Subject: Re: [PATCH V2 03/14] x86/set_memory: Add x86_set_memory_enc static call support

From: Tianyu Lan <[email-masked]>
Date: Thu, 5 Aug 2021 22:05:17 +0800

Hi Dave:
	Thanks for review.

On 8/5/2021 3:27 AM, Dave Hansen wrote:
> On 8/4/21 11:44 AM, Tianyu Lan wrote:
>> +static int default_set_memory_enc(unsigned long addr, int numpages, bool enc);
>> +DEFINE_STATIC_CALL(x86_set_memory_enc, default_set_memory_enc);
>> +
>>   #define CPA_FLUSHTLB 1
>>   #define CPA_ARRAY 2
>>   #define CPA_PAGES_ARRAY 4
>> @@ -1981,6 +1985,11 @@ int set_memory_global(unsigned long addr, int numpages)
>>   }
>>   
>>   static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
>> +{
>> +	return static_call(x86_set_memory_enc)(addr, numpages, enc);
>> +}
>> +
>> +static int default_set_memory_enc(unsigned long addr, int numpages, bool enc)
>>   {
>>   	struct cpa_data cpa;
>>   	int ret;
> 
> It doesn't make a lot of difference to add this infrastructure and then
> ignore it for the existing in-tree user:
> 
>> static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
>> {
>>          struct cpa_data cpa;
>>          int ret;
>>
>>          /* Nothing to do if memory encryption is not active */
>>          if (!mem_encrypt_active())
>>                  return 0;
> 
> Shouldn't the default be to just "return 0"?  Then on
> mem_encrypt_active() systems, do the bulk of what is in
> __set_memory_enc_dec() today.
> 

OK. I try moving code in __set_memory_enc_dec() to sev file 
mem_encrypt.c and this requires to expose cpa functions and structure.
Please have a look.

Tom, Joerg and Brijesh, Could you review at sev code change?
Thanks.

diff --git a/arch/x86/include/asm/set_memory.h 
b/arch/x86/include/asm/set_memory.h
index 43fa081a1adb..991366612deb 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -4,6 +4,25 @@

  #include <asm/page.h>
  #include <asm-generic/set_memory.h>
+#include <linux/static_call.h>
+
+/*
+ * The current flushing context - we pass it instead of 5 arguments:
+ */
+struct cpa_data {
+	unsigned long	*vaddr;
+	pgd_t		*pgd;
+	pgprot_t	mask_set;
+	pgprot_t	mask_clr;
+	unsigned long	numpages;
+	unsigned long	curpage;
+	unsigned long	pfn;
+	unsigned int	flags;
+	unsigned int	force_split		: 1,
+			force_static_prot	: 1,
+			force_flush_all		: 1;
+	struct page	**pages;
+};

  /*
   * The set_memory_* API can be used to change various attributes of a 
virtual
@@ -83,6 +102,11 @@ 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);
+int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias);
+void cpa_flush(struct cpa_data *data, int cache);
+
+int dummy_set_memory_enc(unsigned long addr, int numpages, bool enc);
+DECLARE_STATIC_CALL(x86_set_memory_enc, dummy_set_memory_enc);

  extern int kernel_set_to_readonly;

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index ff08dc463634..49e957c4191f 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -20,6 +20,8 @@
  #include <linux/bitops.h>
  #include <linux/dma-mapping.h>
  #include <linux/virtio_config.h>
+#include <linux/highmem.h>
+#include <linux/static_call.h>

  #include <asm/tlbflush.h>
  #include <asm/fixmap.h>
@@ -178,6 +180,45 @@ void __init sme_map_bootdata(char *real_mode_data)
  	__sme_early_map_unmap_mem(__va(cmdline_paddr), COMMAND_LINE_SIZE, true);
  }

+static int sev_set_memory_enc(unsigned long addr, int numpages, bool enc)
+{
+	struct cpa_data cpa;
+	int ret;
+
+	/* Should not be working on unaligned addresses */
+	if (WARN_ONCE(addr & ~PAGE_MASK, "misaligned address: %#lx\n", addr))
+		addr &= PAGE_MASK;
+
+	memset(&cpa, 0, sizeof(cpa));
+	cpa.vaddr = &addr;
+	cpa.numpages = numpages;
+	cpa.mask_set = enc ? __pgprot(_PAGE_ENC) : __pgprot(0);
+	cpa.mask_clr = enc ? __pgprot(0) : __pgprot(_PAGE_ENC);
+	cpa.pgd = init_mm.pgd;
+
+	/* Must avoid aliasing mappings in the highmem code */
+	kmap_flush_unused();
+	vm_unmap_aliases();
+
+	/*
+	 * Before changing the encryption attribute, we need to flush caches.
+	 */
+	cpa_flush(&cpa, !this_cpu_has(X86_FEATURE_SME_COHERENT));
+
+	ret = __change_page_attr_set_clr(&cpa, 1);
+
+	/*
+	 * After changing the encryption attribute, we need to flush TLBs again
+	 * in case any speculative TLB caching occurred (but no need to flush
+	 * caches again).  We could just use cpa_flush_all(), but in case TLB
+	 * flushing gets optimized in the cpa_flush() path use the same logic
+	 * as above.
+	 */
+	cpa_flush(&cpa, 0);
+
+	return ret;
+}
+
  void __init sme_early_init(void)
  {
  	unsigned int i;
@@ -185,6 +226,8 @@ void __init sme_early_init(void)
  	if (!sme_me_mask)
  		return;

+	static_call_update(x86_set_memory_enc, sev_set_memory_enc);
+
  	early_pmd_flags = __sme_set(early_pmd_flags);

  	__supported_pte_mask = __sme_set(__supported_pte_mask);
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index ad8a5c586a35..4f15f7c89dbc 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -18,6 +18,7 @@
  #include <linux/libnvdimm.h>
  #include <linux/vmstat.h>
  #include <linux/kernel.h>
+#include <linux/static_call.h>

  #include <asm/e820/api.h>
  #include <asm/processor.h>
@@ -32,24 +33,6 @@

  #include "../mm_internal.h"

-/*
- * The current flushing context - we pass it instead of 5 arguments:
- */
-struct cpa_data {
-	unsigned long	*vaddr;
-	pgd_t		*pgd;
-	pgprot_t	mask_set;
-	pgprot_t	mask_clr;
-	unsigned long	numpages;
-	unsigned long	curpage;
-	unsigned long	pfn;
-	unsigned int	flags;
-	unsigned int	force_split		: 1,
-			force_static_prot	: 1,
-			force_flush_all		: 1;
-	struct page	**pages;
-};
-
  enum cpa_warn {
  	CPA_CONFLICT,
  	CPA_PROTECT,
@@ -66,6 +49,13 @@ static const int cpa_warn_level = CPA_PROTECT;
   */
  static DEFINE_SPINLOCK(cpa_lock);

+static int default_set_memory_enc(unsigned long addr, int numpages, 
bool enc)
+{
+	return 0;
+}
+
+DEFINE_STATIC_CALL(x86_set_memory_enc, default_set_memory_enc);
+
  #define CPA_FLUSHTLB 1
  #define CPA_ARRAY 2
  #define CPA_PAGES_ARRAY 4
@@ -357,7 +347,7 @@ static void __cpa_flush_tlb(void *data)
  		flush_tlb_one_kernel(fix_addr(__cpa_addr(cpa, i)));
  }

-static void cpa_flush(struct cpa_data *data, int cache)
+void cpa_flush(struct cpa_data *data, int cache)
  {
  	struct cpa_data *cpa = data;
  	unsigned int i;
@@ -1587,8 +1577,6 @@ static int __change_page_attr(struct cpa_data 
*cpa, int primary)
  	return err;
  }

-static int __change_page_attr_set_clr(struct cpa_data *cpa, int 
checkalias);
-
  static int cpa_process_alias(struct cpa_data *cpa)
  {
  	struct cpa_data alias_cpa;
@@ -1646,7 +1634,7 @@ static int cpa_process_alias(struct cpa_data *cpa)
  	return 0;
  }

-static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
+int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
  {
  	unsigned long numpages = cpa->numpages;
  	unsigned long rempages = numpages;
@@ -1982,45 +1970,7 @@ int set_memory_global(unsigned long addr, int 
numpages)

  static int __set_memory_enc_dec(unsigned long addr, int numpages, bool 
enc)
  {
-	struct cpa_data cpa;
-	int ret;
-
-	/* Nothing to do if memory encryption is not active */
-	if (!mem_encrypt_active())
-		return 0;
-
-	/* Should not be working on unaligned addresses */
-	if (WARN_ONCE(addr & ~PAGE_MASK, "misaligned address: %#lx\n", addr))
-		addr &= PAGE_MASK;
-
-	memset(&cpa, 0, sizeof(cpa));
-	cpa.vaddr = &addr;
-	cpa.numpages = numpages;
-	cpa.mask_set = enc ? __pgprot(_PAGE_ENC) : __pgprot(0);
-	cpa.mask_clr = enc ? __pgprot(0) : __pgprot(_PAGE_ENC);
-	cpa.pgd = init_mm.pgd;
-
-	/* Must avoid aliasing mappings in the highmem code */
-	kmap_flush_unused();
-	vm_unmap_aliases();
-
-	/*
-	 * Before changing the encryption attribute, we need to flush caches.
-	 */
-	cpa_flush(&cpa, !this_cpu_has(X86_FEATURE_SME_COHERENT));
-
-	ret = __change_page_attr_set_clr(&cpa, 1);
-
-	/*
-	 * After changing the encryption attribute, we need to flush TLBs again
-	 * in case any speculative TLB caching occurred (but no need to flush
-	 * caches again).  We could just use cpa_flush_all(), but in case TLB
-	 * flushing gets optimized in the cpa_flush() path use the same logic
-	 * as above.
-	 */
-	cpa_flush(&cpa, 0);
-
-	return ret;
+	return static_call(x86_set_memory_enc)(addr, numpages, enc);
  }

  int set_memory_encrypted(unsigned long addr, int numpages)