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

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On 2/21/22 11:41, Kirill A. Shutemov wrote:
On Wed, Feb 16, 2022 at 10:04:57AM -0600, Brijesh Singh wrote:
@@ -287,6 +301,7 @@ struct x86_platform_ops {
  	struct x86_legacy_features legacy;
  	void (*set_legacy_features)(void);
  	struct x86_hyper_runtime hyper;
+	struct x86_guest guest;
  };

I used 'cc' instead of 'guest'. 'guest' looks too generic.

I am fine with either of them.


Also, I'm not sure why not to use pointer to ops struct instead of stroing
them directly in x86_platform. Yes, it is consistent with 'hyper', but I
don't see it as a strong argument.

index b4072115c8ef..a55477a6e578 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -2012,8 +2012,15 @@ static int __set_memory_enc_pgtable(unsigned long addr, int numpages, bool enc)
  	 */
  	cpa_flush(&cpa, !this_cpu_has(X86_FEATURE_SME_COHERENT));
+ /* Notify HV that we are about to set/clr encryption attribute. */
+	x86_platform.guest.enc_status_change_prepare(addr, numpages, enc);
+
  	ret = __change_page_attr_set_clr(&cpa, 1);

This doesn't cover difference in flushing requirements. Can we get it too?


Yes, we can work to include that too.

+ /* Notify HV that we have succesfully set/clr encryption attribute. */
+	if (!ret)
+		x86_platform.guest.enc_status_change_finish(addr, numpages, enc);
+

Any particular reason you moved it above cpa_flush()? I don't think it
makes a difference for TDX, but still.


It does not make any difference for the SNP as well. We can keep it where it was.


  	/*
  	 * After changing the encryption attribute, we need to flush TLBs again
  	 * in case any speculative TLB caching occurred (but no need to flush
@@ -2023,12 +2030,6 @@ static int __set_memory_enc_pgtable(unsigned long addr, int numpages, bool enc)
  	 */
  	cpa_flush(&cpa, 0);
- /*
-	 * Notify hypervisor that a given memory range is mapped encrypted
-	 * or decrypted.
-	 */
-	notify_range_enc_status_changed(addr, numpages, enc);
-
  	return ret;
  }
--
2.25.1






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