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Re: [PATCH RFCv2 12/15] xen/arm: add Persistent Map (PMAP) infrastructure

Hi Stefano,

On 15/05/2021 00:25, Stefano Stabellini wrote:
On Sun, 25 Apr 2021, Julien Grall wrote:
From: Wei Liu <wei.liu2@xxxxxxxxxx>
+extern lpae_t xen_fixmap[LPAE_ENTRIES];
+void *__init pmap_map(mfn_t mfn)
+    unsigned long flags;
+    unsigned int idx;
+    vaddr_t linear;
+    unsigned int slot;
+    lpae_t *entry, pte;
+    BUILD_BUG_ON(sizeof(inuse) * BITS_PER_LONG < NUM_FIX_PMAP);
+    ASSERT(system_state < SYS_STATE_smp_boot);

One small concern here is that we have been using SYS_STATE_early_boot
to switch implementation of things like xen_map_table. Between
SYS_STATE_early_boot and SYS_STATE_smp_boot there is SYS_STATE_boot.

I guess I am wondering if instead of three potentially different mapping
functions (<= SYS_STATE_early_boot, < SYS_STATE_smp_boot, >=
SYS_STATE_smp_boot) we can get away with only two?

This is more flexible than the existing method to map memory when state == SYS_STATE_early_boot. If you look at the next patch (#13), you will see that there will be only two method to map memory.


diff --git a/xen/include/asm-arm/pmap.h b/xen/include/asm-arm/pmap.h
new file mode 100644
index 000000000000..8e1dce93f8e4
--- /dev/null
+++ b/xen/include/asm-arm/pmap.h
@@ -0,0 +1,10 @@
+#ifndef __ASM_PMAP_H__
+#define __ARM_PMAP_H__


I will fix it.

+/* Large enough for mapping 5 levels of page tables with some headroom */
+#define NUM_FIX_PMAP 8
+void *pmap_map(mfn_t mfn);
+void pmap_unmap(const void *p);

+#endif /* __ASM_PMAP_H__ */


Julien Grall



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