[PATCH 4/6] x86/sev: Add interface to re-enable RMP optimizations.

[Ashish Kalra]

From: Ashish Kalra <ashish.kalra@xxxxxxx>

RMPOPT table is a per-processor table which indicates if 1GB regions of
physical memory are entirely hypervisor-owned or not.

When performing host memory accesses in hypervisor mode as well as
non-SNP guest mode, the processor may consult the RMPOPT table to
potentially skip an RMP access and improve performance.

Events such as RMPUPDATE or SNP_INIT can clear RMP optimizations. Add
an interface to re-enable those optimizations.

Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
 arch/x86/include/asm/sev.h   |  2 ++
 arch/x86/virt/svm/sev.c      | 17 +++++++++++++++++
 drivers/crypto/ccp/sev-dev.c |  4 ++++
 3 files changed, 23 insertions(+)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 0e6c0940100f..451fb2b2a0f7 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -657,6 +657,7 @@ int rmp_make_shared(u64 pfn, enum pg_level level);
 void __snp_leak_pages(u64 pfn, unsigned int npages, bool dump_rmp);
 void kdump_sev_callback(void);
 void snp_fixup_e820_tables(void);
+int snp_perform_rmp_optimization(void);
 static inline void snp_leak_pages(u64 pfn, unsigned int pages)
 {
 	__snp_leak_pages(pfn, pages, true);
@@ -677,6 +678,7 @@ static inline void __snp_leak_pages(u64 pfn, unsigned int npages, bool dump_rmp)
 static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}
 static inline void kdump_sev_callback(void) { }
 static inline void snp_fixup_e820_tables(void) {}
+static inline int snp_perform_rmp_optimization(void) { return 0; }
 #endif
 
 #endif
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index a0d38fc50698..713afcc2fab3 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -1305,6 +1305,23 @@ int rmp_make_shared(u64 pfn, enum pg_level level)
 }
 EXPORT_SYMBOL_GPL(rmp_make_shared);
 
+int snp_perform_rmp_optimization(void)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_RMPOPT))
+		return -EINVAL;
+
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+		return -EINVAL;
+
+	if (!(rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED))
+		return -EINVAL;
+
+	rmpopt_all_physmem();
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snp_perform_rmp_optimization);
+
 void __snp_leak_pages(u64 pfn, unsigned int npages, bool dump_rmp)
 {
 	struct page *page = pfn_to_page(pfn);
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 1cdadddb744e..d3df29b0c6bf 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -1478,6 +1478,10 @@ static int __sev_snp_init_locked(int *error, unsigned int max_snp_asid)
 	}
 
 	snp_hv_fixed_pages_state_update(sev, HV_FIXED);
+
+	/* SNP_INIT clears the RMPOPT table, re-enable RMP optimizations */
+	snp_perform_rmp_optimization();
+
 	sev->snp_initialized = true;
 	dev_dbg(sev->dev, "SEV-SNP firmware initialized, SEV-TIO is %s\n",
 		data.tio_en ? "enabled" : "disabled");
-- 
2.43.0