Hi,
On 22/07/2024 18:09, Oleksii Kurochko wrote:
On Mon, 2024-07-22 at 15:48 +0100, Julien Grall wrote:
Hi,
On 22/07/2024 15:44, Oleksii Kurochko wrote:
On Mon, 2024-07-22 at 14:54 +0200, Jan Beulich wrote:
On 12.07.2024 18:22, Oleksii Kurochko wrote:
--- /dev/null
+++ b/xen/arch/riscv/include/asm/pmap.h
@@ -0,0 +1,28 @@
+#ifndef __ASM_PMAP_H__
+#define __ASM_PMAP_H__
+
+#include <xen/bug.h>
+#include <xen/mm.h>
+
+#include <asm/fixmap.h>
+
+static inline void arch_pmap_map(unsigned int slot, mfn_t mfn)
+{
+ pte_t *entry = &xen_fixmap[slot];
+ pte_t pte;
+
+ ASSERT(!pte_is_valid(*entry));
+
+ pte = mfn_to_xen_entry(mfn, PAGE_HYPERVISOR_RW);
+ pte.pte |= PTE_LEAF_DEFAULT;
+ write_pte(entry, pte);
+}
+
+static inline void arch_pmap_unmap(unsigned int slot)
+{
+ pte_t pte = {};
+
+ write_pte(&xen_fixmap[slot], pte);
+}
Why are these not using set_fixmap() / clear_fixmap()
respectively?
They haven't been introduced yet. And I thought that these fucntion
are
used only in pmap_{un}map() and that is the reason why I decided to
not
introduce them. But while writing the answer on another comment, I
found other places where set_fixmap() / clear_fixmap() are used, so
I
will introduce them and reuse here.
I am guessing you are going to implement set_fixmap()/clear_fixmap()
using map_pages_to_xen(). If so, for early boot you are going to end
up
in a circular loop because map_pages_to_xen() will likely use pmap()
which will call set_fixmap().
I am going to implement that in the following way as I faced the
described by you issue when I first time tried to implement it using
map_pages_to_xen():
What's wrong with keeping the arch_pmap_*() as-is and call
map_pages_to_xen() in the fixmap?
At least this would be consistent with what other architectures does and
less risky (see below).
/* Map a 4k page in a fixmap entry */
void set_fixmap(unsigned map, mfn_t mfn, unsigned int flags)
{
pte_t pte;
pte = mfn_to_xen_entry(mfn, flags);
pte.pte |= PTE_LEAF_DEFAULT;
write_pte(&xen_fixmap[pt_index(0, FIXMAP_ADDR(map))], pte);
It would be saner to check if you are not overwriting any existing
mapping as otherwise you will probably need a TLB flush.
}
/* Remove a mapping from a fixmap entry */
void clear_fixmap(unsigned map)
{
pte_t pte = {0};
write_pte(&xen_fixmap[pt_index(0, FIXMAP_ADDR(map))], pte);
Don't you need a TLB flush?
Cheers,
--
Julien Grall
