diff mbox series

[v10,07/50] x86/sev: Add RMP entry lookup helpers

Message ID 20231016132819.1002933-8-michael.roth@amd.com (mailing list archive)
State New, archived
Headers show
Series Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support | expand

Commit Message

Michael Roth Oct. 16, 2023, 1:27 p.m. UTC
From: Brijesh Singh <brijesh.singh@amd.com>

The snp_lookup_page_in_rmptable() can be used by the host to read the RMP
entry for a given page. The RMP entry format is documented in AMD PPR, see
https://bugzilla.kernel.org/attachment.cgi?id=296015.

Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
[mdr: separate 'assigned' indicator from return code]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 arch/x86/include/asm/sev-common.h |  4 +++
 arch/x86/include/asm/sev-host.h   | 22 +++++++++++++
 arch/x86/virt/svm/sev.c           | 53 +++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+)
 create mode 100644 arch/x86/include/asm/sev-host.h

Comments

Borislav Petkov Nov. 14, 2023, 2:24 p.m. UTC | #1
On Mon, Oct 16, 2023 at 08:27:36AM -0500, Michael Roth wrote:
> From: Brijesh Singh <brijesh.singh@amd.com>
> 
> The snp_lookup_page_in_rmptable() can be used by the host to read the RMP

$ git grep snp_lookup_page_in_rmptable
$

Stale commit message. And not very telling. Please rewrite.

> entry for a given page. The RMP entry format is documented in AMD PPR, see
> https://bugzilla.kernel.org/attachment.cgi?id=296015.

<--- Brijesh's SOB comes first here if he's the primary author.

> Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> [mdr: separate 'assigned' indicator from return code]
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
>  arch/x86/include/asm/sev-common.h |  4 +++
>  arch/x86/include/asm/sev-host.h   | 22 +++++++++++++
>  arch/x86/virt/svm/sev.c           | 53 +++++++++++++++++++++++++++++++
>  3 files changed, 79 insertions(+)
>  create mode 100644 arch/x86/include/asm/sev-host.h
> 
> diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
> index b463fcbd4b90..1e6fb93d8ab0 100644
> --- a/arch/x86/include/asm/sev-common.h
> +++ b/arch/x86/include/asm/sev-common.h
> @@ -173,4 +173,8 @@ struct snp_psc_desc {
>  #define GHCB_ERR_INVALID_INPUT		5
>  #define GHCB_ERR_INVALID_EVENT		6
>  
> +/* RMP page size */
> +#define RMP_PG_SIZE_4K			0

RMP_PG_LEVEL_4K just like the generic ones.

> +#define RMP_TO_X86_PG_LEVEL(level)	(((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)

What else is there besides X86 PG level?

IOW, RMP_TO_PG_LEVEL simply.

> +
>  #endif
> diff --git a/arch/x86/include/asm/sev-host.h b/arch/x86/include/asm/sev-host.h

Nah, we don't need a third sev header:

arch/x86/include/asm/sev-common.h
arch/x86/include/asm/sev.h
arch/x86/include/asm/sev-host.h

Put it in sev.h pls.

sev-common.h should be merged into sev.h too unless there's a compelling
reason not to which I don't see atm.

> new file mode 100644
> index 000000000000..4c487ce8457f
> --- /dev/null
> +++ b/arch/x86/include/asm/sev-host.h

...

> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index 8b9ed72489e4..7d3802605376 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -53,6 +53,9 @@ struct rmpentry {
>   */
>  #define RMPTABLE_CPU_BOOKKEEPING_SZ	0x4000
>  
> +/* Mask to apply to a PFN to get the first PFN of a 2MB page */
> +#define PFN_PMD_MASK	(~((1ULL << (PMD_SHIFT - PAGE_SHIFT)) - 1))

GENMASK_ULL

>  static struct rmpentry *rmptable_start __ro_after_init;
>  static u64 rmptable_max_pfn __ro_after_init;
>  
> @@ -237,3 +240,53 @@ static int __init snp_rmptable_init(void)
>   * the page(s) used for DMA are hypervisor owned.
>   */
>  fs_initcall(snp_rmptable_init);
> +
> +static int rmptable_entry(u64 pfn, struct rmpentry *entry)

The signature of this one should be:

static struct rmpentry *get_rmp_entry(u64 pfn)

and the callers should use the IS_ERR* macros to check whether it
returns a valid pointer or a negative value for error.

Ditto for the other two functions here.

> +	if (WARN_ON_ONCE(pfn > rmptable_max_pfn))
> +		return -EFAULT;
> +
> +	*entry = rmptable_start[pfn];

This wants to be called rmptable[] then.

> +
> +	return 0;
> +}
> +
> +static int __snp_lookup_rmpentry(u64 pfn, struct rmpentry *entry, int *level)
> +{
> +	struct rmpentry large_entry;
> +	int ret;
> +
> +	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> +		return -ENXIO;

ENODEV or so.

> +
> +	ret = rmptable_entry(pfn, entry);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Find the authoritative RMP entry for a PFN. This can be either a 4K
> +	 * RMP entry or a special large RMP entry that is authoritative for a
> +	 * whole 2M area.
> +	 */
> +	ret = rmptable_entry(pfn & PFN_PMD_MASK, &large_entry);
> +	if (ret)
> +		return ret;
> +
> +	*level = RMP_TO_X86_PG_LEVEL(large_entry.pagesize);
> +
> +	return 0;
> +}
> +
> +int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level)
> +{
> +	struct rmpentry e;
> +	int ret;
> +
> +	ret = __snp_lookup_rmpentry(pfn, &e, level);
> +	if (ret)
> +		return ret;
> +
> +	*assigned = !!e.assigned;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
> -- 

Thx.
Michael Roth Dec. 19, 2023, 3:31 a.m. UTC | #2
On Tue, Nov 14, 2023 at 03:24:42PM +0100, Borislav Petkov wrote:
> On Mon, Oct 16, 2023 at 08:27:36AM -0500, Michael Roth wrote:
> > From: Brijesh Singh <brijesh.singh@amd.com>
> > 
> > The snp_lookup_page_in_rmptable() can be used by the host to read the RMP
> 
> $ git grep snp_lookup_page_in_rmptable
> $
> 
> Stale commit message. And not very telling. Please rewrite.
> 
> > entry for a given page. The RMP entry format is documented in AMD PPR, see
> > https://bugzilla.kernel.org/attachment.cgi?id=296015.
> 
> <--- Brijesh's SOB comes first here if he's the primary author.
> 
> > Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
> > Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> > [mdr: separate 'assigned' indicator from return code]
> > Signed-off-by: Michael Roth <michael.roth@amd.com>
> > ---
> >  arch/x86/include/asm/sev-common.h |  4 +++
> >  arch/x86/include/asm/sev-host.h   | 22 +++++++++++++
> >  arch/x86/virt/svm/sev.c           | 53 +++++++++++++++++++++++++++++++
> >  3 files changed, 79 insertions(+)
> >  create mode 100644 arch/x86/include/asm/sev-host.h
> > 
> > diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
> > index b463fcbd4b90..1e6fb93d8ab0 100644
> > --- a/arch/x86/include/asm/sev-common.h
> > +++ b/arch/x86/include/asm/sev-common.h
> > @@ -173,4 +173,8 @@ struct snp_psc_desc {
> >  #define GHCB_ERR_INVALID_INPUT		5
> >  #define GHCB_ERR_INVALID_EVENT		6
> >  
> > +/* RMP page size */
> > +#define RMP_PG_SIZE_4K			0
> 
> RMP_PG_LEVEL_4K just like the generic ones.

I've moved this to sev.h, but it RMP_PG_SIZE_4K is already defined there
and used by a bunch of guest code so it's a bit out-of-place to update
those as part of this patchset. I can send a follow-up series to clean up
some of the naming and get rid of sev-common.h

> 
> > +#define RMP_TO_X86_PG_LEVEL(level)	(((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
> 
> What else is there besides X86 PG level?
> 
> IOW, RMP_TO_PG_LEVEL simply.

Make sense.

> 
> > +
> >  #endif
> > diff --git a/arch/x86/include/asm/sev-host.h b/arch/x86/include/asm/sev-host.h
> 
> Nah, we don't need a third sev header:
> 
> arch/x86/include/asm/sev-common.h
> arch/x86/include/asm/sev.h
> arch/x86/include/asm/sev-host.h
> 
> Put it in sev.h pls.

Done.

> 
> sev-common.h should be merged into sev.h too unless there's a compelling
> reason not to which I don't see atm.

Doesn't seem like it would be an issue, maybe some fallout from any
files that previously only included sev-common.h and now need to pull in
guest struct definitions as well, but those definitions don't have a lot
of external dependencies so don't anticipate any header include
hellishness. I'll send that as a separate follow-up, along with some of
the renames you suggested above since they'll touch guest code and
create unecessary churn for SNP host support.

Thanks,

Mike

> > -- 
> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette
Borislav Petkov Jan. 9, 2024, 10:07 p.m. UTC | #3
On Mon, Dec 18, 2023 at 09:31:50PM -0600, Michael Roth wrote:
> I've moved this to sev.h, but it RMP_PG_SIZE_4K is already defined there
> and used by a bunch of guest code so it's a bit out-of-place to update
> those as part of this patchset. I can send a follow-up series to clean up
> some of the naming and get rid of sev-common.h

Yap, good idea.

> Doesn't seem like it would be an issue, maybe some fallout from any
> files that previously only included sev-common.h and now need to pull in
> guest struct definitions as well, but those definitions don't have a lot
> of external dependencies so don't anticipate any header include
> hellishness. I'll send that as a separate follow-up, along with some of
> the renames you suggested above since they'll touch guest code and
> create unecessary churn for SNP host support.

OTOH, people recently have started looking at including only that stuff
which is really used so having a single header would cause more
preprocessing effort. I'm not too crazy about it as the preprocessing
overhead is barely measurable so might as well have a single header and
then split it later...

Definitely something for the after-burner and not important right now.

Thx.
diff mbox series

Patch

diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index b463fcbd4b90..1e6fb93d8ab0 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -173,4 +173,8 @@  struct snp_psc_desc {
 #define GHCB_ERR_INVALID_INPUT		5
 #define GHCB_ERR_INVALID_EVENT		6
 
+/* RMP page size */
+#define RMP_PG_SIZE_4K			0
+#define RMP_TO_X86_PG_LEVEL(level)	(((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
+
 #endif
diff --git a/arch/x86/include/asm/sev-host.h b/arch/x86/include/asm/sev-host.h
new file mode 100644
index 000000000000..4c487ce8457f
--- /dev/null
+++ b/arch/x86/include/asm/sev-host.h
@@ -0,0 +1,22 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * AMD SVM-SEV Host Support.
+ *
+ * Copyright (C) 2023 Advanced Micro Devices, Inc.
+ *
+ * Author: Ashish Kalra <ashish.kalra@amd.com>
+ *
+ */
+
+#ifndef __ASM_X86_SEV_HOST_H
+#define __ASM_X86_SEV_HOST_H
+
+#include <asm/sev-common.h>
+
+#ifdef CONFIG_KVM_AMD_SEV
+int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level);
+#else
+static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENXIO; }
+#endif
+
+#endif
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 8b9ed72489e4..7d3802605376 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -53,6 +53,9 @@  struct rmpentry {
  */
 #define RMPTABLE_CPU_BOOKKEEPING_SZ	0x4000
 
+/* Mask to apply to a PFN to get the first PFN of a 2MB page */
+#define PFN_PMD_MASK	(~((1ULL << (PMD_SHIFT - PAGE_SHIFT)) - 1))
+
 static struct rmpentry *rmptable_start __ro_after_init;
 static u64 rmptable_max_pfn __ro_after_init;
 
@@ -237,3 +240,53 @@  static int __init snp_rmptable_init(void)
  * the page(s) used for DMA are hypervisor owned.
  */
 fs_initcall(snp_rmptable_init);
+
+static int rmptable_entry(u64 pfn, struct rmpentry *entry)
+{
+	if (WARN_ON_ONCE(pfn > rmptable_max_pfn))
+		return -EFAULT;
+
+	*entry = rmptable_start[pfn];
+
+	return 0;
+}
+
+static int __snp_lookup_rmpentry(u64 pfn, struct rmpentry *entry, int *level)
+{
+	struct rmpentry large_entry;
+	int ret;
+
+	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+		return -ENXIO;
+
+	ret = rmptable_entry(pfn, entry);
+	if (ret)
+		return ret;
+
+	/*
+	 * Find the authoritative RMP entry for a PFN. This can be either a 4K
+	 * RMP entry or a special large RMP entry that is authoritative for a
+	 * whole 2M area.
+	 */
+	ret = rmptable_entry(pfn & PFN_PMD_MASK, &large_entry);
+	if (ret)
+		return ret;
+
+	*level = RMP_TO_X86_PG_LEVEL(large_entry.pagesize);
+
+	return 0;
+}
+
+int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level)
+{
+	struct rmpentry e;
+	int ret;
+
+	ret = __snp_lookup_rmpentry(pfn, &e, level);
+	if (ret)
+		return ret;
+
+	*assigned = !!e.assigned;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);