From: Janosch Frank <frankja@linux.ibm.com>
To: kvm@vger.kernel.org
Cc: borntraeger@de.ibm.com, david@redhat.com,
linux-s390@vger.kernel.org, imbrenda@linux.ibm.com
Subject: [PATCH 05/14] s390/mm: Split huge pages when migrating
Date: Wed, 13 Jan 2021 09:41:04 +0000 [thread overview]
Message-ID: <20210113094113.133668-6-frankja@linux.ibm.com> (raw)
In-Reply-To: <20210113094113.133668-1-frankja@linux.ibm.com>
Right now we mark the huge page that is being written to as dirty
although only a single byte may have changed. This means we have to
migrate 1MB although only a very limited amount of memory in that
range might be dirty.
To speed up migration this patch splits up write protected huge pages
into normal pages. The protection for the normal pages is only removed
for the page that caused the fault.
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
---
arch/s390/mm/gmap.c | 34 ++++++++++++++++++++++++++++------
1 file changed, 28 insertions(+), 6 deletions(-)
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 41a5bbbc59e6..d8c9b295294b 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -532,6 +532,9 @@ void gmap_unlink(struct mm_struct *mm, unsigned long *table,
static void gmap_pmdp_xchg(struct gmap *gmap, pmd_t *old, pmd_t new,
unsigned long gaddr);
+static void gmap_pmd_split(struct gmap *gmap, unsigned long gaddr,
+ pmd_t *pmdp, struct page *page);
+
/**
* gmap_link - set up shadow page tables to connect a host to a guest address
* @gmap: pointer to guest mapping meta data structure
@@ -547,12 +550,12 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
{
struct mm_struct *mm;
unsigned long *table;
+ struct page *page = NULL;
spinlock_t *ptl;
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
- u64 unprot;
pte_t *ptep;
int rc;
@@ -600,6 +603,7 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
/* Are we allowed to use huge pages? */
if (pmd_large(*pmd) && !gmap->mm->context.allow_gmap_hpage_1m)
return -EFAULT;
+retry_split:
/* Link gmap segment table entry location to page table. */
rc = radix_tree_preload(GFP_KERNEL_ACCOUNT);
if (rc)
@@ -627,10 +631,25 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
spin_unlock(&gmap->guest_table_lock);
} else if (*table & _SEGMENT_ENTRY_PROTECT &&
!(pmd_val(*pmd) & _SEGMENT_ENTRY_PROTECT)) {
- unprot = (u64)*table;
- unprot &= ~_SEGMENT_ENTRY_PROTECT;
- unprot |= _SEGMENT_ENTRY_GMAP_UC;
- gmap_pmdp_xchg(gmap, (pmd_t *)table, __pmd(unprot), gaddr);
+ if (page) {
+ gmap_pmd_split(gmap, gaddr, (pmd_t *)table, page);
+ page = NULL;
+ } else {
+ spin_unlock(ptl);
+ ptl = NULL;
+ radix_tree_preload_end();
+ page = page_table_alloc_pgste(mm);
+ if (!page)
+ rc = -ENOMEM;
+ else
+ goto retry_split;
+ }
+ /*
+ * The split moves over the protection, so we still
+ * need to unprotect.
+ */
+ ptep = pte_offset_map((pmd_t *)table, vmaddr);
+ ptep_remove_protection_split(mm, ptep, vmaddr);
} else if (gmap_pmd_is_split((pmd_t *)table)) {
/*
* Split pmds are somewhere in-between a normal and a
@@ -642,7 +661,10 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
if (pte_val(*ptep) & _PAGE_PROTECT)
ptep_remove_protection_split(mm, ptep, vmaddr);
}
- spin_unlock(ptl);
+ if (page)
+ page_table_free_pgste(page);
+ if (ptl)
+ spin_unlock(ptl);
radix_tree_preload_end();
return rc;
}
--
2.27.0
next prev parent reply other threads:[~2021-01-13 9:42 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 9:40 [PATCH 00/14] KVM: s390: Add huge page VSIE support Janosch Frank
2021-01-13 9:41 ` [PATCH 01/14] s390/mm: Code cleanups Janosch Frank
2021-01-13 9:41 ` [PATCH 02/14] s390/mm: Improve locking for huge page backings Janosch Frank
2021-01-13 9:41 ` [PATCH 03/14] s390/mm: Take locking out of gmap_protect_pte Janosch Frank
2021-01-13 9:41 ` [PATCH 04/14] s390/mm: split huge pages in GMAP when protecting Janosch Frank
2021-01-13 9:41 ` Janosch Frank [this message]
2021-01-13 9:41 ` [PATCH 06/14] s390/mm: Provide vmaddr to pmd notification Janosch Frank
2021-01-13 9:41 ` [PATCH 07/14] s390/mm: factor out idte global flush into gmap_idte_global Janosch Frank
2021-01-13 9:41 ` [PATCH 08/14] s390/mm: Make gmap_read_table EDAT1 compatible Janosch Frank
2021-01-13 9:41 ` [PATCH 09/14] s390/mm: Make gmap_protect_rmap " Janosch Frank
2021-01-13 9:41 ` [PATCH 10/14] s390/mm: Add simple ptep shadow function Janosch Frank
2021-01-13 9:41 ` [PATCH 11/14] s390/mm: Add gmap shadowing for large pmds Janosch Frank
2021-01-19 22:18 ` kernel test robot
2021-01-13 9:41 ` [PATCH 12/14] s390/mm: Add gmap lock classes Janosch Frank
2021-01-13 9:41 ` [PATCH 13/14] s390/mm: Pull pmd invalid check in gmap_pmd_op_walk Janosch Frank
2021-01-13 9:41 ` [PATCH 14/14] KVM: s390: Allow the VSIE to be used with huge pages Janosch Frank
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