diff mbox series

[01/11] mm: Introduce a function to check for virtualization protection features

Message ID cbc875b1d2113225c2b44a2384d5b303d0453cf7.1627424774.git.thomas.lendacky@amd.com (mailing list archive)
State New
Headers show
Series Implement generic prot_guest_has() helper function | expand

Commit Message

Tom Lendacky July 27, 2021, 10:26 p.m. UTC
In prep for other protected virtualization technologies, introduce a
generic helper function, prot_guest_has(), that can be used to check
for specific protection attributes, like memory encryption. This is
intended to eliminate having to add multiple technology-specific checks
to the code (e.g. if (sev_active() || tdx_active())).

Co-developed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/Kconfig                    |  3 +++
 include/linux/protected_guest.h | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 include/linux/protected_guest.h

Comments

Christoph Hellwig July 28, 2021, 1:17 p.m. UTC | #1
On Tue, Jul 27, 2021 at 05:26:04PM -0500, Tom Lendacky via iommu wrote:
> In prep for other protected virtualization technologies, introduce a
> generic helper function, prot_guest_has(), that can be used to check
> for specific protection attributes, like memory encryption. This is
> intended to eliminate having to add multiple technology-specific checks
> to the code (e.g. if (sev_active() || tdx_active())).

So common checks obviously make sense, but I really hate the stupid
multiplexer.  Having one well-documented helper per feature is much
easier to follow.

> +#define PATTR_MEM_ENCRYPT		0	/* Encrypted memory */
> +#define PATTR_HOST_MEM_ENCRYPT		1	/* Host encrypted memory */
> +#define PATTR_GUEST_MEM_ENCRYPT		2	/* Guest encrypted memory */
> +#define PATTR_GUEST_PROT_STATE		3	/* Guest encrypted state */

The kerneldoc comments on these individual helpers will give you plenty
of space to properly document what they indicate and what a (potential)
caller should do based on them.  Something the above comments completely
fail to.
Borislav Petkov July 28, 2021, 4:28 p.m. UTC | #2
On Wed, Jul 28, 2021 at 02:17:27PM +0100, Christoph Hellwig wrote:
> So common checks obviously make sense, but I really hate the stupid
> multiplexer.  Having one well-documented helper per feature is much
> easier to follow.

We had that in x86 - it was called cpu_has_<xxx> where xxx is the
feature bit. It didn't scale with the sheer amount of feature bits that
kept getting added so we do cpu_feature_enabled(X86_FEATURE_XXX) now.

The idea behind this is very similar - those protected guest flags
will only grow in the couple of tens range - at least - so having a
multiplexer is a lot simpler, I'd say, than having a couple of tens of
helpers. And those PATTR flags should have good, readable names, btw.

Thx.
Joerg Roedel Aug. 2, 2021, 10:34 a.m. UTC | #3
On Tue, Jul 27, 2021 at 05:26:04PM -0500, Tom Lendacky wrote:
> In prep for other protected virtualization technologies, introduce a
> generic helper function, prot_guest_has(), that can be used to check
> for specific protection attributes, like memory encryption. This is
> intended to eliminate having to add multiple technology-specific checks
> to the code (e.g. if (sev_active() || tdx_active())).
> 
> Co-developed-by: Andi Kleen <ak@linux.intel.com>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>

Reviewed-by: Joerg Roedel <jroedel@suse.de>
Kuppuswamy, Sathyanarayanan Aug. 11, 2021, 2:53 p.m. UTC | #4
On 7/27/21 3:26 PM, Tom Lendacky wrote:
> diff --git a/include/linux/protected_guest.h b/include/linux/protected_guest.h
> new file mode 100644
> index 000000000000..f8ed7b72967b
> --- /dev/null
> +++ b/include/linux/protected_guest.h
> @@ -0,0 +1,32 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Protected Guest (and Host) Capability checks
> + *
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Tom Lendacky<thomas.lendacky@amd.com>
> + */
> +
> +#ifndef _PROTECTED_GUEST_H
> +#define _PROTECTED_GUEST_H
> +
> +#ifndef __ASSEMBLY__

Can you include headers for bool type and false definition?

--- a/include/linux/protected_guest.h
+++ b/include/linux/protected_guest.h
@@ -12,6 +12,9 @@

  #ifndef __ASSEMBLY__

+#include <linux/types.h>
+#include <linux/stddef.h>

Otherwise, I see following errors in multi-config auto testing.

include/linux/protected_guest.h:40:15: error: unknown type name 'bool'
include/linux/protected_guest.h:40:63: error: 'false' undeclared (first use in this functi


> +
> +#define PATTR_MEM_ENCRYPT		0	/* Encrypted memory */
> +#define PATTR_HOST_MEM_ENCRYPT		1	/* Host encrypted memory */
> +#define PATTR_GUEST_MEM_ENCRYPT		2	/* Guest encrypted memory */
> +#define PATTR_GUEST_PROT_STATE		3	/* Guest encrypted state */
> +
> +#ifdef CONFIG_ARCH_HAS_PROTECTED_GUEST
> +
> +#include <asm/protected_guest.h>
> +
> +#else	/* !CONFIG_ARCH_HAS_PROTECTED_GUEST */
> +
> +static inline bool prot_guest_has(unsigned int attr) { return false; }
> +
> +#endif	/* CONFIG_ARCH_HAS_PROTECTED_GUEST */
> +
> +#endif	/* __ASSEMBLY__ */
> +
> +#endif	/* _PROTECTED_GUEST_H */
Tom Lendacky Aug. 11, 2021, 3:39 p.m. UTC | #5
On 8/11/21 9:53 AM, Kuppuswamy, Sathyanarayanan wrote:
> On 7/27/21 3:26 PM, Tom Lendacky wrote:
>> diff --git a/include/linux/protected_guest.h
>> b/include/linux/protected_guest.h
>> new file mode 100644
>> index 000000000000..f8ed7b72967b
>> --- /dev/null
>> +++ b/include/linux/protected_guest.h
>> @@ -0,0 +1,32 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Protected Guest (and Host) Capability checks
>> + *
>> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
>> + *
>> + * Author: Tom Lendacky<thomas.lendacky@amd.com>
>> + */
>> +
>> +#ifndef _PROTECTED_GUEST_H
>> +#define _PROTECTED_GUEST_H
>> +
>> +#ifndef __ASSEMBLY__
> 
> Can you include headers for bool type and false definition?

Can do.

Thanks,
Tom

> 
> --- a/include/linux/protected_guest.h
> +++ b/include/linux/protected_guest.h
> @@ -12,6 +12,9 @@
> 
>  #ifndef __ASSEMBLY__
> 
> +#include <linux/types.h>
> +#include <linux/stddef.h>
> 
> Otherwise, I see following errors in multi-config auto testing.
> 
> include/linux/protected_guest.h:40:15: error: unknown type name 'bool'
> include/linux/protected_guest.h:40:63: error: 'false' undeclared (first
> use in this functi
>
diff mbox series

Patch

diff --git a/arch/Kconfig b/arch/Kconfig
index 129df498a8e1..a47cf283f2ff 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1231,6 +1231,9 @@  config RELR
 config ARCH_HAS_MEM_ENCRYPT
 	bool
 
+config ARCH_HAS_PROTECTED_GUEST
+	bool
+
 config HAVE_SPARSE_SYSCALL_NR
        bool
        help
diff --git a/include/linux/protected_guest.h b/include/linux/protected_guest.h
new file mode 100644
index 000000000000..f8ed7b72967b
--- /dev/null
+++ b/include/linux/protected_guest.h
@@ -0,0 +1,32 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Protected Guest (and Host) Capability checks
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@amd.com>
+ */
+
+#ifndef _PROTECTED_GUEST_H
+#define _PROTECTED_GUEST_H
+
+#ifndef __ASSEMBLY__
+
+#define PATTR_MEM_ENCRYPT		0	/* Encrypted memory */
+#define PATTR_HOST_MEM_ENCRYPT		1	/* Host encrypted memory */
+#define PATTR_GUEST_MEM_ENCRYPT		2	/* Guest encrypted memory */
+#define PATTR_GUEST_PROT_STATE		3	/* Guest encrypted state */
+
+#ifdef CONFIG_ARCH_HAS_PROTECTED_GUEST
+
+#include <asm/protected_guest.h>
+
+#else	/* !CONFIG_ARCH_HAS_PROTECTED_GUEST */
+
+static inline bool prot_guest_has(unsigned int attr) { return false; }
+
+#endif	/* CONFIG_ARCH_HAS_PROTECTED_GUEST */
+
+#endif	/* __ASSEMBLY__ */
+
+#endif	/* _PROTECTED_GUEST_H */