Re: [PATCH v10 21/45] x86/mm: Add support to validate memory when changing C-bit

[Borislav Petkov <bp@alien8.de>]

On Fri, Feb 11, 2022 at 03:55:23PM +0100, Borislav Petkov wrote:
> Also, I think adding required functions to x86_platform.guest. is a very
> nice way to solve the ugly if (guest_type) querying all over the place.

So I guess something like below. It builds here...

---
 arch/x86/include/asm/set_memory.h |  1 -
 arch/x86/include/asm/sev.h        |  2 ++
 arch/x86/include/asm/x86_init.h   | 12 ++++++++++++
 arch/x86/kernel/sev.c             |  2 ++
 arch/x86/mm/mem_encrypt_amd.c     |  6 +++---
 arch/x86/mm/pat/set_memory.c      |  2 +-
 6 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index ff0f2d90338a..ce8dd215f5b3 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -84,7 +84,6 @@ int set_pages_rw(struct page *page, int numpages);
 int set_direct_map_invalid_noflush(struct page *page);
 int set_direct_map_default_noflush(struct page *page);
 bool kernel_page_present(struct page *page);
-void notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc);
 
 extern int kernel_set_to_readonly;
 
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ec060c433589..2435b0ca6cfc 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -95,4 +95,6 @@ static inline void sev_es_nmi_complete(void) { }
 static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
 #endif
 
+void amd_notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc);
+
 #endif
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 22b7412c08f6..226663e2d769 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -141,6 +141,17 @@ struct x86_init_acpi {
 	void (*reduced_hw_early_init)(void);
 };
 
+/**
+ * struct x86_guest - Functions used by misc guest incarnations like SEV, TDX,
+ * etc.
+ *
+ * @enc_status_change		Notify HV about change of encryption status of a
+ *				range of pages
+ */
+struct x86_guest {
+	void (*enc_status_change)(unsigned long vaddr, int npages, bool enc);
+};
+
 /**
  * struct x86_init_ops - functions for platform specific setup
  *
@@ -287,6 +298,7 @@ struct x86_platform_ops {
 	struct x86_legacy_features legacy;
 	void (*set_legacy_features)(void);
 	struct x86_hyper_runtime hyper;
+	struct x86_guest guest;
 };
 
 struct x86_apic_ops {
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index e6d316a01fdd..e645e868a49b 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -766,6 +766,8 @@ void __init sev_es_init_vc_handling(void)
 	if (!sev_es_check_cpu_features())
 		panic("SEV-ES CPU Features missing");
 
+	x86_platform.guest.enc_status_change = amd_notify_range_enc_status_changed;
+
 	/* Enable SEV-ES special handling */
 	static_branch_enable(&sev_es_enable_key);
 
diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index 2b2d018ea345..7038a9f7ae55 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -256,7 +256,7 @@ static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
 	return pfn;
 }
 
-void notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc)
+void amd_notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc)
 {
 #ifdef CONFIG_PARAVIRT
 	unsigned long sz = npages << PAGE_SHIFT;
@@ -392,7 +392,7 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
 	ret = 0;
 
-	notify_range_enc_status_changed(start, PAGE_ALIGN(size) >> PAGE_SHIFT, enc);
+	amd_notify_range_enc_status_changed(start, PAGE_ALIGN(size) >> PAGE_SHIFT, enc);
 out:
 	__flush_tlb_all();
 	return ret;
@@ -410,7 +410,7 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
 
 void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, bool enc)
 {
-	notify_range_enc_status_changed(vaddr, npages, enc);
+	amd_notify_range_enc_status_changed(vaddr, npages, enc);
 }
 
 void __init mem_encrypt_free_decrypted_mem(void)
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index b4072115c8ef..0acc52a3a5b7 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -2027,7 +2027,7 @@ static int __set_memory_enc_pgtable(unsigned long addr, int numpages, bool enc)
 	 * Notify hypervisor that a given memory range is mapped encrypted
 	 * or decrypted.
 	 */
-	notify_range_enc_status_changed(addr, numpages, enc);
+	x86_platform.guest.enc_status_change(addr, numpages, enc);
 
 	return ret;
 }
-- 
2.29.2

-- 
Regards/Gruss,
    Boris.

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