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[Part2,RFC,v3,06/37] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction

Message ID 20210602141057.27107-7-brijesh.singh@amd.com (mailing list archive)
State New, archived
Headers show
Series Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support | expand

Commit Message

Brijesh Singh June 2, 2021, 2:10 p.m. UTC 
The RMPUPDATE instruction writes a new RMP entry in the RMP Table. The
hypervisor will use the instruction to add pages to the RMP table. See
APM3 for details on the instruction operations.

The PSMASH instruction expands a 2MB RMP entry into a corresponding set of
contiguous 4KB-Page RMP entries. The hypervisor will use this instruction
to adjust the RMP entry without invalidating the previous RMP entry.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 arch/x86/kernel/sev.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/sev.h   | 20 ++++++++++++++++++++
 2 files changed, 62 insertions(+)

Comments

Dr. David Alan Gilbert June 10, 2021, 1:03 p.m. UTC | #1 
* Brijesh Singh (brijesh.singh@amd.com) wrote:
> The RMPUPDATE instruction writes a new RMP entry in the RMP Table. The
> hypervisor will use the instruction to add pages to the RMP table. See
> APM3 for details on the instruction operations.
> 
> The PSMASH instruction expands a 2MB RMP entry into a corresponding set of
> contiguous 4KB-Page RMP entries. The hypervisor will use this instruction
> to adjust the RMP entry without invalidating the previous RMP entry.
> 
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  arch/x86/kernel/sev.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/sev.h   | 20 ++++++++++++++++++++
>  2 files changed, 62 insertions(+)
> 
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 51676ab1a321..9727df945fb1 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -2226,3 +2226,45 @@ struct rmpentry *snp_lookup_page_in_rmptable(struct page *page, int *level)
>  	return entry;
>  }
>  EXPORT_SYMBOL_GPL(snp_lookup_page_in_rmptable);
> +
> +int psmash(struct page *page)
> +{
> +	unsigned long spa = page_to_pfn(page) << PAGE_SHIFT;
> +	int ret;
> +
> +	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> +		return -ENXIO;
> +
> +	/* Retry if another processor is modifying the RMP entry. */
> +	do {
> +		/* Binutils version 2.36 supports the PSMASH mnemonic. */
> +		asm volatile(".byte 0xF3, 0x0F, 0x01, 0xFF"
> +			      : "=a"(ret)
> +			      : "a"(spa)
> +			      : "memory", "cc");
> +	} while (ret == FAIL_INUSE);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(psmash);
> +
> +int rmpupdate(struct page *page, struct rmpupdate *val)
> +{
> +	unsigned long spa = page_to_pfn(page) << PAGE_SHIFT;
> +	int ret;
> +
> +	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> +		return -ENXIO;
> +
> +	/* Retry if another processor is modifying the RMP entry. */
> +	do {
> +		/* Binutils version 2.36 supports the RMPUPDATE mnemonic. */
> +		asm volatile(".byte 0xF2, 0x0F, 0x01, 0xFE"
> +			     : "=a"(ret)
> +			     : "a"(spa), "c"((unsigned long)val)
> +			     : "memory", "cc");
> +	} while (ret == FAIL_INUSE);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(rmpupdate);
> diff --git a/include/linux/sev.h b/include/linux/sev.h
> index 83c89e999999..bcd4d75d87c8 100644
> --- a/include/linux/sev.h
> +++ b/include/linux/sev.h
> @@ -39,13 +39,33 @@ struct __packed rmpentry {
>  
>  #define RMP_TO_X86_PG_LEVEL(level)	(((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
>  
> +struct rmpupdate {
> +	u64 gpa;
> +	u8 assigned;
> +	u8 pagesize;
> +	u8 immutable;
> +	u8 rsvd;
> +	u32 asid;
> +} __packed;
> +
> +
> +/*
> + * The psmash() and rmpupdate() returns FAIL_INUSE when another processor is
> + * modifying the RMP entry.
> + */
> +#define FAIL_INUSE              3

Perhaps SEV_FAIL_INUSE ?

(Given that there are a whole buunch of FAIL_* macros already in
general)

Dave

>  #ifdef CONFIG_AMD_MEM_ENCRYPT
>  struct rmpentry *snp_lookup_page_in_rmptable(struct page *page, int *level);
> +int psmash(struct page *page);
> +int rmpupdate(struct page *page, struct rmpupdate *e);
>  #else
>  static inline struct rmpentry *snp_lookup_page_in_rmptable(struct page *page, int *level)
>  {
>  	return NULL;
>  }
> +static inline int psmash(struct page *page) { return -ENXIO; }
> +static inline int rmpupdate(struct page *page, struct rmpupdate *e) { return -ENXIO; }
>  
>  #endif /* CONFIG_AMD_MEM_ENCRYPT */
>  #endif /* __LINUX_SEV_H */
> -- 
> 2.17.1
> 
>
diff mbox series

Patch

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 51676ab1a321..9727df945fb1 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2226,3 +2226,45 @@  struct rmpentry *snp_lookup_page_in_rmptable(struct page *page, int *level)
 	return entry;
 }
 EXPORT_SYMBOL_GPL(snp_lookup_page_in_rmptable);
+
+int psmash(struct page *page)
+{
+	unsigned long spa = page_to_pfn(page) << PAGE_SHIFT;
+	int ret;
+
+	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+		return -ENXIO;
+
+	/* Retry if another processor is modifying the RMP entry. */
+	do {
+		/* Binutils version 2.36 supports the PSMASH mnemonic. */
+		asm volatile(".byte 0xF3, 0x0F, 0x01, 0xFF"
+			      : "=a"(ret)
+			      : "a"(spa)
+			      : "memory", "cc");
+	} while (ret == FAIL_INUSE);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(psmash);
+
+int rmpupdate(struct page *page, struct rmpupdate *val)
+{
+	unsigned long spa = page_to_pfn(page) << PAGE_SHIFT;
+	int ret;
+
+	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+		return -ENXIO;
+
+	/* Retry if another processor is modifying the RMP entry. */
+	do {
+		/* Binutils version 2.36 supports the RMPUPDATE mnemonic. */
+		asm volatile(".byte 0xF2, 0x0F, 0x01, 0xFE"
+			     : "=a"(ret)
+			     : "a"(spa), "c"((unsigned long)val)
+			     : "memory", "cc");
+	} while (ret == FAIL_INUSE);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(rmpupdate);
diff --git a/include/linux/sev.h b/include/linux/sev.h
index 83c89e999999..bcd4d75d87c8 100644
--- a/include/linux/sev.h
+++ b/include/linux/sev.h
@@ -39,13 +39,33 @@  struct __packed rmpentry {
 
 #define RMP_TO_X86_PG_LEVEL(level)	(((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
 
+struct rmpupdate {
+	u64 gpa;
+	u8 assigned;
+	u8 pagesize;
+	u8 immutable;
+	u8 rsvd;
+	u32 asid;
+} __packed;
+
+
+/*
+ * The psmash() and rmpupdate() returns FAIL_INUSE when another processor is
+ * modifying the RMP entry.
+ */
+#define FAIL_INUSE              3
+
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 struct rmpentry *snp_lookup_page_in_rmptable(struct page *page, int *level);
+int psmash(struct page *page);
+int rmpupdate(struct page *page, struct rmpupdate *e);
 #else
 static inline struct rmpentry *snp_lookup_page_in_rmptable(struct page *page, int *level)
 {
 	return NULL;
 }
+static inline int psmash(struct page *page) { return -ENXIO; }
+static inline int rmpupdate(struct page *page, struct rmpupdate *e) { return -ENXIO; }
 
 #endif /* CONFIG_AMD_MEM_ENCRYPT */
 #endif /* __LINUX_SEV_H */