On 05.11.19 02:37, Dan Williams wrote:
On Thu, Oct 24, 2019 at 5:10 AM David Hildenbrand <[email protected]> wrote:
Right now, ZONE_DEVICE memory is always set PG_reserved. We want to
change that.
KVM has this weird use case that you can map anything from /dev/mem
into the guest. pfn_valid() is not a reliable check whether the memmap
was initialized and can be touched. pfn_to_online_page() makes sure
that we have an initialized memmap (and don't have ZONE_DEVICE memory).
Rewrite kvm_is_mmio_pfn() to make sure the function produces the
same result once we stop setting ZONE_DEVICE pages PG_reserved.
Cc: Paolo Bonzini <[email protected]>
Cc: "Radim Krčmář" <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: KarimAllah Ahmed <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Dan Williams <[email protected]>
Signed-off-by: David Hildenbrand <[email protected]>
---
arch/x86/kvm/mmu.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 24c23c66b226..f03089a336de 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2962,20 +2962,25 @@ static bool mmu_need_write_protect(struct kvm_vcpu
*vcpu, gfn_t gfn,
static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
{
+ struct page *page = pfn_to_online_page(pfn);
+
+ /*
+ * ZONE_DEVICE pages are never online. Online pages that are reserved
+ * either indicate the zero page or MMIO pages.
+ */
+ if (page)
+ return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn));
+
+ /*
+ * Anything with a valid (but not online) memmap could be ZONE_DEVICE.
+ * Treat only UC/UC-/WC pages as MMIO.
You might clarify that ZONE_DEVICE pages that belong to WB cacheable
pmem have the correct memtype established by devm_memremap_pages().
/*
* Anything with a valid (but not online) memmap could be ZONE_DEVICE.
* Treat only UC/UC-/WC pages as MMIO. devm_memremap_pages() established
* the correct memtype for WB cacheable ZONE_DEVICE pages.
*/
Thanks!
Other than that, feel free to add:
Reviewed-by: Dan Williams <[email protected]>
--
Thanks,
David / dhildenb
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