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[PATCH] x86/shadow: Drop dubious lastpage diagnostic
- To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 20 Jan 2023 11:45:56 +0000
- Authentication-results: esa4.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none
- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>
- Delivery-date: Fri, 20 Jan 2023 11:46:35 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
This is a global variable (actually 3, one per GUEST_PAGING_LEVEL), operated
on using atomics only (with no regard to what else shares the same cacheline),
which emits a diagnostic (in debug builds only) without changing any program
behaviour.
Based on read-only p2m types including logdirty, this diagnostic can be
tripped by entirely legitimate guest behaviour.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
---
xen/arch/x86/mm/shadow/multi.c | 7 -------
1 file changed, 7 deletions(-)
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 8b3e678fa0fa..3b06cfaf9a5a 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -2597,14 +2597,7 @@ static int cf_check sh_page_fault(
/* Ignore attempts to write to read-only memory. */
if ( p2m_is_readonly(p2mt) && (ft == ft_demand_write) )
- {
- static unsigned long lastpage;
- if ( xchg(&lastpage, va & PAGE_MASK) != (va & PAGE_MASK) )
- gdprintk(XENLOG_DEBUG, "guest attempted write to read-only memory"
- " page. va page=%#lx, mfn=%#lx\n",
- va & PAGE_MASK, mfn_x(gmfn));
goto emulate_readonly; /* skip over the instruction */
- }
/* In HVM guests, we force CR0.WP always to be set, so that the
* pagetables are always write-protected. If the guest thinks
--
2.11.0
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