diff mbox series

[1/5] x86/shim: map and unmap page tables in replace_va_mapping

Message ID 1acfafbd8ebada1538c9e06323ef0b3bf3f6897c.1584955616.git.hongyxia@amazon.com (mailing list archive)
State Superseded
Headers show
Series use new API for Xen page tables | expand

Commit Message

Hongyan Xia March 23, 2020, 9:41 a.m. UTC 
From: Wei Liu <wei.liu2@citrix.com>

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Hongyan Xia <hongyxia@amazon.com>
---
 xen/arch/x86/pv/shim.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

Comments

Jan Beulich April 1, 2020, 12:11 p.m. UTC | #1 
On 23.03.2020 10:41, Hongyan Xia wrote:
> --- a/xen/arch/x86/pv/shim.c
> +++ b/xen/arch/x86/pv/shim.c
> @@ -169,15 +169,19 @@ static void __init replace_va_mapping(struct domain *d, l4_pgentry_t *l4start,
>                                        unsigned long va, mfn_t mfn)
>  {
>      l4_pgentry_t *pl4e = l4start + l4_table_offset(va);
> -    l3_pgentry_t *pl3e = l4e_to_l3e(*pl4e) + l3_table_offset(va);
> -    l2_pgentry_t *pl2e = l3e_to_l2e(*pl3e) + l2_table_offset(va);
> -    l1_pgentry_t *pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(va);
> +    l3_pgentry_t *pl3e = map_l3t_from_l4e(*pl4e) + l3_table_offset(va);
> +    l2_pgentry_t *pl2e = map_l2t_from_l3e(*pl3e) + l2_table_offset(va);
> +    l1_pgentry_t *pl1e = map_l1t_from_l2e(*pl2e) + l1_table_offset(va);
>      struct page_info *page = mfn_to_page(l1e_get_mfn(*pl1e));
>  
>      put_page_and_type(page);
>  
>      *pl1e = l1e_from_mfn(mfn, (!is_pv_32bit_domain(d) ? L1_PROT
>                                                        : COMPAT_L1_PROT));
> +
> +    UNMAP_DOMAIN_PAGE(pl1e);
> +    UNMAP_DOMAIN_PAGE(pl2e);
> +    UNMAP_DOMAIN_PAGE(pl3e);
>  }

I disagree to an approach like this: Why have three pending mappings
when one at a time will do? Map-read/write-unmap three times is what
you want here, even if this is more code churn.

Jan
diff mbox series

Patch

diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index ed2ece8a8a..1229d5ffb3 100644
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -169,15 +169,19 @@  static void __init replace_va_mapping(struct domain *d, l4_pgentry_t *l4start,
                                       unsigned long va, mfn_t mfn)
 {
     l4_pgentry_t *pl4e = l4start + l4_table_offset(va);
-    l3_pgentry_t *pl3e = l4e_to_l3e(*pl4e) + l3_table_offset(va);
-    l2_pgentry_t *pl2e = l3e_to_l2e(*pl3e) + l2_table_offset(va);
-    l1_pgentry_t *pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(va);
+    l3_pgentry_t *pl3e = map_l3t_from_l4e(*pl4e) + l3_table_offset(va);
+    l2_pgentry_t *pl2e = map_l2t_from_l3e(*pl3e) + l2_table_offset(va);
+    l1_pgentry_t *pl1e = map_l1t_from_l2e(*pl2e) + l1_table_offset(va);
     struct page_info *page = mfn_to_page(l1e_get_mfn(*pl1e));
 
     put_page_and_type(page);
 
     *pl1e = l1e_from_mfn(mfn, (!is_pv_32bit_domain(d) ? L1_PROT
                                                       : COMPAT_L1_PROT));
+
+    UNMAP_DOMAIN_PAGE(pl1e);
+    UNMAP_DOMAIN_PAGE(pl2e);
+    UNMAP_DOMAIN_PAGE(pl3e);
 }
 
 static void evtchn_reserve(struct domain *d, unsigned int port)