b/arch/x86/include/asm/protected_guest.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2020 Intel Corporation */
+#ifndef _ASM_PROTECTED_GUEST
+#define _ASM_PROTECTED_GUEST 1
+
+#include <asm/cpufeature.h>
+#include <asm/tdx.h>
+
+/* Only include through linux/protected_guest.h */
+
+static inline bool is_protected_guest(void)
+{
+ return boot_cpu_has(X86_FEATURE_TDX_GUEST);
+}
+
+static inline bool protected_guest_has(unsigned long flag)
+{
+ if (boot_cpu_has(X86_FEATURE_TDX_GUEST))
+ return tdx_protected_guest_has(flag);
+
+ return false;
+}
+
+#endif
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 175cebb7bf94..d894111f49ea 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -147,6 +147,7 @@ do { \
extern phys_addr_t tdg_shared_mask(void);
extern int tdx_hcall_gpa_intent(phys_addr_t gpa, int numpages,
enum tdx_map_type map_type);
+bool tdx_protected_guest_has(unsigned long flag);
#else // !CONFIG_INTEL_TDX_GUEST
@@ -167,6 +168,11 @@ static inline int tdx_hcall_gpa_intent(phys_addr_t gpa, int numpages,
{
return -ENODEV;
}
+
+static inline bool tdx_protected_guest_has(unsigned long flag)
+{
+ return false;
+}
#endif /* CONFIG_INTEL_TDX_GUEST */
#ifdef CONFIG_INTEL_TDX_GUEST_KVM
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index c613c89d0d6a..cbb893412b43 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -11,6 +11,7 @@
#include <linux/sched/signal.h> /* force_sig_fault() */
#include <linux/swiotlb.h>
#include <linux/security.h>
+#include <linux/protected_guest.h>
#include <linux/cpu.h>
@@ -122,6 +123,23 @@ bool is_tdx_guest(void)
}
EXPORT_SYMBOL_GPL(is_tdx_guest);
+bool tdx_protected_guest_has(unsigned long flag)
+{
+ if (!is_tdx_guest())
+ return false;
+
+ switch (flag) {
+ case VM_MEM_ENCRYPT:
+ case VM_MEM_ENCRYPT_ACTIVE:
+ case VM_UNROLL_STRING_IO:
+ case VM_HOST_MEM_ENCRYPT:
+ return true;
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(tdx_protected_guest_has);
+
/* The highest bit of a guest physical address is the "sharing" bit */
phys_addr_t tdg_shared_mask(void)
{
diff --git a/include/linux/protected_guest.h b/include/linux/protected_guest.h
new file mode 100644
index 000000000000..f362eea39bd8
--- /dev/null
+++ b/include/linux/protected_guest.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _LINUX_PROTECTED_GUEST_H
+#define _LINUX_PROTECTED_GUEST_H 1
+
+/* Protected Guest Feature Flags (leave 0-0xff for arch specific flags) */
+
+/* Support for guest encryption */
+#define VM_MEM_ENCRYPT 0x100
+/* Encryption support is active */
+#define VM_MEM_ENCRYPT_ACTIVE 0x101
+/* Support for unrolled string IO */
+#define VM_UNROLL_STRING_IO 0x102
+/* Support for host memory encryption */
+#define VM_HOST_MEM_ENCRYPT 0x103
+
+#ifdef CONFIG_ARCH_HAS_PROTECTED_GUEST
+#include <asm/protected_guest.h>
+#else
+static inline bool is_protected_guest(void) { return false; }
+static inline bool protected_guest_has(unsigned long flag) { return false; }
+#endif
+
+#endif
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer