[PATCH v15 03/11] x86/mm: Add INVLPGB support code

[Borislav Petkov]

From: Rik van Riel <riel@xxxxxxxxxxx>

Add helper functions and definitions needed to use broadcast TLB
invalidation on AMD CPUs.

  [ bp:
      - Cleanup commit message
      - Improve and expand comments
      - push the preemption guards inside the invlpgb* helpers
      - merge improvements from dhansen
      - add !CONFIG_BROADCAST_TLB_FLUSH function stubs because Clang
	can't do DCE properly yet and looks at the inline asm and
	complains about it getting a u64 argument on 32-bit code ]

Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/20250226030129.530345-4-riel@xxxxxxxxxxx
---
 arch/x86/include/asm/tlb.h | 126 +++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)

diff --git a/arch/x86/include/asm/tlb.h b/arch/x86/include/asm/tlb.h
index 77f52bc1578a..8ffcae7beb55 100644
--- a/arch/x86/include/asm/tlb.h
+++ b/arch/x86/include/asm/tlb.h
@@ -6,6 +6,9 @@
 static inline void tlb_flush(struct mmu_gather *tlb);
 
 #include <asm-generic/tlb.h>
+#include <linux/kernel.h>
+#include <vdso/bits.h>
+#include <vdso/page.h>
 
 static inline void tlb_flush(struct mmu_gather *tlb)
 {
@@ -25,4 +28,127 @@ static inline void invlpg(unsigned long addr)
 	asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
 }
 
+enum addr_stride {
+	PTE_STRIDE = 0,
+	PMD_STRIDE = 1
+};
+
+#ifdef CONFIG_BROADCAST_TLB_FLUSH
+/*
+ * INVLPGB does broadcast TLB invalidation across all the CPUs in the system.
+ *
+ * The INVLPGB instruction is weakly ordered, and a batch of invalidations can
+ * be done in a parallel fashion.
+ *
+ * The instruction takes the number of extra pages to invalidate, beyond
+ * the first page, while __invlpgb gets the more human readable number of
+ * pages to invalidate.
+ *
+ * The bits in rax[0:2] determine respectively which components of the address
+ * (VA, PCID, ASID) get compared when flushing. If neither bits are set, *any*
+ * address in the specified range matches.
+ *
+ * TLBSYNC is used to ensure that pending INVLPGB invalidations initiated from
+ * this CPU have completed.
+ */
+static inline void __invlpgb(unsigned long asid, unsigned long pcid,
+			     unsigned long addr, u16 nr_pages,
+			     enum addr_stride stride, u8 flags)
+{
+	u32 edx = (pcid << 16) | asid;
+	u32 ecx = (stride << 31) | (nr_pages - 1);
+	u64 rax = addr | flags;
+
+	/* The low bits in rax are for flags. Verify addr is clean. */
+	VM_WARN_ON_ONCE(addr & ~PAGE_MASK);
+
+	/* INVLPGB; supported in binutils >= 2.36. */
+	asm volatile(".byte 0x0f, 0x01, 0xfe" :: "a" (rax), "c" (ecx), "d" (edx));
+}
+
+static inline void __tlbsync(void)
+{
+	/*
+	 * TLBSYNC waits for INVLPGB instructions originating on the same CPU
+	 * to have completed. Print a warning if the task has been migrated,
+	 * and might not be waiting on all the INVLPGBs issued during this TLB
+	 * invalidation sequence.
+	 */
+	cant_migrate();
+
+	/* TLBSYNC: supported in binutils >= 0.36. */
+	asm volatile(".byte 0x0f, 0x01, 0xff" ::: "memory");
+}
+#else
+/* Some compilers (I'm looking at you clang!) simply can't do DCE */
+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 __tlbsync(void) { }
+#endif
+
+/*
+ * INVLPGB can be targeted by virtual address, PCID, ASID, or any combination
+ * of the three. For example:
+ * - FLAG_VA | FLAG_INCLUDE_GLOBAL: invalidate all TLB entries at the address
+ * - FLAG_PCID:			    invalidate all TLB entries matching the PCID
+ *
+ * The first is used to invalidate (kernel) mappings at a particular
+ * address across all processes.
+ *
+ * The latter invalidates all TLB entries matching a PCID.
+ */
+#define INVLPGB_FLAG_VA			BIT(0)
+#define INVLPGB_FLAG_PCID		BIT(1)
+#define INVLPGB_FLAG_ASID		BIT(2)
+#define INVLPGB_FLAG_INCLUDE_GLOBAL	BIT(3)
+#define INVLPGB_FLAG_FINAL_ONLY		BIT(4)
+#define INVLPGB_FLAG_INCLUDE_NESTED	BIT(5)
+
+/* The implied mode when all bits are clear: */
+#define INVLPGB_MODE_ALL_NONGLOBALS	0UL
+
+static inline void invlpgb_flush_user_nr_nosync(unsigned long pcid,
+						unsigned long addr,
+						u16 nr, bool stride)
+{
+	enum addr_stride str = stride ? PMD_STRIDE : PTE_STRIDE;
+	u8 flags = INVLPGB_FLAG_PCID | INVLPGB_FLAG_VA;
+
+	__invlpgb(0, pcid, addr, nr, str, flags);
+}
+
+/* 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);
+}
+
+/* Flush all mappings, including globals, for all PCIDs. */
+static inline void invlpgb_flush_all(void)
+{
+	/*
+	 * TLBSYNC at the end needs to make sure all flushes done on the
+	 * current CPU have been executed system-wide. Therefore, make
+	 * sure nothing gets migrated in-between but disable preemption
+	 * as it is cheaper.
+	 */
+	guard(preempt)();
+	__invlpgb(0, 0, 0, 1, PTE_STRIDE, INVLPGB_FLAG_INCLUDE_GLOBAL);
+	__tlbsync();
+}
+
+/* Flush addr, including globals, for all PCIDs. */
+static inline void invlpgb_flush_addr_nosync(unsigned long addr, u16 nr)
+{
+	__invlpgb(0, 0, addr, nr, PTE_STRIDE, INVLPGB_FLAG_INCLUDE_GLOBAL);
+}
+
+/* Flush all mappings for all PCIDs except globals. */
+static inline void invlpgb_flush_all_nonglobals(void)
+{
+	guard(preempt)();
+	__invlpgb(0, 0, 0, 1, PTE_STRIDE, INVLPGB_MODE_ALL_NONGLOBALS);
+	__tlbsync();
+}
 #endif /* _ASM_X86_TLB_H */
-- 
2.43.0