linux-kernel - Re: [PATCH v14 03/13] x86/mm: add INVLPGB support code

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Message-ID: <20250304161901.GCZ8cn9d252LTzThpI@fat_crate.local>
Date: Tue, 4 Mar 2025 17:19:01 +0100
From: Borislav Petkov <bp@...en8.de>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Rik van Riel <riel@...riel.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	dave.hansen@...ux.intel.com, zhengqi.arch@...edance.com,
	nadav.amit@...il.com, thomas.lendacky@....com, kernel-team@...a.com,
	linux-mm@...ck.org, akpm@...ux-foundation.org, jackmanb@...gle.com,
	jannh@...gle.com, mhklinux@...look.com, andrew.cooper3@...rix.com,
	Manali.Shukla@....com, mingo@...nel.org
Subject: Re: [PATCH v14 03/13] x86/mm: add INVLPGB support code

On Tue, Mar 04, 2025 at 07:10:13AM -0800, Dave Hansen wrote:
> So, we could have the enum be totally divorced from the hardware type:
> 
> 	NO_STRIDE,
> 	PTE_STRIDE,
> 	PMD_STRIDE

How about we completely hide that NO_STRIDE thing and do a __invlpgb_all()
"sub-helper" which is basically telling you it is invalidating all kinds of
TLB entries and stride does not apply there:

---

diff --git a/arch/x86/include/asm/tlb.h b/arch/x86/include/asm/tlb.h
index e8561a846754..361b3dde2656 100644
--- a/arch/x86/include/asm/tlb.h
+++ b/arch/x86/include/asm/tlb.h
@@ -66,6 +66,12 @@ static inline void __invlpgb(unsigned long asid, unsigned long pcid,
 	asm volatile(".byte 0x0f, 0x01, 0xfe" :: "a" (rax), "c" (ecx), "d" (edx));
 }
 
+static inline void __invlpgb_all(unsigned long asid, unsigned long pcid,
+				 unsigned long addr, u16 nr_pages, u8 flags)
+{
+	__invlpgb(asid, pcid, addr, nr_pages, 0, flags);
+}
+
 static inline void __tlbsync(void)
 {
 	/*
@@ -84,6 +90,8 @@ static inline void __tlbsync(void)
 static inline void __invlpgb(unsigned long asid, unsigned long pcid,
 			     unsigned long addr, u16 nr_pages,
 			     enum addr_stride s, u8 flags) { }
+static inline void __invlpgb_all(unsigned long asid, unsigned long pcid,
+				 unsigned long addr, u16 nr_pages, u8 flags) { }
 static inline void __tlbsync(void) { }
 #endif
 
@@ -121,7 +129,7 @@ static inline void __invlpgb_flush_user_nr_nosync(unsigned long pcid,
 /* Flush all mappings for a given PCID, not including globals. */
 static inline void __invlpgb_flush_single_pcid_nosync(unsigned long pcid)
 {
-	__invlpgb(0, pcid, 0, 1, PTE_STRIDE, INVLPGB_FLAG_PCID);
+	__invlpgb_all(0, pcid, 0, 1, INVLPGB_FLAG_PCID);
 }
 
 /* Flush all mappings, including globals, for all PCIDs. */
@@ -134,7 +142,7 @@ static inline void invlpgb_flush_all(void)
 	 * as it is cheaper.
 	 */
 	guard(preempt)();
-	__invlpgb(0, 0, 0, 1, PTE_STRIDE, INVLPGB_FLAG_INCLUDE_GLOBAL);
+	__invlpgb_all(0, 0, 0, 1, INVLPGB_FLAG_INCLUDE_GLOBAL);
 	__tlbsync();
 }
 
@@ -148,7 +156,7 @@ static inline void __invlpgb_flush_addr_nosync(unsigned long addr, u16 nr)
 static inline void invlpgb_flush_all_nonglobals(void)
 {
 	guard(preempt)();
-	__invlpgb(0, 0, 0, 1, PTE_STRIDE, INVLPGB_MODE_ALL_NONGLOBALS);
+	__invlpgb_all(0, 0, 0, 1, INVLPGB_MODE_ALL_NONGLOBALS);
 	__tlbsync();
 }
 #endif /* _ASM_X86_TLB_H */

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette