From: mhkelley58@gmail.com
To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
kirill.shutemov@linux.intel.com, kys@microsoft.com,
haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com,
luto@kernel.org, peterz@infradead.org, akpm@linux-foundation.org,
urezki@gmail.com, hch@infradead.org, lstoakes@gmail.com,
thomas.lendacky@amd.com, ardb@kernel.org, jroedel@suse.de,
seanjc@google.com, rick.p.edgecombe@intel.com,
sathyanarayanan.kuppuswamy@linux.intel.com,
linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev,
linux-hyperv@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v2 2/8] x86/mm: Don't do a TLB flush if changing a PTE that isn't marked present
Date: Tue, 21 Nov 2023 13:20:10 -0800 [thread overview]
Message-ID: <20231121212016.1154303-3-mhklinux@outlook.com> (raw)
In-Reply-To: <20231121212016.1154303-1-mhklinux@outlook.com>
From: Michael Kelley <mhklinux@outlook.com>
The core function __change_page_attr() currently sets up a TLB flush if
a PTE is changed. But if the old value of the PTE doesn't include the
PRESENT flag, the PTE won't be in the TLB, so a flush isn't needed.
Avoid an unnecessary TLB flush by conditioning the flush on the old
PTE value including PRESENT. This change improves the performance of
functions like set_memory_p() by avoiding the flush if the memory range
was previously all not present.
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
---
arch/x86/mm/pat/set_memory.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 8e19796e7ce5..d7ef8d312a47 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1636,7 +1636,10 @@ static int __change_page_attr(struct cpa_data *cpa, int primary)
*/
if (pte_val(old_pte) != pte_val(new_pte)) {
set_pte_atomic(kpte, new_pte);
- cpa->flags |= CPA_FLUSHTLB;
+
+ /* If old_pte isn't present, it's not in the TLB */
+ if (pte_present(old_pte))
+ cpa->flags |= CPA_FLUSHTLB;
}
cpa->numpages = 1;
return 0;
--
2.25.1
next prev parent reply other threads:[~2023-11-21 21:20 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-21 21:20 [PATCH v2 0/8] x86/coco: Mark CoCo VM pages not present when changing encrypted state mhkelley58
2023-11-21 21:20 ` [PATCH v2 1/8] x86/coco: Use slow_virt_to_phys() in page transition hypervisor callbacks mhkelley58
2023-11-21 21:20 ` mhkelley58 [this message]
2023-11-27 22:21 ` [PATCH v2 2/8] x86/mm: Don't do a TLB flush if changing a PTE that isn't marked present Edgecombe, Rick P
2023-11-28 17:34 ` Michael Kelley
2023-11-21 21:20 ` [PATCH v2 3/8] x86/mm: Remove "static" from vmap_pages_range() mhkelley58
2023-11-22 6:26 ` Christoph Hellwig
2023-11-23 0:24 ` Michael Kelley
2023-11-23 7:32 ` Christoph Hellwig
2023-11-27 1:06 ` Michael Kelley
2023-11-21 21:20 ` [PATCH v2 4/8] x86/sev: Enable PVALIDATE for PFNs without a valid virtual address mhkelley58
2023-11-27 21:38 ` Edgecombe, Rick P
2023-11-28 18:08 ` Michael Kelley
2023-11-28 18:59 ` Edgecombe, Rick P
2023-12-12 18:35 ` Michael Kelley
2023-11-21 21:20 ` [PATCH v2 5/8] x86/mm: Mark CoCo VM pages not present while changing encrypted state mhkelley58
2023-11-21 21:20 ` [PATCH v2 6/8] x86/mm: Merge CoCo prepare and finish hypervisor callbacks mhkelley58
2023-11-21 21:20 ` [PATCH v2 7/8] x86/mm: Remove unnecessary call layer for __set_memory_enc_pgtable() mhkelley58
2023-11-21 21:20 ` [PATCH v2 8/8] x86/mm: Add comments about errors in set_memory_decrypted()/encrypted() mhkelley58
2023-11-24 10:06 ` [PATCH v2 0/8] x86/coco: Mark CoCo VM pages not present when changing encrypted state kirill.shutemov
2023-11-28 19:12 ` Michael Kelley
2023-11-29 15:10 ` kirill.shutemov
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