diff mbox series

[RFC,v9,19/51] x86/sev: Introduce snp leaked pages list

Message ID 20230612042559.375660-20-michael.roth@amd.com (mailing list archive)
State New
Headers show
Series Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support | expand

Commit Message

Michael Roth June 12, 2023, 4:25 a.m. UTC 
From: Ashish Kalra <ashish.kalra@amd.com>

Pages are unsafe to be released back to the page-allocator, if they
have been transitioned to firmware/guest state and can't be reclaimed
or transitioned back to hypervisor/shared state. In this case add
them to an internal leaked pages list to ensure that they are not freed
or touched/accessed to cause fatal page faults.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
[mdr: relocate to arch/x86/coco/sev/host.c]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 arch/x86/coco/sev/host.c        | 28 ++++++++++++++++++++++++++++
 arch/x86/include/asm/sev-host.h |  3 +++
 2 files changed, 31 insertions(+)

Comments

Jeremi Piotrowski Aug. 9, 2023, 12:46 p.m. UTC | #1 
On Sun, Jun 11, 2023 at 11:25:27PM -0500, Michael Roth wrote:
> From: Ashish Kalra <ashish.kalra@amd.com>
> 
> Pages are unsafe to be released back to the page-allocator, if they
> have been transitioned to firmware/guest state and can't be reclaimed
> or transitioned back to hypervisor/shared state. In this case add
> them to an internal leaked pages list to ensure that they are not freed
> or touched/accessed to cause fatal page faults.
> 
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> [mdr: relocate to arch/x86/coco/sev/host.c]
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
>  arch/x86/coco/sev/host.c        | 28 ++++++++++++++++++++++++++++
>  arch/x86/include/asm/sev-host.h |  3 +++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/arch/x86/coco/sev/host.c b/arch/x86/coco/sev/host.c
> index cd3b4c6a25bc..373e91f5a337 100644
> --- a/arch/x86/coco/sev/host.c
> +++ b/arch/x86/coco/sev/host.c
> @@ -64,6 +64,12 @@ struct rmpentry {
>  static unsigned long rmptable_start __ro_after_init;
>  static unsigned long rmptable_end __ro_after_init;
>  
> +/* list of pages which are leaked and cannot be reclaimed */
> +static LIST_HEAD(snp_leaked_pages_list);
> +static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
> +
> +static atomic_long_t snp_nr_leaked_pages = ATOMIC_LONG_INIT(0);
> +
>  #undef pr_fmt
>  #define pr_fmt(fmt)	"SEV-SNP: " fmt
>  
> @@ -494,3 +500,25 @@ int rmp_make_shared(u64 pfn, enum pg_level level)
>  	return rmpupdate(pfn, &val);
>  }
>  EXPORT_SYMBOL_GPL(rmp_make_shared);
> +
> +void snp_leak_pages(unsigned long pfn, unsigned int npages)
> +{
> +	struct page *page = pfn_to_page(pfn);
> +
> +	WARN(1, "psc failed, pfn 0x%lx pages %d (marked offline)\n", pfn, npages);
> +
> +	spin_lock(&snp_leaked_pages_list_lock);
> +	while (npages--) {
> +		/*
> +		 * Reuse the page's buddy list for chaining into the leaked
> +		 * pages list. This page should not be on a free list currently
> +		 * and is also unsafe to be added to a free list.
> +		 */
> +		list_add_tail(&page->buddy_list, &snp_leaked_pages_list);
> +		sev_dump_rmpentry(pfn);
> +		pfn++;
> +	}
> +	spin_unlock(&snp_leaked_pages_list_lock);
> +	atomic_long_inc(&snp_nr_leaked_pages);
> +}
> +EXPORT_SYMBOL_GPL(snp_leak_pages);
> diff --git a/arch/x86/include/asm/sev-host.h b/arch/x86/include/asm/sev-host.h
> index 753e80d16433..bab3b226777a 100644
> --- a/arch/x86/include/asm/sev-host.h
> +++ b/arch/x86/include/asm/sev-host.h
> @@ -19,6 +19,8 @@ void sev_dump_rmpentry(u64 pfn);
>  int psmash(u64 pfn);
>  int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable);
>  int rmp_make_shared(u64 pfn, enum pg_level level);
> +void snp_leak_pages(unsigned long pfn, unsigned int npages);
> +
>  #else
>  static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return 0; }
>  static inline void sev_dump_rmpentry(u64 pfn) {}
> @@ -29,6 +31,7 @@ static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int as
>  	return -ENODEV;
>  }
>  static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
> +void snp_leak_pages(unsigned long pfn, unsigned int npages) {}

This needs to be 'static inline' or the build fails with multiple definition errors.
I'm building a guest kernel with CONFIG_KVM_AMD_SEV disabled.

Jeremi

>  #endif
>  
>  #endif
> -- 
> 2.25.1
>
diff mbox series

Patch

diff --git a/arch/x86/coco/sev/host.c b/arch/x86/coco/sev/host.c
index cd3b4c6a25bc..373e91f5a337 100644
--- a/arch/x86/coco/sev/host.c
+++ b/arch/x86/coco/sev/host.c
@@ -64,6 +64,12 @@  struct rmpentry {
 static unsigned long rmptable_start __ro_after_init;
 static unsigned long rmptable_end __ro_after_init;
 
+/* list of pages which are leaked and cannot be reclaimed */
+static LIST_HEAD(snp_leaked_pages_list);
+static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
+
+static atomic_long_t snp_nr_leaked_pages = ATOMIC_LONG_INIT(0);
+
 #undef pr_fmt
 #define pr_fmt(fmt)	"SEV-SNP: " fmt
 
@@ -494,3 +500,25 @@  int rmp_make_shared(u64 pfn, enum pg_level level)
 	return rmpupdate(pfn, &val);
 }
 EXPORT_SYMBOL_GPL(rmp_make_shared);
+
+void snp_leak_pages(unsigned long pfn, unsigned int npages)
+{
+	struct page *page = pfn_to_page(pfn);
+
+	WARN(1, "psc failed, pfn 0x%lx pages %d (marked offline)\n", pfn, npages);
+
+	spin_lock(&snp_leaked_pages_list_lock);
+	while (npages--) {
+		/*
+		 * Reuse the page's buddy list for chaining into the leaked
+		 * pages list. This page should not be on a free list currently
+		 * and is also unsafe to be added to a free list.
+		 */
+		list_add_tail(&page->buddy_list, &snp_leaked_pages_list);
+		sev_dump_rmpentry(pfn);
+		pfn++;
+	}
+	spin_unlock(&snp_leaked_pages_list_lock);
+	atomic_long_inc(&snp_nr_leaked_pages);
+}
+EXPORT_SYMBOL_GPL(snp_leak_pages);
diff --git a/arch/x86/include/asm/sev-host.h b/arch/x86/include/asm/sev-host.h
index 753e80d16433..bab3b226777a 100644
--- a/arch/x86/include/asm/sev-host.h
+++ b/arch/x86/include/asm/sev-host.h
@@ -19,6 +19,8 @@  void sev_dump_rmpentry(u64 pfn);
 int psmash(u64 pfn);
 int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable);
 int rmp_make_shared(u64 pfn, enum pg_level level);
+void snp_leak_pages(unsigned long pfn, unsigned int npages);
+
 #else
 static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return 0; }
 static inline void sev_dump_rmpentry(u64 pfn) {}
@@ -29,6 +31,7 @@  static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int as
 	return -ENODEV;
 }
 static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
+void snp_leak_pages(unsigned long pfn, unsigned int npages) {}
 #endif
 
 #endif